The Final Report of the "Study Group on Broadcasting
and Audio-Visual Sensory Perception"

June, 1998


This study group was set up immediately after the "Pocket Monster" incident that occurred on December 16, 1997. The purpose of the study is to help ensure appropriate broadcasting for viewers and to improve the viewing environment in today's advanced information society. It focused on studying mainly the audiovisual and physiological effects of the broadcast programs. The group consists of specialists in the fields of engineering, medicine, psychology, media theory, broadcasting, producers, etc., and conducted research on the issue from carious aspects.
The "Pocket Monster" has been the first case to draw the social attention to the issue, that the advancement of visual images can be harmful to the human body. Therefore, the study group has discussed the effects of audio-visual image techniques on the human body's central nervous system, which has not been studied in detail in the past.
Since its establishment, the study group has reviewed the image display methods of television and submitted an interim report concerning the celluloid animation display methods. The purpose of this final report is to present the results obtained through further research on the other image display methods that was conducted after the interim report was submitted.

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Chapter 1. Background and Principles of Research

This chapter refers to the background of the formation of the study group (summary of issues concerning the animation program "Pocket Monster" story #38, display techniques used in this story, reactions of the related organization, etc.). The views of this study group based on our discussions are also presented.

1. Background

(1) Animation program, story #38 of "Pocket Monster" and #25 of "YAT Anshin! Space Travel"

Pocket Monster (generally called "Pokemon") was released in February 1996 by Nintendo as a software for the portable video game "Game Boy". The story is about the adventures of its main character, Satoshi, who travels around and collects the monster characters called "Pocket Monsters". It has attracted a significant number of children, mainly elementary school students. It was also published as comic books. Furthermore, from April 1997, it was broadcast as an animation program "Pocket Monster" by Television Tokyo Channel 12 (starting at 6:30 p.m. on Tuesdays, aired by 6 of the network stations nationwide; the program was also syndicated to 31 stations). It was considered to have a high rating in its time slot.
On December 16, 1997 the "Pocket Monster" (story #38) was broadcast on these six stations (Hokkaido, Tokyo, Aichi, Osaka, Okayama-Kagawa, Fukuoka) and the rating of the program was 16.5% (in the Kanto region, surveyed by Video Research), and thus was watched by approximately 4.6 million households.
Some of the viewers who watched this program (mostly children) complained of nausea and some were hospitalized. Later it was discovered that the appearance of the symptoms occurred mainly around 6:50 p.m. As a result of watching this program, 685 people nationwide suffered symptoms and were taken to hospitals by ambulances (as of 5:00 p.m., December 17, 1997, according to Fire-Defense Agency). It is not certain how many viewers there were per household, however, assuming one viewer was watching the program in each of 4.6 million households, it can be said that 0.015% of the total viewers were sent to the hospitals.
Following this incident, syndication s were halted and the remaining of Television Tokyo Channel 12's network stations have stopped broadcasting this program.
It was also discovered in the later research that similar symptoms had occurred, although smaller in scale, during the airing of "YAT Anshin! Space Travel" story #25 on Saturday, March 29, 1997.

(2) Display Techniques of "Pocket Monster" Story #38

Story #38 of "Pocket Monster" in question, took place in a virtual world inside a computer. In order to stress the difference with the real world in the story, a method known as "transmitted light photographing (TLP)" (commonly called "paka-paka"), in which the background is lit up with strong flashes of light, was used frequently.
Many cases of seizures reported were said to occur at around 6:50 p.m. , when TLP was being shown for several seconds. It is assumed that the use of this imaging method caused the symptoms such as seizures. TLP is a technique that has been traditionally used in animation imaging.

(3) Broadcaster's Reaction: Determination of Causes and Formation of Guidelines

At Television Tokyo Channel 12, an "Animation Pocket Monster Internal Coordination Team" was set up in reaction to the incident. This term researched animation techniques, examined the problems in the technical aspect of the program and techniques used overseas. It is now drawing up the individual guidelines for producing animation programs.
The Broadcasting Standards Council of the National Association of Commercial Broadcasters in Japan considered the case seriously and stated that, "For the time being, in terms of visual imaging techniques, we will handle with extreme care the broadcasting of flashes, images of flashing lights, and rapidly changing lights as well as frequent use of very short images." Together with the statement, they established the "Special Section on the Imaging of Animation Programs" and the "Advisory Meeting on the Imaging of Animation Programs" within the Council that worked on specific guidelines. On the other hand, NHK also set up the "Animation Problems Discussion Project" in order to examine the effect of the special animation imaging techniques on viewers from medical and other aspects.
In addition, NHK and National Association of Commercial Broadcaster in Japan jointly established the voluntary guidelines for animation display techniques.
Considering the interim report submitted on April 6, 1997, NHK and National Association of Commercial Broadcaster jointly established "the Guidelines for the image display methods of animation and others".

(Reactions by NHK)
NHK reported the content of the Guidelines in the news and other promotion programs together with informing viewers of the favorable ways of viewing television in spots. Also NHK established its original enforcement regulation along with the Guidelines, as well as modifying the 'Criteria for Domestic Programs' by adding an item, stating that the effect of image display methods for human body should be taken into consideration. In addition, NHK decided to develop and introduce a device that will automatically determine at the production studio on whether the images of the program withstand the regulations set in the Guidelines.

(Reaction by National Association of Commercial Broadcaster)
NACB informed all of the affiliated companies of the Guidelines as well as sending copies to other related organizations and animation producers, which ended up with 15 organizations and 171 companies. Also NACB provided necessary materials to each of the broadcasters that promote understanding for the Guidelines for the purpose of urging them to establish their own enforcement regulations. Following the above, the Guidelines that were made jointly with NHK will be incorporated in the 'NACB Program Criteria Guide' to arouse attention to the effect of television images to children's bodies.

(Reaction by Television Tokyo Channel 12)
Television Tokyo Channel 12 established the 'Production Guidelines for Image Effect of Animation Programs' on April 9th and resumed broadcasting of Pocket Monster on 16th. It developed an animation checker which examines each animation whether its image display is appropriate to the Guidelines.

2. Principles of the Study Group

The Pocket Monster incident was the first outstanding case that showed that the advanced audiovisual imaging techniques can be harmful to human body.
The role of the study group is to prevent repetition of such incidents. Television programs, as well as other audio-visual media, provides essential information to the audience, while being the means of education, enlightenment, and entertainment, thus playing an important social, economical, and cultural role.
Concerning the above, therefore, it is extremely important to ensure the proper and safe environment for the television viewer.
The study group is expected to contribute to the further development of films and broadcasting in the era of multimedia and multichannels.
Especially the film industry is considered as an important part of the remarkably developing Japan's information and communications industry. Animation has been popular in Japan for many years among many age groups. As being called "anime" or "Japanimation", it also has been known worldwide. In terms of market share, Japanese animation accounts for 65% of the entire world market. It is thus extremely important to take responsibility to ensure the safety of visual imaging display in order for the world's audience to watch it safely.
Since many viewers of animation are children at various stages of growth, sufficient care should also be taken for their healthy growth.
Furthermore, we also decided to discuss what broadcasters should take into consideration and what are the appropriate administrative policies, taking into account the rapid progress of technology in the filming and information. To this end, a broad but detailed discussion encompassing the natural science, humanities, and the social science are necessary.
The results of the discussions conducted during a limited time period are summarized in the following pages.

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Chapter 2. Display Techniques of Images

Since the problem arose with a technique called TLP in story #38 of "Pocket Monster", this chapter will first explain the filming techniques in general (camera work, cell work, filming effects) and TLP filming, followed by the explanation of other techniques related to digital animation.

1. Filming techniques

(1) Celluloid Animation

Cell animation involves shooting separately-drawn cell pictures and background pictures combined in front of the camera frame by frame. The process can be separated into the four stages (camera work, cell work, filming effects, and scene changes) as described below. Also, as related to the incident, TLP is one of the filming effect techniques.

Camera work
Technique centered on moving the camera along the line

Names of the Techniques

Filming method

Pan Method of moving the base (background or cell)
Follow pan (attached pan) Method of changing the angle of the camera while following the movement of the object
Track up Track back Method of camera moving closer to or away from the object
Crane up Crane down Method which has the same effect as moving the camera up and down on a crane while moving both the object and the background
Picture rotation (spin) Method of designating the duration of the spin and rotating the base horizontally
Follow Method which has the same filming effect as the camera follows the object by moving the background or the cell
Multi gondola (multi level filming) Method of creating a stereoscopic effect by placing a special glass plate on the panel and placing the cell on top of it, filming it at the same time, and having one of them out of focus

Cell work
Technique using the movement or changes in background and cell pictures

Names of the Techniques

Filming method

Pull (slide) Method of sliding the cell or the background on the base with a fixed pull speed while moving
Rolling Method of repetition movement such as shaking within the slide of the cell (waves in the sea or the up-and-down motion of walking)
Picture movement Method of expressing vibration by shaking the base (ex. Earthquake)

Filming effects
Methods using camera functions

Names of the techniques

Filming method

Fade in (FI) Fade out (FO) Method of expressing an image appearing out of a dark scene and an image disappearing into darkness by changing the shutter aperture
Overlap Method of fading in the next cut by rewinding the footage filmed with FO
Strobe Method of creating quick overlaps of FI and FO
Super Method of rewinding the film, filming with appropriate exposure twice, and overlapping one scene on another
Overlay Method of overlapping one scene on another and ultimately adjusting to appropriate exposure (both pictures can be seen transparent)
Semi exposure Method of darkening unexposed portions with a dark mask (describes conditions where there are partial shades)
TLP Method of actually flashing light from below on film that is already exposed in order to express light more realistically (ordinarily done in super and overlaps special filters and color paraffin in order to give a running effect to light or some color)
Exposure differential Freely adjusts scenes with traces of white and black by changing camera exposure
Black scene and white scene Used when scenes are momentarily all black or all white (frequently used in the scenes of explosions)

Scene changes
Used in combination with other techniques in order to express changes in scenes or the passage of time.

