Well, I thought that it was a good question and deserved a good answer.
Plus, since I already gave a wrong answer, I feel obliged.
I already posted the results from one experiment that we tried in
class on TIPs. If you missed my posting, here it is again. The student
brought her toothbrush and alarm clock to class last Monday, plugged them
both in and demonstrated to the class that the phenomenon. WE found
1.) It was specific to the alarm clock. Other stimuli the same size etc.
did not jiggle. That ruled out the reafferent feedback explanation that I
had championed.
2.) The alarm clock did not appear to jiggle unless the toothbrush handle
was held against your chin. That ruled out the electromagnetic energy
hypothesis. (That was the explanation that my students favored.)
I think that the correct hypothesis must be that this is some sort of
apparent motion-type percept. However, that does not explain
why a post-concussion patient would not experience this. I would think
that the patient would be more likely to have damage to the vestibulo
ocular system than to systems involved soley in perception of
motion. So, the phenomenon is likely a result of both lack of reafferent
feedback and hitting some sort of apparent motion channel just right? Is
there any way to test this in class without my bringing a computer to
class and programming something?
As far as the habituation proposal goes. Wouldn't these students have
habituated by now? They're doing this at least two times a day for
years... We are moving to the memory and learning part of my class.
Perhaps they could do a little experiment on this...
As far as the 'why are students in your class brushing their teeth and
looking at TVs or Clocks' question goes... These students are living in
Manhattan. Their apartments are probably very small. For those unfamiliar
with living conditions in Manhattan. It is not outrageously uncommon for
people to have bathtubs in the kitchen. (I've known two people with
apartments like that.) So, I don't ask them why they are looking at clocks
or whatever when brushing their teeth. I don't want to know.
Thanks for all of your help. My students are really curious about this.
I'm glad to know that I am not the only one without a great answer to this
question off the top of my head. It really would be a good one for a
textbook.
Thanks,
Faith
----------------
I really like this thread, including the insight it offers us into the
private lives of other people. For example, people who brush their
teeth while watching TV. Or Don McBurney, who first reveals the
shocking truth during a discussion of after-images that he never uses
PowerPoint and now tells us that he doesn't have an electric
toothbrush either. Consequently, he misses the opportunity to observe
phenomena of great psychological importance.
Before we have further speculation on this topic, we have two
competing hypotheses to consider:
a) the perceptual hypothesis, which explains the jiggle effect
as an optical illusion generated within our own nervous system, or at
least within the nervous system of Faith's student.
b) the electromagnetic energy hypothesis, in which the phenomenon is
ascribed to physical factors external to the individual.
Two simple tests can distinguish between them. Faith, could you ask
your student to do the following, and report back to us?
1) Induce the jiggle effect by brushing her teeth. Ask other people to
report whether they also see the jiggle effect.
2) Run the electric toothbrush outside the mouth, and with no contact
between the toothbrush and its student. Does the student still
observe the jiggle?
If the answers to both 1) and 2) are yes, we have strong support for
hypothesis (b). If the answers are both no, we have support for
hypothesis a). If we get one yes and one no, we have a problem.
I'm betting on hypothesis (b).
-Stephen
Note added in proof: ok, I just ran my electric toothbrush at my
computer monitor. No jiggle, not even when it's in my mouth. This does
not seem to be a robust phenomenon. Of course, neither was cold
fusion.
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Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470
Department of Psychology fax: (819) 822-9661
Bishop's University e-mail: [EMAIL PROTECTED]
Lennoxville, QC
J1M 1Z7
Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy
Check out TIPS listserv for teachers of psychology at:
http://www.frostburg.edu/dept/psyc/southerly/tips/
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