 The television show "MythBusters" showed that after six months of constantly rolling a stone does not grow moss.Because it is so well known, this saying is one of the most common proverbs used in psychological tests for mental illness, particularly schizophrenia, to look for difficulty with abstraction.American research conducted in the 1950s between Air Force basic airmen and hospitalized Veterans Administration patients with schizophrenia found that the way a person interprets proverbs can be used to determine abstraction ability.