Names of the techniques

Filming method

Wipe Iris in Iris out Scene changing method where shapes can be freely changed or created
Focus in Focus out Zooming into focus on purpose or vice versa
Wiping in Method of deleting little by little by reverse playing the footage from a fully drawn picture

Transmitted light photographing (TLP) is one of the special effects of celluloid animation filming. It is categorized into filming effects as stated above and the technique has existed since the early years of animation. The scene of flashing red and blue in the animation program "Pocket Monster" was created usint TLP.
TLP can flash brightly the entire screen or portions thereof by directly filming light. It is used to express light such as sunrays, flames, beam of light, lightning, water surfaces, and twinkling stars, which cannot be drawn by hand.
In the method, films on which cells are already filmed are rewound, light is shone from below, and they are filmed again in order to realistically express light. In order to give light a softer effect, the film is frequently shot with color paraffins and special filters. Depending on the number of frames of TLP (from one to several frames), there are differences in the effect of flashing on the entire screen or parts thereof.

References: Display techniques in TV images

  1. Display techniques in TV footage
    (1) The receiver creates images by horizontally scanning with electronic beams. There are two scanning methods: progressive scanning where scanning is done from top to bottom, and intermittent scanning where the first lines are scanned every other line and then images are completed in the second scanning. The present NTSC standard TV receivers use intermittent scanning.
    (2) The present NTSC standard creates a full image at 30 frames per second. The PAL standard used in Europe uses 25 frames per second.
    (3) A basic video field is scanned 60 times per second. In other words, 60 Hz (European PAL uses 50 scans per second).

  2. Changes from film to video
    (1) Celluloid animation filming is done mostly with film and ordinarily shot at 24 frames per second.
    (2) On the other hand, for NTSC standard television sets, one second consists of 30 frames. Therefore, then animation is broadcast over television, the number of frames must be adjusted. This adjustment is done by a machine automatically.

(2) Digital Animation

Present condition
The process of making celluloid animation is done by drawing the original picture on paper, copying it on a cell, putting color on it, and then filming it with background by camera. Digital animation is to carry out all of the above processes by computer, except for the first step of drawing the original picture.
Digital animation has rapidly spread among Japanese program producers recently. There are some producers that specialize in digital animation.
By digital animation, it is possible to make 100 cells per day, while celluloid animation can make only 30 cells per day. Concerning the efficiency, digital animation is expected to keep spreading from now on.

Outline of the work processes
After drawing the original picture just as celluloid animation, it is put into the computer as digital data using a scanner, arranged with color and gradation on the computer screen, and combined with background. This screen data is then transferred to videos by a recorder.

1) Make the Scenario
2) Make the Contes
3) Layout
4) Draw the Original Pictures
5) Put the Picture Data into Computer by a Scanner
6) Put colors by a Painter (software)
7) Combine Picture and Background on a Computer Screen
8) Transfer the Image to a Video Using a Recorder (D2, beta-com)
Compared to celluloid animation, digital animation is more efficient in the following features.
1) Paint is not Necessary
2) Easy to Modifying
3) Cell-less
4) No Need to Film the Cells One by One
Effect of Image Display
In terms of natural phenomenon (light, water, or wind) that is difficult to express in artificial images, digital animation makes it possible by filming the actual image, putting it in a computer as digital data, arranging its colors and brightness or using an effect software depending on the producer's creativity, and can make it more realistic than celluloid animation. As for the colors, they would never be limited as in the case of celluloid animation.
Therefore, digital animation is much more flexible than celluloid animation in terms of producing special effects such as TLP: thus producers must be more careful in display technique when using digital animation.

(3) Actual Filming

Techniques of Images Operation and Editing
The followings are the typical image operating methods and editing methods.

1) Typical image operating methods

Method of Image Operation


Panning Method of filming by swinging the camera back and forth with an appropriate speed
Tilting Method of filming by swinging the camera up and down
Zooming Method of filming by changing the focus distance of lenses Filing by zooming the object
Dory Method of filming by moving horizontally on the ground
Crane Method of filming the continuous images by moving the camera up and down

2) Typical image editing methods

Method of Image Editing


Cut Discontinuous change from one picture to another
Cutback Method of expressing two opposing pictures alternately by way of cut
Flash back Method of continuing short-term cutbacks
Montage Method of combining different shots with contrivance in order to express the whole story effectively
Wipe Method of changing pictures as the first picture gets drawn out and replaced with the second (right-left, up-down, center-periphery, etc.)
Dissolve Method of changing pictures by overlapping
Fade Fade in is the method of expressing a bright image appearing out of a dark scene and fade out is the method of expressing a dark image appearing out of a bright scene
Digital effect Special effect that becomes possible by digital imaging techniques for instance, zooming, separating, moving ,tilting or transforming

Effect of Image Display
Elements of image expression, namely 1) image operation (camera work, filming effect (camera position, camera angle, direction of camera movement and speed, contrast of brightness and darkness of the screen, etc.)) and 2) image editing, strongly depend on producers' experiential creativeness and therefore, there has not been any systematic research on the relationship between image display methods and their effect.
However, image is essentially an extrinsic stimulus to human body. Therefore, it has some effect to cerebrum which process visual information, depending on how it is displayed.
Some of the typical image expression methods and the their possibility of affecting human body are introduced in the following.
1) Display of "Continuous Change of Images"
Viewers are not actually moving their eyes, head and body to adjust, when the continuous change of images as visual attention moves up-down, right-left, distance and depth (panning, tilting, zooming, and dory) occurs, but rather they are replacing the visual images with actual body movement, which make it possible for display images to confuse the viewers.

2) Display of "Discontinuous Change of Images"
When discontinuous change of images (cut, cutback, flashback, and montage) occurs, viewers are immediately focusing and moving the eyes to the whole image on the screen. Therefore, it is possible to display images that may confuse the visual information processing of the viewers.

3) Display of "Acceleration of Image Change"
By accelerating the changing speed of images, it is possible to draw attention of the viewers to the scene or to make them tense. This method is called "Acceleration Montage".

4) Display of "Contrary-Time Images"
In order to perceive the display of images that goes against actual time, viewers need high level of perception mechanism. However, for the images that the viewers cannot perceive the relationship between the actual time and the displayed time, it is likely that they are confused. It is more likely especially for children to be confused, whose perceiving ability is not enough developed.

(4) CGI

Present condition
CGI (computer generated imagery) is an image that was created by a computer.
On the other hand, CG is a general term for techniques that create images or process image data by calculation.
As the computer processing technology has developed, CG has been frequently used for digitalization of image processing and therefore, CGI has also been widely spread.
CGI can make not only images that are impossible to create by actual filming, but also those that are more efficient, low-cost and realistic than actual filming and therefore, has become popular these days.

The following is a list of ways in which the CGI is being used.

Visualization of numerical data Display physical or social data (weather forecast, news flash of the vote counting of election) in visual images that draws clear understanding
Visualization of fictitious world Create a world of images that do not exist in reality
Visualization of world that is free from time Appearance of persons from the past or in the future
Possibility to change images Possibility to change scene, position, shape, movement of the object in any way as the producer wishes
Visualization of scenes that are impossible to create by actual filming Filming of the outer space, micro environment, dangerous zone, expensive or scarce object
Exaggeration Acting of characters that exaggerate human actions or emotional expression
New methods of image display Artistic images, interactive art

Effect of Image Display
CGI, including combination with actual images, can process images freely on a computer screen and also makes possible the image expressions as writing, trimming, various special effects and transformed animation as well as different shapes and colors.
Therefore, it has been made possible to realize expression of texture and depiction that are more realistic than the real thing, as its quality is so high that it is even impossible to distinguish between reality and fake.
This means that the technical aspect of the image displays that have been used in the actual filming and celluloid animation have stayed the same, but their quality has reached the high-level remarkably and will be spreading. Display methods of this quality will be able to exhibit further effects that will need sufficient consideration.

(5) Three-dimensional Images/VR

Present condition
As the techniques of the CG and the VR (virtual reality) have developed and spread, three-dimensional display and VR system have put to practical use. It made use of the three-dimensional visual function of human into the simulation systems.
This has occurred along with the growing need for computer designing as CAD, development of multi-personal synchronistic simulation device, medical diagnoses assisting devices, educational exhibition devices, etc.
However, three-dimensional images has extremely high level of reality and virtuality that can cause eyestrain, dizziness and vomiting, depending upon the viewing environment.

