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I Think, Therefore I Jam

Even unperceived beat changes get picked up by your brain

TUESDAY, June 5, 2001 (HealthDayNews) -- Perception may not be reality after all.

In fact, claims a Connecticut researcher, the brain at times prompts you to change your actions before you even realize there's a need to change.

"Perception does not intervene between sensory input and action, at least not necessarily," says Bruno Repp, a senior scientist at Haskins Laboratory in New Haven, Conn., an independent research institute focused on the biological bases of speech and language.

Consider, he says, how people keep up with a musical beat.

In a series of five experiments, Repp asked eight people -- a mix of men and women of varied ages and musical backgrounds -- to listen to pulsing tones from a digital piano. The participants were told to tap a key on a silent piano keyboard either in sync or out of sync with the tones.

When the rhythm of the tones changed, the tappers adjusted their tapping as well -- even when the degree of change was less than 2 percent, an amount considered undetectable or below the perceptual threshold, the study says.

"The results suggest that, at some subconscious level, sensitivity to timing is very high," Repp says. "My results suggest that human sensitivity to temporal change exceeds the sensitivity suggested by psychophysical studies, in which people report whether they have heard any change." His findings appear in the June issue of the Journal of Experimental Psychology: Human Perception and Performance.

The point, Repp says, is to determine what role perception plays in all this.

"The main issue is whether perception mediates between sensory input and control of actions," Repp says. "If that were the case, temporal perturbations that are too small to be perceived consciously…should not have any effect on synchronization. However, I have shown that they do have an effect."

The brain processes this information subconsciously and then automatically uses it to control, or change, our actions, Repp says.

That's similar, he says, to what can happen with a so-called undetectable visual stimulus, as well.

"There are lots of studies in recent years, which show that a masked visual stimulus -- a printed word followed immediately by some visual pattern so that observers are quite unaware that a word was presented -- nevertheless affects reaction time," Repp says.

"There is a lot of evidence now that much sensory input is processed subconsciously and has effects on behavior," he says.

Someday, Repp says, he'd like to study what implications these findings might have on the synchronization that's necessary for ensemble musical performances.

"I am currently engaged in a long series of simple synchronization experiments, not yet using music, but slowly getting into more complex rhythmic patterns," he says. "I plan to…slowly work my way back toward more complex rhythmic materials and real music."

What To Do

For a different take on the brain and music, check out an article from the journal Nature.

Or, you might want to read previous HealthDay articles on music and others on the brain.

SOURCES: Interview with Bruno Repp, Ph.D., Dr.Phil., senior scientist, Haskins Laboratory, New Haven, Conn.; June 2001 Journal of Experimental Psychology: Human Perception and Performance
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