Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!XEROX.COM!"chaz_heritage.WGC1RX"
From: "chaz_heritage.WGC1RX"@XEROX.COM
Newsgroups: comp.sys.atari.st
Subject: Danger from stroboscopic light
Message-ID: <890403-143813-4433@Xerox>
Date: 3 Apr 89 09:56:47 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 42

In his 24 Mar 89 22:26:10 GMT John Logajan provides a program entitled
'Alpha brain wave inducer'. Included in the program is the warning

>CAUTION: Persons susceptible to epileptic seizures should not use this!<

While in no way criticising Mr. Logajan's responsibility in having provided
this warning (many people simply wouldn't have bothered) I feel that there
may be more danger from devices of this type than is apparent.

I do not want to get involved in an argument about psychophysics. All I
know is that a cousin of mine, who was not an epileptic and had no history
of epilepsy in his family, once went to a disco where a strobe light was
being operated at what must have been a critical frequency. The result was
that he had an immediate and serious epileptic seizure and has been an
epileptic ever since.

During the 1970s the German police experimented with a riot control
equipment consisting of an infra-red 16Hz strobe light (able to penetrate
closed eyelids), referred to as a 'photic driver', and two ultrasonic
radiators producing a beat frequency of 4Hz (to deliver the necessary power
and to penetrate the skull directly, circumventing the sticking of fingers
in ears). It was estimated that within 30 seconds of switching on this
equipment in a riot situation some 5% of the people within range (esimated
at some 100m) would suffer epileptic seizures, from which a number would
never permanently recover. The equipment was never used in practice because
of the fear of litigation for damages. This project suggests that the
property, of strobes and infrasound, of inducing epilepsy in those who may
not consider themselves prone to it was sufficiently well-known, in
internal security circles at least, to justify the development costs
involved.

It may be that the strobe light (producing as it does a very brief flash)
is more likely to induce epilepsy than is the operation of this program; it
may also be that no such induced epilepsy has ever resulted from the
operation of a program such as Mr. Logajan's. However, my purpose in
posting this is simply to point out that one does not have to be an
epileptic - diagnosed or latent - in order to be at risk from flashing
lights at certain critical frequencies.

Regards,

Chaz