PROBLEM: Sometimes a word is on the tip of your tongue, and it's so close a slight breeze would blow it out. But it doesn't come. Why? Maybe because you were sitting there with your hands just hanging open like a paper doll.
Making a fist with one hand has been shown to increase activity in the brain on the opposite site of your body about 90 seconds later. Right-hand clenching (which activates parts of the brain's left hemisphere) has been associated with experiencing emotions of the sort controlled by the left brain (those involved in "approach," e.g., happiness and anger). Left-hand clenching, meanwhile, is believed to bring on "withdrawal" emotions (e.g., sadness and anxiety). We also know that athletes perform better under pressure when they make a fist with their left hand. What other cognitive functions can we mess with by making fists?
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METHODOLOGY: Researchers at Montclair State University led by Ruth Propper gave memory tests to 51 right-handed individuals -- they were right-handed in that they scored of 80 or higher on the Edinburgh Handedness Inventory, which exists. The subjects had to memorize and then recall words, which they did while clenching and relaxing their hands around a tiny pink ball in specific sequences.
RESULTS: People who memorized the words immediately after clenching their right hand and then recalled them immediately after clenching their left hand did the best. They did significantly better than people who did the reverse sequence. They did slightly better than the people who made no fists at all, "though not significantly so."
IMPLICATIONS: According to prior research, left prefrontal brain regions seem to be associated with encoding memories, while right prefrontal regions retrieve them. Purposely increasing activity in those parts of the brain logically could give these functions a little boost. The effect in this small study was minimal (and contested), but it's an interesting idea. Now we just need a trick to remember which fist to make when. (Right before left -- if you're right-handed. It could be opposite that if they tested left-handed people.) If you're having trouble remembering the sequence, I'm sure there's a simple, elegant memory trick you can do with your feet.
The full study, "Getting a Grip on Memory: Unilateral Hand Clenching Alters Episodic Recall" is published in PLOS One.