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Computers Understanding Thought

Kevin Spencer kspencer at iti.org
Fri Nov 25 18:47:38 EST 1994

dorman at acs.bu.edu (Clark Dorman) writes:

>In article <3b4qec$7r5 at lyra.csx.cam.ac.uk> 92tad at eng.cam.ac.uk (T.A. Donaldson) writes:

>>   I have heard about an experiment in which a computer was able to pick up
>>and understand the THOUGHTS Yes or No, and also move a cursor around the
>>screen by picking up thoughts.

[stuff deleted]

>Personally, I am _extremely_ skeptical that what is happening is based upon
>brain patterns.  Because they are using scalp electrodes in most cases (where
>the equipment is even mentioned), the noise from muscles can easily swamp the
>brain waves.  If you look at scalp recording in other fields, they usually
>have to average over many operations to determine the underlying brain

The technique from Donchin's lab (in which I'm a grad student) was to
develop discriminant functions to classify single trials as to whether or
not they contained P300 ERP components.  That's how they got around the
averaging problem.

>  Most of these people are probably fooling themselves into thinking
>that they are getting brain waves, when what is really happening is that the
>subjects are learning to contract various muscles in the scalp.  Just as you
>can learn to wiggle your ears by simply practicing in front of a mirror, you
>can learn to move your other muscles. 

Such a claim could be refuted by analyzing the data post-hoc.  I'm not
familiar with the original report of the technique from this lab, but I'm
sure that a muscle-artifact argument would have been ruled out.

>I think that the systems, even if based on muscle contractions, can be very
>useful for the disabled.  A combination system, based on visual tracking, with
>cues from scalp recording, could be more useful than the systems that are
>based purely on visual tracking now. 

The reason Farwell and Donchin tried to use the P300 component for their
"mental prosthesis" project was to overcome the problem of muscle paralysis
in patients with the "locked-in" syndrome -- they could not move *any*

Kevin Spencer
Cognitive Psychophysiology Laboratory and Beckman Institute
University of Illinois at Urbana-Champaign
kspencer at p300.cpl.uiuc.edu / kspencer at psych.uiuc.edu

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