Three-dimensional Techniques (Three-dimensional Display and Others)
Since 1930's, anaglyph system and deflection glass system have been applied, as opposed to animation, and have developed as three-dimensional movies and television. Currently the three-dimensional television which does not use glasses are under development.
Anaglyph system is a three-dimensional image display system which creates three-dimensional view by keeping an appropriate vision difference between two images, as viewers watch dual image of red and blue on a screen wearing filtered glasses in the same colors.
As for the three-dimensional system without glasses, various systems are under research and development and will soon be in practical use. Examples are; system that uses special glasses called lenticular lenses, system that uses liquid crystal projector and three-dimensional display optical screen, and three-dimensional image created by hologram, etc.

VR (Virtual Reality)
VR (Virtual Reality) means things in fact and it can also mean imaginary reality. In the narrow sense, it is a general term for computer techniques that let the viewers to experience the imaginary reality created in a computer as if it is the reality.
Therefore, motion senses as the sense of equilibrium, the sense of speed, vibration as well as visual and auditory senses, interaction between motions of arms, fingers, neck and eyes with the imaginary reality, the sense of touch, repulsion, weight, softness, smell, temperature, wind are all very important. Imaginary reality becomes more real by making models of these senses electronically and mechanistically, while making feedback to viewers at real time.

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Chapter 3. Influence of Images and Others on the Human Body

In this chapter, the result of examination condition on the effects of images and others on human body will be introduced.
The chapter first outlines the study group set up by Ministry of Health and Welfare that has investigated the medical aspects of the cases in the "Pocket Monster" incident, which gave the opportunity to organize the study group in the first place.. The detailed examinations of the incident done by the both groups are closely connected. Discussions were actually implemented jointly with the participation of the secretariats as observers in both of the study groups.
In the second half of this chapter, previous medical research results, which are assumed to be closely related to the incident, will be briefly introduced.
Besides the effect of existing images on human body, the effect of new image displays that are expected to be developed on human visual function, differences in effect in the growing steps of human being, effect of sound on auditory function are also briefly introduced.

1. Outline of Results of Ministry of Health and Welfare Study Group

(1) Outline of Ministry of Health and Welfare Study Group

The pocket monster incident was also taken up by the study group (leader: Toshio Yamauchi, Professor at Saitama Medical School) as a special research project by Ministry of Health and Welfare "Clinical Research on Photosensitivity Epilepsy" from December 1997. The study group mainly investigated individual cases that received treatment at hospitals after watching the program of "Pocket Monster" in question. The group published a flash of the report on April 3rd and the final report on June 25th.

(2) Outline of the Results Reported by the Study Group

The study group was divided into three groups: field study group, case study group, and fundamental study group. These three groups clarified the following so far.

From the findings obtained by each of the three groups, health damage (including seizure) occurred to persons under 20 of age who watched the program in question can be summarized as follows.

1) It is estimated that approximately 10 % of the viewers who watched the program suffered from health damage.

2) Symptoms that were heard most frequently were 'eye pain', 'feeling sick', 'blurred', and 'nausea', namely symptoms of eye/visual sense, sickness, head, or stomach, though there were a few percentage of the patients who suffered from convulsions.

3) Among those who went to the hospitals, 80% of them suffered from seizures. Among those who suffered from seizures, 66.3% of them showed convulsions. The rest of the patients complained headache, vomiting, or symptoms of unidentified complaint.

4) Among those who suffered from seizures, persons who had diagnosed as epilepsy or those who were taking antiepileptic drugs consisted 30%. Among those who were taking the drugs, there were cases who showed only visual seizures or disturbance of consciousness, but not convulsionary seizures.

5) Among those who went to the hospitals, half of them had never experienced seizures. Among these, 77.3% experienced convulsions.

6) Among those who went to the hospitals, approximately 50% showed some kind of abnormality in the brain wave. Among those who had never showed paroxysmal symptoms, 37.5% had some kind of abnormality in their brain wave.

7) Among those who went to the hospitals and were able to have a brain wave test, 60% or more had sudden abnormal brain wave in the light activation brain wave, namely sudden light reaction. Even those who had no experience of seizure, 65.6% of them showed sudden light reaction.

8) Among those who went to the hospitals, 1/4 of them had no abnormality both in general brain wave and light activation brain wave. Among them, symptoms of autonomic nerve system, vomiting, unidentified complaint were seen most frequently. It is estimated that these cases take up most of the health damages seen at the incident.

9) The image that caused health damages was of 12 Hz and of a combined flashing light of red and blue. Generally it is thought that stimuli of 10 Hz or more and of a combined flashing light of red and blue has a high risk of inducing health damages.

10) It was estimated that watching television close to the set in a dark room can also reinforce health damages.

Possible Diseases from the Result of Symptoms Examination
From the diagnosis and examination of brain wave from the perspective of clinical neurophisiology, following groups among those who suffered from health damages were drawn.
Type #1: Disease that occurs epilepsy or seizure similar to epilepsy. In this sense, it can be understood as photosensitive epilepsy that occurs photosensitive seizures.
Type #2: Cases that do not show any abnormality in a general brain wave, but shows sudden photo paroxysmal reaction (PPR) triggered by light stimuli. It is the original type of photosensitive epilepsy. Can be seen most frequently in infanthood and adolescence and therefore, age-depending. It is seen among female. Symptoms are general convulsionary seizures.
Type #3: Cases show no disorder either in a general brain wave and in case of receiving a light stimuli. Symptoms as nausea, headache, sickness of unknown causes were seen most frequently. One of the possible factors of this type would be estimated that autonomic nerve system was extremely stimulated induced by visual stimuli and is related to psychological and other factors similar to motion sickness.
Possible measures are as follows.
1) In case of experiencing voluntary seizures without any particular inducement, or repeated symptoms of seizures without any light stimuli as television, it is suggested to have diagnosis, especially brain wave test at the hospital.
a) In case that a disorder is seen in the general brain wave and also sudden wave is induced by light stimuli, diagnosis and guidance for avoiding input of light stimuli like television must be conducted.

b) In case no disorder is seen in the general brain wave but sudden abnormal wave is seen induced only by light stimuli, input of strong light stimuli must be avoided. In this case, possibility of light-induced seizures to occur will be likely to decrease along with age.

c) Above cases of brain wave disorder is small in number as a whole. Most of the cases are symptoms of autonomic nerve system or visual function and therefore, for general viewers, it is favorable to watch television at least 1 meter away from the set and in a bright room.

2) For example, it is favorable to avoid high risk of visual stimuli as of red and blue flashing and relatively high frequency which induce symptoms, and in case of using any optical instrument as well as television, the above must be considered sufficiently.

2. Previous Medical Research Results (Survey of Literature)

(1) What is Photosensitivity?

Photosensitivity is the state in which epilepsy waves are seen in electroencephalogram by visual stimulation such as light. Some cases are accompanied by photosensitive seizures while others show only epilepsy waves in the electroencephalogram with no seizures throughout life. Most cases show factor normality and age dependency.
Epilepsy, on the other hand, means chronic cerebral disease with repetitive seizures generally with no cause. One specific type of epilepsy is photosensitive epilepsy (PSE). PSE seizures are induced by light (visual) stimulation. Types include PSE where seizures are induced only by light stimulation and PSE accompanied by voluntary seizures not induced by light stimulation.

(Major Advances in the History of PSE)

1946: Walter reports that seizure waves are induced in electroencephalogram by flashes.
1952: Bickford classifies optical seizure reaction indicating photosensitivity of the central nervous system from light myoclonus reaction induced in electromyogram of the orbicular muscle of eye.
1952: Livingston reports TV epilepsy for the first time.
1981: Rushton reports space invader epilepsy for the first time.
1989: Maeda et al. of Japan reports video game epilepsy.
1992: Waltz et al. reports four types of sudden optical reactions indicating photosensitivity of the central nervous system. The four types of sudden reactions are:
Type 1: Spike in the occipital region matching with the flash
Type 2: Spike predominant in the occipital region
Type 3: Spikes and waves spreading to the front region, predominant in the occipital region
Type 4: Spike and wave complex (matches with light epilepsy reaction. Some have commented that only those cases should be called photosensitivity.)

(2) Visual Stimulation Causing Photosensitivity

Physical properties of visual stimulation

1) Flashing light stimulation

a) Frequency
Activator actions are great at 10 to 30 Hz (actions causing reactions in the brain by stimulation or size of reaction occurred) (Kasteleijn-Nolst Trenite 1989, Harding et al. 1994). Particularly large at 15 to 18 Hz (Binnie et al. September 1992).
Easily activated when below 20 Hz with eyes open and above 20 Hz with eyes closed (Harding et al. 1994)
Small children are easily activated below 10 Hz, while those in their teens and above are easily activated above 10 Hz (Laget et al. 1954).

b) Color
Many have reported that red flashes have greater activator effects than white flashes (Carterette et al. 1952, Takahashi 1976, Harding et al. 1994).
Blue has slight activator effects (Takahashi 1976, Harding et al. 1994).
Many have also reported that activator effects are greater with the eyes closed than open (Bickford et al. 1953, 1969, Kooi 1971, Panayiotopoulos 1974).
There are also some theories that the eyelid acts as a red filter.

