If I were designing a study in which I wanted to assess memory, I might ask people to remember three words, then have them recite a phone number to prevent of the three new words

If I were designing a study in which I wanted to assess memory, I might ask people to remember three words, then have them recite a phone number to prevent rehearsal of the three new words.

Explanation:

When asked to memorize information, be it words or numbers, for instance, people tend to rehearse it mentally to remember it for a longer period of time. However, it is possible to prevent rehearsal from happening when conducting studies to assess memory. One of the ways is precisely the one described in the question. People were asked to memorize three words, but were prevented from rehearsing them by having to recite a phone number. In that case, as studies have shown, there is memory decay.