Getting a grip—literally—can boost your memory, according to a new study. Here’s how it works: If you are right-handed, clench your right fist before taking in new information that you want to remember; then clench your left fist when you want to remember it later. If you are left-handed, do the opposite. This strange trick may work because clenching your hands activates the side of the brain that handles memory. To test this idea, researchers led by Ruth Propper of Montclair State University in New Jersey studied 50 right-handed college students. The students were divided into five groups. Each participant was given a list of 36 words to remember and a small pink ball to clench. One group clenched the ball twice for 45 seconds each with their right hands before memorizing the words. Then they did the same with their left hands before writing down as many words as they could remember. Another group performed the same task but reversed the order of the fists they made. Two other groups used the same hand each time, one group using the left and the other, the right. A final group didn’t clench the ball at all but held it gently in both bands each time. The group that started with the right hand performed the best on the memory test. In doing so, they activated the left side of their brains, which helps store memory, and then clenched their left hand, activating the right side of the brain as they recalled the information. The findings suggest that some simple body movements—by temporarily changing the way the brain functions—can improve memory. The study also found that the two left hand groups, whether there was right hand clenching afterwards, demonstrated significantly poorer memory than the other three groups. This shows that it is primarily the hemisphere active at taking in information that predominantly influences memory ability. What does "it" in the first paragraph refer to?（指 Here’s how it works 中的 it。）