2) Stimulation of flashing patterns

a) Patterns
Dense and simple patterns (stripes, spots, checks, vortices) have greater activator effects (Hickford & Klass 1962, Klass et al. 1976), especially for check patterns (Wilkins et al. 1979). Vertical stripes are stronger than diagonal stripes (Bickford & Klass 1962).

b) Contrast
The intensity of the contrast is proportional to its activator effect (Wilkins et al. 1979).

c) Position
Activator effects of patterns are stronger at the center of the screen.

d) Size
The activator effects increase in linear proportion to the intensity of the stimulus in the range up to 48 degrees of vision (Wilkins 1989, Kasteleijn-Nolst Trenite 1989, Binnie et al. 1992).

e) Spatial frequency
For striped and checked patterns, patterns with a figure to ground ratio of 1 to 1 and in the range of 2 to 4 Hz in respect to 1”Eptical angle have strong activator effects (Wilkins et al. 1979, 1989).

f) Relation with photosensitivity
Among the cases that shows sensitivity to flash, 30% were found to be sensitive to still stripe patterns and 70% to reverse stripe patterns (Wilkins et al. 1980). Excluding cases with cerebral disorders, there are very few cases showing only sensitivity to patterns without sensitivity to flashes (Binnie et al. 1992, Brinciotti et al. 1994).

Visual stimulus by TV
1) TV images have low luminance compared to flashes of strobes (while the strobe of current electroencephalography tests is 4000 to 5000 cd/m2, the average brightness of the TV screen is 20 cd/m2). According to a research on light stimulation by the same luminance as TV images (Takahashi et al. 1995), light stimulation with the greatest effects are: 20 cd/m2 red flashing (15 Hz), 2 cycles/degree blinking of geometric patterns (20 Hz).

2) Stimulation by flickering of patterns on TV
According to ITC guidelines, assuming that a normal 25-inch TV is viewed from 2 m away, stripe patterns that are 0.4 to 2 cm wide (if the whole screen is striped, 10 to 40 stripes = 1 to 5 cycles/degree) should be avoided.

3) Flickering of TV screen itself
This occurs easily when a TV is viewed from 1 to 2 m away in a dark room (Wilkins 1979, Binnie 1992). This occurs mainly in Europe where the frequency is 50 Hz and less in North America where the frequency is 60 Hz (Quirk et al. 1995). Viewers are expected to be more than 2 m away from the TV, brighten the room, or place a table lamp on the TV. In a case of moving towards the TV, covering one eye with a hand can prevent triggering effects (Harding et al. 1994).

4) Flickering of interlaced scanning lines
Induced easily when watching the TV close up in a bright room (Wilkins 1979, Binnie 1992). In such a case, moving away from the TV can reduce the risk, or if the stripes cannot be distinguished because of the small screen, visual stimulation would be less. When a viewer must get closer to the TV screen, covering one eye with a hand can be effective (Harding et al. 1994).

Effects of opening and closing the eye on visual stimulation
1) Single-eye stimulation and both-eye stimulation
Compared to single-eye stimulation, both-eye stimulation has several times stronger activator effects (Wilkins et al. 1979, Binnie et al. 1992).

2) Opening/closing eyes
In cases with photosensitivity, seizure waves may be induced by closing the eyes. This is found common in elderly cases with cerebral disorders (Takahashi 1976). Seizures are induced easily under bright lights when the eyes are closed, and are difficult to induce in dark surroundings (Harding et al. 1994).

3) Movement of eyeballs
In cases with photosensitivity, seizure waves are induced by the voluntary displacement of the eyeballs, and this is found commonly amongst elderly cases with cerebral disorders (Takahashi 1976).

(3) Occurrence of Photosensitivity in the General Population

1) The frequency of photosensitivity in healthy patients is thought to differ due to the difference between the definition of photosensitivity (narrow definition of light cramp reaction, or broad definition of sudden light reaction, or occasional reports on slow wave clusters), and optical stimulation method (stimulation by flashing, stimulation by patterns, or other physical means).

2) The frequency is high starting from late infancy to early adolescence (Jeavons et al. 1982, Kasteleijn-Nolst Trenite 1989, Doose et al. 1993) and shows its peak at the ages of 12 to 14 (Binnie et al. 1992).

3) The average age where photosensitivity disappears is in the 20's (Kasteleijn-Nolst Trenite 1989, Harding et al. 1994). However, it is found to continue over a long period of time into adulthood in cases of negative hereditary factors being clear(Doose et al. 1987, 1993, Harding et al. 1994).

4) Frequency is high in females (Doose et al. 1973, Eeg-oloffson et al. 1971, Wilkins 1980, Kasteleijn-Nolst Trenite 1989, Waltz et al. 1992, Binnie et al. 1992, Doose et al. 1993, Quirk et al. 1995).

5) Photosensitivity is hereditary. Photosensitivity has been confirmed in 40% for siblings of cases with photosensitivity and around 16% for parents (Doose et al. 1973).

Table Frequency of Photosensitivity in Healthy Patients


Age Studied

Number of

Proportion of
persons (%)

Type of Photosensitive reaction

Herrlin (1954) 0 to 15 year-old

70 cases


Marked 2 to 5 Hz wave cluster seizures
Egg-Oloffson (1971) 1 to 15 year-old

605 cases


Overall slow wave clusters or slow wave clusters


Local spikes and waves
Brandt et al (1961) 1 to 16 year-old

120 cases


Sudden overall clusters
Dooze and Waltz (1993) 1 to 16 year-old

662 cases


Sudden optical reactions
Papatheophilon et al (1976) 12 to 16 year-old male

223 cases


Spikes and waves or multiple spike and wave clusters
Egg-Oloffson (1971) 16 to 21 year-old

185 cases


Sudden activities
Gregory et al (1993) 17 to 25 year-old

185 cases


Overalll spikes and waves
Mundy-Castle (1953) 22”Ž25 year-old

154 cases


Multiple spikes, multiple spikes and waves
Kooi et al (1960) 20 to 60 year-old

121 cases


Light epilepsy reaction
6) 7.6% of healthy persons (1 to 16 years of age) have photosensitivity. Amongst these, seizures occur at a frequency of 5% (about 0.4% of healthy persons). 3% (about 0.2% of healthy persons) of them are diagnosed with epilepsy with repetitive seizures to age 20 (Doose & Waltz 1993). For photosensitivity only, many do not show clinical symptoms (So et al. 1993). The frequency of seizures is high with cases who had had a similar case in their families in the past and cases showing spiks and waves apart from photosensitivity (Doose et al. 1973).

7) Cases with photosensitivity tend to show excessive excitability of the central nervous system, and some reports have indicated non-epileptic symptoms such as syncope, night terror, loss of appetite, vascular headache (especially migraines), etc. but there is little verification data (Gross-Selbeck 978, Doose et al. 1993).

(4) Photosensitive Epilepsy

People with photosensitive epilepsy make up a fixed percentage of those with photosensitivity.
Photosensitive epilepsy consists of pure photosensitive epilepsy and photosensitive epilepsy with voluntary seizures.
The following table indicates the seizures which tend to occur easily for each type of photosensitive epilepsy.

Type of Seizure

Pure Photosensitive

Photosensitive Epilepsy
with Voluntary Seizures

Tonoclonic seizures



Yawning seizures



Myoclonic seizures



Partial seizure






Myoclonic seizures and other seizures



(Harding & Jeavons , 1994)
Pure Photosensitive Epilepsy
1) Pure photosensitive epilepsy occurs only in the presence of photic stimulation, and sudden optical reactions are induced in the electroencephalography by flashes. This is seen commonly from late infancy to early adolescence, mainly in females (Harding et al. 1994). Self-induced attacks are also seen.

2) There are many cases of global epilepsy, most of which are tonoclonic seizures and can be seen in cases of yawning seizures and myoclonic seizures (Binnie et al. 1992, Doose et al. 1994).

3) There are rarely partial seizures of the occipital lobe in which there are simple visual symptoms, headache, upper stomach uneasiness, nausea, and cases of light impairment of consciousness and lack thereof (Guerrini et al. 1995).

4) In the cases of light induced epilepsy, pure light induced epilepsy makes up about 40% (Binnie 1992) or 3% (Takahashi 1996) of the total according to the study cited.

5) Among those called TV epilepsy, seizure that occurs only when viewing TV is considered pure photosensitive epilepsy and there are other cases of self-induced photosensitive epilepsy. There are reported cases of self-induced seizures where the patient seemed to be totally absorbed in television and seizures were triggered (Andermann 1971).

