[From Bruce Nevin (2001.01.01 13:40 EST)]
A story in Scientific American (January 2001, pp. 24-26, "Side Splitting: jokes, ice water and magnetism can change your view of the world -- literally") looks at work of John D. Pettigrew (University of Queensland, Brisbane, Australia) that was reported in part last March in _Current Biology_ and more fully last November at a neuroscience conference in New Orleans.
Perception of reversible figures such as the Necker cube seems to be related to something called binocular rivalry. Present irreconcilable patterns in a stereoscope (e.g. present horizontal stripes to one eye vs. vertical bars to the other), and most people report seeing the left pattern, then the right, alternating every couple of seconds. Various kinds of evidence weigh against the early notion that neurons relatively close to the retinas are competing for dominance. Replacing this was the notion that conflicting pattern perceptions (configuration?) are constructed in parallel and then attention and awareness alternates between them.
Pettigrew's work supports his theory that the two perceptions are constructed in the two hemispheres of the cerebral cortex. First, they tested this by affecting the activity of one hemisphere and not the other. Ice water dripped against one eardrum causes vertigo, followed by greatly heightened activity in the opposite hemisphere. A highly focused one-tesla magnetic field trained on the parietal lobe on one side temporarily interrupts much of the neural activity in that hemisphere.
Most interesting are the effects of laughter. While ice water or magnetic interference had some effect on the alternation of the two perceptions, "a good belly laugh either obliterated the binocular rivalry phenomenon altogether -- so that subjects saw a crosshatch of both bars and stripes -- or significantly reduced whatever natural bias the individuals showed toward one of the two forms [some previously showed a bias for one, some for the other], for up to half an hour."
"'It rebalances the brain,' Pettigrew says, 'and literally creates a new state of mind.'"
There are some interesting diagnostic possibilities if preliminary indications are born out that bipolar disorder and schizophrenia are associated with abnormalities of the "binocular rivalry" alternation. Pettigrew, with bipolar disorder, found that his own brain took 10 times longer than normal to switch between bars and stripes, confirmed this with his bipolar parents, and has a clinical trial in progress. Keith White (U. Fla.) reports abnormalities with many schizophrenics -- the article doesn't specify what the abnormalities are.
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This accords well with studies of communication that suggested that people construct two kinds of interpretation, usually referred to (perhaps misleadingly) as verbal and nonverbal, and that they are normally aware of one "channel" but subconsciously respond to (and partly by means of) the other. If the two are consistent with one another ("congruent") this is not problematic, but even in a purely verbal channel like email when a person says one thing with the literal meanings of his words, for example, and expresses something inconsistent with other aspects of their meaning (ambiguities such as alternative meanings of the words and syntax, associativity of the particular word choices made, affective tone, pragmatic effects of the message, etc.) it appears that the alternative construals are built up in parallel.
This is a form of conflict in perception, not in control of perception. My hunch, based on non-experimental observation and thinking about the above issues of communication, is that when control conflict is involved, one of the alternative constructs is strongly preferred and the other is ignored (made "subconscious"). I believe that the mild preference for bars or stripes mentioned above reflects the slight or incipient control involved because the alternation is a disturbance to some reference concerning the stability of the perceived world and subjects want the alternation to settle down. It is not presented as a control task but rather as an uncontrollable normal phenomenon. Various experiments suggest themselves. For example, if the subject is asked to control the randomly disturbed orientation of the bars, the above hunch predicts a reduction in time that the stripes cycle into view. (Variants with or without the stripes being disturbed in parallel, oppositely, or independently might become interesting, depending on results.)
Ambiguity is much more prevalent than we normally realize, simply because we normally are aware of only one higher-level construal of lower-level inputs, with obvious dependency on what variables we are controlling at the higher level. The relation to mental health issues, therapy, and personal growth is obvious.
I am particularly delighted with the capacity of a good laugh to dissolve perceptual conflicts and resolve "either-or" alternations and blindsiding into "both-and" (or "neither but something like both") appreciations. And such disparities are at the root of humor. I think this has been Bruce Gregory's approach, and I salute him for it. Though obviously it would be better if we could all share the laughter.
So for the new year, and the new millennium, don't forget to laugh. (And don't forget to breathe.)
Bruce Nevin