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Does hand clenching improve memory?

14 Jul

The claim that a hand clenching procedure may improve memory has received a lot of attention in the media.

Here is a typical description:

“Clenching your right hand may help create a stronger memory of an event or action, and clenching your left hand may help you recall the memory later, according to a new study.”

My first advice when you hear a claim about a new memory breakthrough is to look at the original research.  Google Scholar  makes that easy. The paper, “Getting a Grip on Memory: Unilateral Hand Clenching Alters Episodic Recall” can be found here.

The first thing you will notice is that many of the media reports make errors in their descriptions of the research. For example, the study is not about fist clenching but about clenching a rubber ball.

That aside, is the claim plausible? The think the answer is yes.  There is a hypothesis called the Hemispheric Encoding/Retrieval Asymmetry model  which suggests that regions in the left hemisphere of the brain are involved in storing information into long term memory while areas of right hemisphere are involved in retrieving that information. In addition, there is evidence that clenching a ball in one hand increased the activity of the brain hemisphere on the opposite side of the body.

However, plausible is not the same as true. We need to assess the quality of the evidence and this study seems flawed in a number of ways. This response to the paper does a good job of explaining some these flaws. The bottom line is that the research does not provide convincing evidence for its claim.

This does not mean that the claim is untrue? A fair statement would be that the jury is still out until more rigorous research is conducted.

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