6) There are also two types of epilepsy in the video game epilepsy. One is the primary video game epilepsy which occurs only during or immediately after video games and the other is the secondary video game epilepsy which can also be self induced (Takahashi 1994). It is not clearly proven whether they are light or pattern induced. 53-56% of the younger age groups and 29% of the older age groups, are photosensitive but for the others, factors of eye movements, hand movements, intense concentration, and emotional changes are suspected (Takahashi 1994). In special cases, seizure waves are triggered only when concentrating on the game (Maeda et al. 1990).
Fatigue and lack of sleep can also be indirect contributing factors. In contrast to general photosensitive epilepsy, video game epilepsy occurs more often in boys (Takahashi 1994). Some say this is because boys play video games more often(Maeda et al. 1990), but there is no proof that playing of video games in a longer period causes health hazard (Harding 1994).
1.5 people per 100,000 experience their first seizure triggered by video games annually (Quirk et al. 1995) and 6% of regular epilepsy cases also experienced seizures during video games (Kato et al. 1994).

Photosensitive Epilepsy with Voluntary Seizures
1) Photosensitive epilepsy with voluntary seizures is not a disease but a condition found in several epilepsy syndromes. Often abnormal epilepsy waves are seen during rest, hyperpnea, and sleep. Two thirds of them are women, and many cases run in the family. It responds well to treatment with sodium valproate. In many cases, photosensitivity disappears along with age.

2) In an epidemiology study in the U.K., the annual incidence was 1.5 persons out of 100,000 persons (2% of cases diagnosed as epilepsy in the first examination) and 5.7 persons out of 100,000 persons among the 7 to 19 year-olds (10% of cases diagnosed as epilepsy in the first examination) (Quirk et al. 1995).

3) In about 80% of the cases, seizures are induced by photic stimulation in daily life, mostly by TV, followed by disco lights, and flickering sunlight (sun beams through tree shade, and on water and snow, etc.) (Binnie et al. 1992).

General epilepsy

5% (Kastelejin-Nolst Trenite 1989)

Infancy epilepsy in general

10% (Binnie et al 1992)

A. Idiopathic global epilepsy in general


    Youth myoclonus epilepsy


    Infant yawning epilepsy


    Awaking grand mal epilepsy


B. Idiopathic local epilepsy


C. Symptomatic/latent global epilepsy


    Severe myoclonus epilepsy


D. Symptomatic local epilepsy


E. Unclassifiable epilepsy


Self-induced effects
1) Self-induced seizures are seen in about one third of photosensitive epilepsies. In the beginning, it was reported that they are seen in cases with mental disabilities, but it has been found to be common amongst cases with normal intelligence (Kasteleijn-Nolst Trenite 1989, Binnie et al. 1992).

2) Self-induced seizures mainly induce yawning seizures (44% of self-induced seizures are of this type) and myoclonic seizures (33%) by closing the eyes slowly and moving the eyeballs extremely upwards. It goes unnoticed by others (Green 1966, Darby et al. 1980).

3) When under stress in a bright environment, self-induced attacks are said to increase (Darby et al. 1980, Kasteleijn-Nolst Trenite 1989). In such cases, tendensy of obsession is seen for some time, as well as resistance to regular epilepsy medication (Kasteleijn-Nolst Trenite 1989).

(5) Motion Sickness

1) Motion sickness is a type of dizziness and is also called as car sickness. It is the result of the repetition of unusual acceleration stimuli to the inner ear (labyrinth) and it is a physical illness that includes temporary cold sweat, nausea, and saliva excretion. It is caused by breakdowns in the functions of the autonomic nerves. It may be caused by bad gastrointestinal conditions, lack of sleep, and excess fatigue.

2) Symptoms similar to motion sickness can arise from realistic visual images (stimulated by virtual and moving visual images) by a visual feeling of motion which causes a contradiction between the functions of the vestibule (the balancing function of the inner ear) and the deeper perception of motion (information from the limbs and the neck) that results in a feeling of forceful motion even though the body is not actually moving. In addition to such physical stimulus input, emotional, psychological, and physical variables are thought to be the factors contributing to the condition. There are many symptoms, including eyestrain, headache, paleness of the face, sweating, dryness of the mouth, feeling of stomach expansion, muddled consciousness, impairment of directional sense, dizziness, vomiting, etc.

3) There are reports that those lower than age two are usually not liable to motion sickness, the 3-12 age range is most liable, the occurrence decreases from 12-20, and rarely occurs over 50 (Reason 1967, Reason and Brand 1975, Biocca 1992).

4) According to the research that presented moving image stimuli (mostly simple patterns) to test subjects in a broad field of vision, the following was observed:
- As the moving images became more realistic (three-dimensional images, etc.), failure of the autonomic nervous system leading to motion sickness became more common (Yano 1991).
- As the moving images became more realistic, it induced unconscious body movements which brought on motion sickness (Shimizu et al. 1991).

(6) Influence of New Images Display Techniques on Visual Function

Effect of Three-dimensional Image Display (Influence on Human Body)

1) Influence of psychological effects as 'impactfulness' or 'virtuality'
As for the psychological effects of three-dimensional image on human senses and emotions, it is reported that it is more effective than two-dimensional image in terms of 'impactfulness' and 'virtuality' as subjective evaluation.
It is experimented to quantitatively evaluate such psychological effects with physiological index. Not limited to three-dimensional images, when viewers are strongly concentrated to the image, it is said that the number of blink decrease and also when virtuality increases and viewers are deeply committed to the image, it is said that the feeling of self-movement is induced by visual senses. It is expected that research findings that help understanding such psychological effects on human body more objectively and precisely by means of quantitative evaluation experiment.

2) A person keeps standing posture by using information from visual sensory system, vestibule sensory system, and body-movement sensory system. Among these, visual sensory system contributes most to maintain the posture.
Visual stimuli forms image on the retina which induces body movement and therefore, body tilts or vibrates according to the visual stimuli, which make body unstable.

3) Uncomfortableness of Being Immersed in the VR System
Typical physiological and psychological influence caused by VR system is the comfortablenss of nausea felt when being immersed in the system. Possible diseases of this kind are simulation sickness that shows eye movement related symptoms and motion sickness that shows nausea or vomiting.

(7) Differences of Influence in terms of Growing Processes

Differences among children and adults
In terms of the influence on human body including visual sensory system, children are more likely to influenced by the image stimuli than adults depending on the degree of maturity.

1) Photosensitive Epilepsy
Concerning the photosensitive epilepsy occurs to healthy persons, the frequency is high from the late childhood to the early adolescence (Jeavons et al, 1982; Kasteleijn-Nolst Trenite, 1989; Doose et al, 1993), and highest between 12 and 14 years of age (Binnie at al, 1992).
As for the limited cases of Animation seizures, its frequency is high between 7 and 19 years of age, although low under the age of 7 and over 19, and the average age of showing the first seizure was 13.7 years old.
The reason why photosensitive epilepsy is seen in the low age group is that the threshold of convulsion related to the hereditary determinants is the lowest in the in this low age group.

2) Motion sickness
As for age, motion sickness is not likely to occur at the age of 2 or younger, occurs most from 2 to 12 years of age, decreases from 12 to 21, and becomes rare over 50 years old (Biocca, 1992).

3) Information processing system
Information processing mechanism of human being consists of receiving stimuli from outside environment through sensory organs, transferring to brain in perceivable forms of information, processing them at the central nervous system, and expressing the output as reaction and behavior.
There is some limitation in the information processing ability and it is impossible to process all of the huge amount of information. Therefore, most of the information is disposed and only a part of it is selected and is put through the higher processing steps.
The concept of capacity model, as capacity meaning attention as processing resource, is very important for the information processing (Kahneman D., 1973) In this model, attention is characterized as source of psychological energy needed to execute various kinds of information processing, rather than as one of the control processes for selection of information input. However, there is some limitation for the amount of resource that can be allocated, which becomes constraint to the efficiency and the speed of possible information processing. (Takano, Noda, 1993) Therefore, it is possible to deal with or conduct several problems or behaviors at a time when such information processing itself does not need any attention resource and is customized, but not so when it is not customized.
In this sense, children are not yet good at the allocation of processing resources as opposed to adults. Especially, children stare for longer time at a visual stimulus that draws their attention strongly, as their information processing focus its resources only on analyzing the sensory input.

4) Development of brain
As is said for the development of brain which is the center of the reaction mechanism to the external stimuli;" unit generation repeats its system generation", "human brain is physiologically immature at birth", human being is born when the functions of spinal cord and brain stem are almost completely formed and most of the function of cerebrum develops after birth. Also the mylin formation of nerve fiber of frontal lobe and limbic system complete after the adolescence. Therefore, the differences of influence between children and adults were thus proved.
The frontal lobe is the "well living" part of brain which is related to the functions of feeling, will and thinking, which controls the "skillfully living" part of brain which receives and deals with the subtle changes of external world as well as satisfying the "robust" part of brain of limbic system, the oldest organ of the brain, that is related to instinct and emotion.

5) Television literacy
As various media as television, radio, video and personal computer compositely develop in the multimedia society, the ability to communicate and make use of these media is becoming necessary. The knowledge about reading and understanding the expression techniques of such media is called literacy. For example, there are people who cannot understand the relationship between two different images when a transfer occurred from one image to another. As the media develops, people who expresses uses various kinds of means and therefore, the receivers need some kind of ability to fix the distortion of their perception. Particularly for children, it is said that their literacy takes steps for development (G. Salomom and is pointed out that they need such ability to fix the perception distortion.
Factors in question are "cut effect" (where a scene is suddenly transformed to a different scene), "pan effect" (where a scene is panned from one side to another), "zoom" (where an image is gradually magnified), "montage" (where a several scenes are shown to make the viewer consider about the time), amongst others.

