It occurs as a monomer, G-actin, a globular protein, and in living cells as a polymer, F-actin, which resembles two strings of beads twisted around each other into thin filaments.

While the participants maintained these strings in working memory, they were given a word (e. g., shoe) and asked to respond as quickly as possible with the first word that came to mind (e. g., sock).

As a result, any sequence of strings is also e. g. a sequence of objects.