While Obama used his right (nondominant) hand more than twice as often as his left to gesture during negative statements, McCain was 12 times as likely to do so. (McCain injured both arms, particularly his nondominant right arm, during his crash landing and captivity in the Vietnam War.) In 2004, Kerry’s ratio was about 3-to-1, but Bush broke even, using his left (nondominant) hand while making 20 positive statements and 19 negative ones.

Despite the use of right and left metaphors to describe conservative and liberal politics, the study found party affiliation had no effect on the results. The implicit association between a positive or negative statement and the selection of a hand for gesturing “is something that Democrats and Republicans appear to agree on,” according to Casasanto and his co-author at the Planck Institute, Kyle Jasmin..