(8) Effects of Sound on Auditory Function

There has not been much progress in the research on the effect of sound to human body. The past research conducted was related to so-called "low frequency defect" which was concerning sound of frequency between a few Hz and 50 Hz, while sound comes from the television speaker is of 100 Hz to 20,000 Hz. Therefore, the possibility that a television causes low frequency defect is said to be low.
Previous research on the effect of sound, except for the low frequency ,to human body is very rare and that it is important that there will be an accumulation of results from scientific research on the matter.

References: Results of research on the effect of sound to auditory senses
1) Effect of rhythmical sound stimuli to human body
According to Hirai (1984), at the research on the effect of sound, with different hitting frequency per minute and pitch, to cerebrum and cornu ammonis of rabbits without anesthesia, it was found that the sound with low frequency (120/min) and low pitch (500 Hz) restrained perception and conscious activity, while that of high frequency (450/min) and high pitch (1,000 Hz) had an opposite effect.

2) Effect of noise to human body
According to Yoshida (1982), noise has bad influence on circulatory system (vasoconstriction, rise of blood pressure, and change of the blood constituents), digestive system (frequency of stomach constriction or decrease of secretion of saliva), endocrine (pituitary gland-adrenarline secretion), pregnancy/birth (low birth rate), sleep (late hypnosis and early arousal), performance (psychological effect), as well as causing noise induced hearing loss.
Also, according to Honma (1984), it was found by the brain wave test that the stress caused by noise lowered the attention maintaining function.

3) Stimuli induction of rats' epilepsy
According to Noda et al (1997), rats that voluntarily showed tonoclonic seizures every 30 hours were found in the Wister rat colony. The pattern of seizure and the brain wave of those rats, named as Noda epilepsy rats, were similar to the general tonoclonic seizures of human being. Also when conducting a priming with sound, 100% of them showed the above seizures. Then the various kinds of antiepilepsy drugs were tested on these rats. Also electrical and physiological symptoms of the cone cell of the cornu ammonis slice of rats that did not show any seizure were examined and it was estimated that an abnormality of the calcium channel has some kind of relationship with seizures.

to contents

Chapter 4. Methods of Image Display

This chapter discusses the appropriate methods of image display. At first it reviews how this issue in television broadcasting is being addressed by other countries, and then summarizes the views of this study group on the appropriate image display methods based upon the discussion of the medical effects of images on human visual and auditory functions.

1. Regulations Employed Abroad

According to the study by the Ministry of Posts and Telecommunications, only the United Kingdom has established regulations on the auditory and visual functions of television images. The case of the United Kingdom is described below.

(1) Background

Background of establishment of the ITC codes
In April 1993, the Independent Television Commission (ITC) gave a mandate to set up program codes and guidelines for commercials and TV programs. It was shortly after the incident occurred, which became the trigger for ITC to set up guidelines, that the people who watched the Golden Wonder Co.'s instant noodle commercial complained of discomfort. This commercial used rapidly-changing black and white patterns in the background which eventually covered the entire screen and was created by computer graphics.
As a result of this commercial, three viewers reported seizures and 25 complained of discomfort to the ITC.
Following talks between ITC, the broadcaster, and the advertising agency, the broadcasting of this commercial was discontinued.

Guidance Formation
In setting up the guidance, the ITC requested Professor Harding of the University of Aston, who is the leading figure in the study of PSE (photosensitive epilepsy), to research this incident.
Professor Harding conducted tests on PSE on over 700 patients who exhibited symptoms and compiled a draft of the guidance.

(2) ITC program codes and guidance

ITC program code (7. 3)
- Regulations on the use of blinking images and repetitive patterns
Certain uses of blinking light, intermittent light, and repetitive visual patterns may cause problems in those who exhibit PSE symptoms. The ITC guidelines are available on request.

ITC guidance

  1. Flickering or intermittent lights and certain types of repetitive visual patterns can cause problems for some viewers who have photosensitive epilepsy. The television companies, together with the ITC, have consulted with leading medical opinion in this area, to draw up guidelines aimed at reducing the risk of exposure to potentially harmful stimuli.
  2. Television is by nature a flickering medium (because of the 50 Hz refresh rate of typical receivers and the 25 Hz effects of interlaced scanning) and it is therefore not possible completely to eliminate the risk of television causing convulsions in viewers with photosensitive epilepsy, but steps can be taken to reduce unnecessary risks. The advertising and promotions, and more generally in programmes where this is practicable.
  3. Flashing lights or rapidly changing or flickering images which change at a rate of more than 3 Hz should be avoided. In marginal cases such images should be avoided if they are positioned near the centre of the screen or if they occupy more than around 10% of the picture area, or if they change substantially in brightness. Changes in colour only are not a problem.
  4. Prominent and regular patterns which cover a large proportion of the picture area should also be avoided, especially if they represent bars, spirals, or 'dartboard' patterns. Moving or flickering regular patterns are particularly hazardous.
  5. Care needs to be taken also with computer generated images, which if highly detailed, can cause a high degree of 25 Hz inter-line flicker in the displayed television picture.

Reference: 1990 Broadcasting Law (Excerpts)
Article 7. (1) The commission must establish standards on the following matters that must be reviewed as necessary, and must do everything within the powers of the commission to ensure compliance with these standards.
(a) and (b) (omitted)
(c) Other articles related to the standards and implementation methods for programs which the commission deems necessary to include within the standards

(3) Basis for the ITC guidance

Reasoning for choosing 3 Hz as a standard
- Professor Harding considered the issue upon the request of the ITC and drafted the guidance.
*Clinical tests using strobe light were conducted on over 700 cases of the PSE symptoms to determine which stimuli they were sensitive to. The tests measured their brain waves while showing images 2.5 m away from the TV screen under ordinary lighting. The test results for the 170 cases where the extent of the sensitivity was accurately confirmed were as follows:
- The only way to completely avoid photosensitive reactions is by refraining from the viewing of television.
- Upon the basis of experimental data, the ITC recommended a maximum flash rate of 3 Hz in order to minimize the risk of photosensitive reactions.
- According to Professor Harding, British TV uses 50 Hz and PSE patients are likely to be more sensitive than those in Japan, as Japanese TV using 60 Hz.

(4) Nature of ITC guidance and Review System

Nature of ITC guidance

a) Based on Article 7 of the 1990 Broadcasting Law, the ITC has the authority to establish standards, implementation methods, and any other items for programs which the commission deems necessary to be included in the standards.

b) In ITC program code 7.3, regulations were established for blinking images and repetitive patterns and details were clearly specified in the guidance.

c) The regulations in the ITC guidance are to be treated in the same way as the program codes.
- In cases of violation of the code and guidance by a broadcaster, the ITC shall notify the broadcaster of the fact. If corrections are not made, the ITC will issue an official warning. If the matter is still not rectified, fines shall be levied. As the final step, if all of the above fail, the broadcasting license (Article 41 of the 1990 Broadcasting Law and others) will be revocable.

The examination process in the United Kingdom
- The broadcasting of advertising requires an examination by the Broadcast Advertising Clearance Center (an industry organization), but there have been cases that advertisement broadcasting has not met the code standards.
Professor Harding has reviewed and modified 500 videotapes to determine if they met code standards.

(5) Recent trends

- Images not covered by the ITC codes
It has become clear after the establishment of the ITC codes that while black and white patterns flowing in a single direction are not harmful to viewers, those that have reversing patterns or stationary patterns are said to cause more problems.
It has been pointed out that a deep-red color is also harmful to human body..

(6) BBC standards

The British Broadcasting Corporation (BBC) has also implemented guidelines based on the research results of Professor Harding.

2. Image Display Techniques

The following presents the issues concerning the image display methods raised in the study group organized as the "Pocket Monster" incident being a trigger.

(1) Standards

Need for setting standards
Since the "Pocket Monster" incident was caused by the image display techniques in ways that were previously unexpected, the setting of certain standards is not only effective for avoiding similar problems in the future, but also important in giving worldwide assurance concerning the safety of techniques used in Japanese image products.

Governing entity
Standards can be issued either by the broadcasters or by the government. It is possible that the government administratively set standards, however, since the problems concerning broadcast programs are closely related to the content of expression through the methods of display, it is preferable that the broadcasters themselves carry out the process. This includes setting basic outline, establishing proper standards, and enforcing them voluntarily. They must contribute to the prevention of any serious damage such as the "Pocket Monster" incident. In this sense, the important role of the government will be to give basic directions to broadcasters and other related organizations from a broader perspective.

Numerical standards
Setting some kind of numerical standards such as those employed in the United Kingdom may be reasonable both for the viewers and the broadcasters.
However, it is important to carefully consider the following relevant matters concerning the "Pocket Monster" incident:
- Story line, viewing environment and other factors are involved and make the problem more complex.
- Conditions may differ between a case of viewing the program with prior knowledge of the content and a case of viewing without any prior knowledge.
- As Professor Harding pointed out, since television expresses images with blinking light, the only way to completely avoid the problem is to refrain from watching television. In other words, it is not possible to set standards which will eliminate all the problems.
- PSE is not the only factor that trigger the problem.
- It should be noted that the numerical standards have a inherent nature to keep being segmented.

