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Total recall just a fist clench away

Memory aid Studying for an exam? Clench your right hand. Trying to remember a phone number? Clench your left.

That's the suggestion of a new study into the effects of fist clenching on memory.

US researchers have examined the effect of single fist clenching on memory, based on the theory that the physical action in one hand increases activity in the opposite side of the brain.

Their study, the first to test the role of different brain hemispheres in memory encoding and retrieval, is reported today in the journal PLoS One .

"We're cross-wired for body parts, so if you clench your right hand you're really causing a change in the activity of the left side of your brain and if you clench your left hand you're really causing activity to change in the right side of your brain," says lead author Associate Professor Ruth Propper, director of the Cerebral Lateralization Laboratory at Montclair State University.

"It turns out that not only do motor areas of the brain become active, which you would expect if you're moving a body part, but so do some more frontal areas of the brain also become more active when you start clenching your hand like this," says Propper.

The study showed that clenching the right fist to activate the left side of the brain just prior to absorbing information, and clenching the left fist to activate the right side of the brain just prior to recalling it, resulted in superior recall compared to the opposite or different clenching patterns.

This pattern also improved memory compared to not clenching at all, although the difference was not statistically significant, possibly due to small sample sizes, the authors suggest.

In the study, 51 solely right-handed subjects were asked to squeeze a small rubber ball as hard as possible for two sets of 45 seconds, then asked to remember or recall as many words as possible from a list of 36.

The study follows earlier research into the effects of eye movement on memory, and may tie in with the popular view that eye movements can betray when someone is lying.

"Some people have suggested that if you are telling the truth and really remembering something that happened, you would be imagining it in your head, you have a picture in your head," says Propper.

"That imaging and spatial representation is more of a right-sided hemisphere thing, and even recalling it might be a right-sided thing … so you would probably look up to your left because we're cross-wired."

However if someone was lying, they wouldn't necessarily have something to picture and may rely more on their verbal skills -- a left-hemisphere process -- so perhaps they would look up and to the right, speculates Propper.

The next step may be to investigate the same phenomenon in left-handed individuals, as evidence from eye movement studies suggests the effect is flipped in non-right-handed people.

More research is also needed to examine whether hand clenching can improve other forms of cognition, for example spatial and verbal abilities, says Propper.