Considering the above points, compliance of the standards alone cannot solve all the problems, even though they must be established.
What should be taken into consideration is that, for example, a favorable viewing environment should be assured, that the viewers should be informed beforehand what types of images are being used, and that problems will occur even if numerical standards are followed.

The British standards

1) Evaluation of the standards
As stated above, the United Kingdom is currently the only country to have set standards for television image display methods. The British standards were set for commercial films in the beginning, as triggered by the commercial incident, but since they were also based on the results of Professor Harding's test data, Japanese specialists in the field also consider them to be valid.

2) Evaluation of standards other than those for flashing lights
The issue was mainly about the flashing lights at the "Pocket Monster" incident, but the British standards also contain regulations for non-blinking stimuli other than flashing lights (recurring patterns such as striped patterns, vortices, concentric circles, etc.).
Japanese medical specialists have stated that non-blinking stimuli can also cause seizures. Some consider that the current incident was caused by a combination of blinking and non-blinking stimuli.

3) Measures for the red color
Neither of the current British standards of ITC nor that of BBC cover the use of the deep red color. Whether this should be referred to in the standards is currently under discussion and it is recognized as an issue that requires further consideration.

(2) Other considerations

Relationship with freedom of expression
Display methods involve issues such as the safety of images but are also closely related to freedom of expression. Upon setting any kind of standard, it is essential to pay special attention to its relationship with freedom of expression.
The continual pursuit of various display methods is an indispensable part of artistic creativity. The standards must be written so as not to stifle the creativity of producers. The producers must , however, also fully consider the effects of the display methods on the human auditory and visual functions when producing programs.

Relationship with the story line
Aside from the stimuli of blinking flashes, one of the causes of the "Pocket Monster" incident was that the content of the story was very absorbing. On the other hand, Professor Harding conducted tests with six non-Japanese speaking PSE patients by intermittently showing them the scenes in question of the story #38 of "Pocket Monster". He presented them both in color and monochrome and examined their brain waves. The result was that five of the patients showed PSE responses to the color version while none reacted to the monochrome version. Thus, some members of the study group strongly believed that the story content is totally irrelevant and is only one of the factors that encourages excessive fixation on the screen and that the real causes are the blinking and non-blinking stimuli.
The issue of the story line is closely related to the freedom of expression as stated in a), so it is not proper at this time to give directions on the issue as there is no professional consensus on the matter. Further study should be required.

Ensuring compliance of the standards
The issue of ensuring compliance to the standards will depend on whether they are imposed by government or industry and also on the nature of the standards. If self-regulation by broadcasters is desirable as previously stated, it is preferable to set up a system where voluntary compliance can be obtained.

Publicizing warnings
Following this incident, some broadcasters are giving warnings to viewers prior to broadcasting. Some members of the study group pointed out that these warnings are well received by viewers so far.

Viewing environment
The suggestions made by Professor Harding were; "to watch television in a brightly lit room", and "to be more than 2 meters away from the screen". They are remarkable suggestions that require further research, for any consensus on this matter has not been reached by the medical specialists.

3. Differences of Image Display Techniques depending upon the Broadcasting Methods

(1) Images Willingly Demanded by Viewers

There is a point of view that there should be differences in the image display method between pay programs and those free of charge that viewers are exposed to against their will. In other words, it is a question of whether we can treat equally the former, namely programs assuming that the viewers would willingly watch, and the latter, which are fed into our eyes whenever turn on TV regardless of our will.

Differences between nonscramble programs and scramble programs from the viewers' point of view

There are following differences between nonscramble programs and scramble programs in terms of the access from the viewers.

Nonscramble Programs

Scramble Programs

Ways of Access

100% of the households nationwide own television receiver and anyone can watch (NHK and commercials)

Programs that viewers are able to watch by payment

There are three kinds of scramble programs; Generally, the viewers select programs that they wish to watch depending upon the content and not on what kind of image display is adopted.
Therefore, even for the scramble programs, viewers are not aware of the image display method adopted to the program until the moment they watch it. Nevertheless, when the image display method is announced to the viewers in advance of broadcast, they would be able to avoid programs that are not suitable to them.
In addition, even for free animation programs, there are some programs that display caution about the viewing environment when viewers (especially children) are to be exposed to them, so that the viewers can be properly informed in advance and take the caution into consideration.

(2) Programs Suitable for Adults and Those for Children

As referred in chapter 3 at (7), there were reports from various aspects that frequency of photosensitive epilepsy and motion sickness of children is higher than that of adults, children are more likely to stare at visual stimuli that draw their attention at visual information processing, maturation of brain completes during the period of youth, and children are at their developing stage in terms of their literacy of television expression method, which can be concluded that children are more likely to be affected by images than adults.
Therefore, concerning the above, the following considerations must be taken by broadcasters and viewers.

1) For broadcasters

a) Broadcasters take sufficient care for the image display of programs whose viewers are mainly children

b) Broadcasters take sufficient care for the image display of programs (including commercials) during the time when viewers are mainly children.

c) Broadcasters inform viewers of favorable viewing environment of programs that children take up the most part of viewers.

2) For viewers

a) Parents take responsibility to give favorable viewing environment to their children, for children cannot be responsible for themselves in this respect.

b) Viewers secure favorable viewing environment for their own.

c) Be aware of caution displayed in advance of programs.

d) Parents make sure that their children understand the content and the meaning of the caution displayed in advance of programs.

(3) Image Displays for Commercials and Those for Ordinary Programs

Effects of commercial images
Very impactful images and image effects are tend to be used for commercial images in order to draw attention of the viewers. Actually, the establishment of ITC code in England was triggered by the PSE seizure incident, whose cause was a commercial image.
It is not yet clear to what extent the image effects as referred in chapter 2 are used in commercial and what percentage they cover compared to general programs, however, conditions in which images of strong impact are used for commercials compared to other general programs are thought to be as follows;

Commercial images

General program images

Viewers' attention drawn and its continuation Commercial image has its aim to draw attention of viewers in the full time of 15 or 30 seconds, for the limitation of broadcast time. Therefore, impactful images and image display, and changing images method that give high density visual information are used. In terms of general program images, the degree of viewers' attention to be kept drawn is not so high as compared to the case of commercial images. Generally it is drawn by the program content rather than the impactfulness of stimuli.
Viewing frequency As commercial images are repeatedly broadcast and their schedule to be on the air is not fixed, viewers frequency of watching them becomes high. Schedule of ordinary programs is set and viewers select what they would like to watch.

Examination Process of Commercial Images
Following is the review of the examination process of impactful images that are likely to be adopted to commercials until their broadcast.
1) Abiding regulation for commercial images
Under the broadcast law, regulations are applied to commercials just as they are to general programs. In addition, it is required to abide by other legal regulations and voluntary regulations for commercial in general.
However, these regulations are of commercial content and there are no regulating item that focuses on the display method except for subliminal technique.

2) Examination System
Commercial images are examined regarding that the above regulations are violated or not. Measures of examination consist of the examination conducted before broadcast and the one which is a grievance process conducted after the broadcast.
Pre-broadcast examination is executed at each channel. At first sales department conducts examination and a department which is in charge of examination conduct further evaluation on some of the commercials just as general programs are examined. Items examined include protecting and promoting the customers' interest, as well as violation of the above regulations, voluntary regulation criteria.
In case of a commercial that is difficult to be judged in terms of violating the regulations and whether it should be broadcast or not, the Program Criteria Examination Committee of the National Association of Commercial Broadcaster may discuss the matter and submit opinions for reference.
Also individual examinations are conducted by each commercial producers and advertisers mainly from the aspect of Unfair Competition Prevention Law.
On the other hand, in case that complaints come from customers against commercials, Japan Advertisement Screening Organization (JARO) executes examination. However, the complaint is related to the program criteria, each department (customer center, for instance) takes charge in addressing the problem.

3) Examination Department inside Broadcaster
Examination department of each broadcaster consists of 10 members in average, taking charge in examining commercials and many other programs (number of programs has increased as 24-hour-channels have spread).

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Chapter 5. Favorable Environment for Viewing

In this chapter we will discuss favorable viewing environment. Firstly, we will refer to the actual conditions of how children watch programs, followed by the results of research done by the Ministry of Health and Welfare on the relationship between the "Pocket Monster" incident and the health damages and viewing environment. Secondly, we will summarize the information related to favorable viewing environment by introducing the suggestions drawn from the incident, recommended ways up to now, and checking condition regarding the quality of television image evaluation for reference.

(1) Results from the Research "Clinical Research on Photosensitive Epilepsy" Conducted by the Ministry of Health and Welfare

From the results of the research on the health damages and the causes of symptoms occurred during the broadcast of Pocket Monster animation at 6:30 p.m. on December 16th, 1997, we selected those that are related to viewing environment.

Results of the questionnaire survey on students of elementary schools, junior high schools and high schools
Among the 9,209 valid samples, 4,026 (43.7%) of them were watching the story of Pocket Monster in question and those who suffered from health damage were 417 persons which consist 10.4% of those who were watching the program. Health damage as defined here means convulsive seizure, eye pain, feeling sick, blurred, nausea, was not able to avert eyes from the screen, blinking hard, etc.

1) Brightness of Room and the Conditions of Health Damage Occurrence
a) Conditions of Health Damage Occurrence

Brightness of Room


Persons Suffered
from Health Damage

Percentage of Health
Damage Occurrence

Watched in a bright room




Watched in a dark room




b) The occurrence of health damage was significant in case of watching in a dark room.

c) Frequency of occurrence of most of the symptoms was higher for samples who watched in a dark room and they experienced "legs shaking, fitting, and convulsion" in particularly high frequency.

Distance from Television Set and the Conditions of Health Damage Occurrence
1) Conditions of Health Damage Occurrence

Distance from Television Set


Persons Suffered
from Health Damage

Percentage of Health
Damage Occurrence

1 meter of closer




1 - 2 meters




2 - 3 meters




3 meters or further




b) Considerable number of health damage which is statistically significant occurred to the viewers who were watching within 1 meter.

c) Frequency of most of the symptoms tended to be high for those who watched 1 meter or closer to the set, however, "eye pain" and "feeling sick" occurred unrelated to the distance.

d) For those who watched in a bright room, health damage tended to decrease (statistically significant), however, it was not made clear whether the health damage decreased depending upon differences in distance for those who watched in a dark room. (For those who watched in a dark room, there were considerable number of health damages unrelated to the distance.)

Relationship with Viewing Conditions
a) Conditions of Health Damage Occurrence

Viewing Situation


Persons Suffered
from Health Damage

Percentage of Health
Damage Occurrence

Watched alone




Watched with someone else




b) Statistically significant health damage occurred to those who watched alone.

(2) Data on Viewing Environment

Following is the statistical data related to the viewing environment we obtained out of the results of questionnaire survey conducted for elementary schools, junior high schools, and high schools (Conducted for 11,368 persons and among them, 4,026 persons watched the story in question; described as ­” in the following) and results of diagnosis by specialists, the survey conducted by the Symptoms Examination Group (115 cases; described .

1) Distance to the Television Set

Breakdown of the 4,002 Valid Samples
1 meter or closer


1 - 2 meters


2 - 3 meters


3 meters or further


158 Valid Cases

2) Brightness of Room

Breakdown of 3,934 Valid Samples
95.5% watched in a bright room while 4.5% watched in a dark room.

Breakdown of 160 Valid Cases
96.2% watched in a bright room while 3.8 % watched in a dark room.

3) Viewing Situation

Breakdown of 4,009 Valid Samples
27% "watched alone", while 73% "watched with someone else".
Breakdown of 154 Valid Cases
84.4% "were paying all the attention to the program", while 15.6% "were doing something else while watching TV at a time".

4) Size of the Television

153 Valid Cases

(3) Suggestions for Favorable Viewing Environment

As in the following, suggestions for favorable viewing environment that take consideration particularly to photosensitive epilepsy after the Pocket Monster incident, and existing recommendations are presented. However, items may not be consistent with each other.

Suggestions that Take Consideration to Photosensitive Epilepsy

Relationship between Distance from the Television Set and Interlace Flicker
  • It is suggested that viewers should be 2 meters or further from the set in order for the interlace flicker (flicker by intermittent scanning) to be in the sight. (*1)
Distance from the Television Set
  • It is suggested that viewers should be 2 meters or further from the set when watching the television. (*1,2)
Room Light
  • It is suggested to turn on a small lamp on the television so that the difference of brightness between the room and around the set is decreased. (*1)
  • It is suggested to watch television in a bright room. (*2)
Changing Channels
  • It is suggested not to be close to the screen for changing channels. (*1)
  • It is suggested to use a remote controller to change channels, not to get closer to the screen. (*2)
Approach toward the Set
  • When viewers need to get closer to the screen, it is suggested to cover one eye with a hand in order to avoid the light. (*1)
Viewing Time
  • It is suggested not to watch television for long time. (*2)
  • It is suggested that the screen should not cover the whole sight.
  • When viewing a flickering screen, it is suggested to cover one eye with a hand.
  • When feeling something unordinary, viewers are suggested to avert eyes from the screen.
  • It is suggested to avoid lack of sleep, tiredness, and not to watch television when in a poor condition.
Note: *1: Harding, 1995
*2: Home Page of Nagoya University, School of Pediatrics (Prof. Watanabe)

Existing Suggestions that Have Been Widely Recommended to the Society
Distance from the Television Set, Size of Screen /Viewing Distance
  • 2.5 meters for 13 and 14 inch televisions and 3 meters for 19 and 20 inch televisions. (*1)
  • 4 to 6 times of the vertical length of the screen for present television sets. (*2)
  • 5 to 7 times of the vertical length of the screen. (*3)
Room Light
  • Brightness of room to be 60W (light bulb), 20 W (fluorescent) per 9.9 . (*1)
  • A little bit darker than usual brightness. (*2)
  • Brightness around the television is to be 15% of the maximum brightness of the screen. (*2)
Viewing Angle
  • Vertically 43 degrees and horizontally 57 degrees. (*2)
Height of Eyes
  • A little bit lower than the eyes. (*1,3)
Condition of Screen
  • Avoid light to come into sight. (*1)
Contrast of Screen
  • Should not be too strong. (*1)
Fixing Color
  • Images with reddish color exhaust eyes. (*1)
Viewing Time
  • Within 2 to 3 hours. 10 minute break is needed every 30 minutes to 60 minutes of viewing. (*1)
  • Eyes need to be rest sometimes. (*3)
Note: *1: Hibino, Kumiko (ed.), Study of Eye-Friendly Glasses (in Japanese)
*2: ITU (International Telegraph Union)
Recommendation ITU-R BT. 500-7 (1947-1978-1982-1990-1992-1994-1995)
"Methodology for the Subjective Assessment of the Quality of Television Pictures"
Recommendation ITC-R BT. 1127 (1994)
"Relative Quality Requirements of Television Broadcast Systems"
Recommendation ITU-R BT. 1128-1 (1994-1995)
"Subjective Assessment of Conventional Television Systems"
*3: Television Manufacturer's User's Manual

Further consideration concerning the effects of viewing environment on audio-visual function and scientifically verified concrete guidelines should be established and examined

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Chapter 6. Proposals - Prevention of Image Displays and Others that Excessively Affect the Human Visual Functions

Our study group has examined the effects of television programs on audio-visual function. Variation of expression methods should be secured in the television programs, however, it is quite serious that display methods of television program actually damaged many of the viewers' health conditions. Also, as pointed out in the report of the Ministry of Health and Welfare study group, causes of the incident can be of photosensitive epilepsy, factors of motion sickness or possibly psychological factors and therefore, reactions should be taken on the basis of results obtained by examining the relationship between the stimuli and the symptoms, including psychological factors. We propose the following for the proper use of image display on television, mainly for prevention of the cases caused by PSE.
Although we made proposals on the celluloid animation, there exist similar problems in the other television programs except for animation in terms of image display methods and therefore, we cover the methods adopted in all the programs.
As the fusion of telecommunication and broadcasting develops, there are possibilities that the cases of the secondary use of television programs or other software will increase. Therefore, in terms of the effects of image display methods on audio-visual function, an approach to the image industry as a whole, rather than broadcasting itself, is needed.

(1) Broadcasters should keep in mind the visual impact of their programs upon viewers.
They should also voluntarily formulate guidelines which are as specific as possible and based on the scientific criteria and the execution of effective application is appropriate based on the production methods and the target viewers.

(2) The guidelines should at least address the following at present.
a) Flashes of light
b) Recurring patterns
c) Use of red in images
d) Intensity (Brightness)

British standards (ITC and BBC standards) are deemed an appropriate model by specialists in Japan.

(3) When other effects of programs on audio-visual function are discovered, an examination should be immediately conducted in order to reflect them in the guidelines.

(4) Viewers should be warned beforehand about programs for which caution is advisable. To avoid the problems, it is important to ensure a good viewing environment. Therefore, broadcasters should work to educate viewers and provide them with warning about this problem in advance and viewers should also make an effort to protect themselves. To a certain extent, these efforts are already being carried out.

(5) More research is needed on the degree to which story line affects the visual impact of programs.

(6) To aid further research in this field, we should inform broadly to the international community of the results which we obtained through this research.

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Chapter 7. Issues that Need Future Discussion

In this examination, we analyzed the effects of programs on audio-visual function based mainly upon the results of bio-medical research and made proposals on how broadcasters, producers and viewers should react to the issue. However, research results have not been accumulated enough in the field and therefore, further research must be conducted regarding the effects of new image display method as three-dimensional image upon audio-visual function, the favorable viewing environment based on scientific analysis, and the mechanism of the effects of image and sound upon human body.

In order to lower the possibility of health damage of the viewers, further research and sufficient precaution are needed. Also the system that the industry, the educational institutions and the government can cross-functionally interact and collaborate should be secured. Finally, actions must be taken immediately when new facts are discovered on this issue.