Methods
Participants. The younger and older participants recruited for
Study 1 also took part in Study 2.
Stimuli and procedure. We created face pairs with the stimuli
from Study 1. Three face pairs were created for each of the
individuals displaying the expressions. Within each face pair, both
images were of the same identity but displayed different expressions.
In one pair, a nonenjoyment smile was coupled with an
enjoyment smile. In the other two face pairs, the images of neutral
expressions were paired with either enjoyment smiles or nonenjoyment
smiles, respectively.
Thirty-nine face pairs (13 in each condition) were randomly
presented to participants. Each pair of faces was presented side by
side on a computer screen, and location (i.e., left or right) of the
expressions was counterbalanced. Participants were told that in
each trial they would see two photographs of the same person on
the screen but that the photographs had been taken at different
times (e.g., the one on the left was taken on Monday at 10 a.m.,
and the one on the right was taken on Tuesday at 10 a.m.).
Participants were instructed to indicate, with a keypress, which
time they would rather ask that person for a favor. Participants
received four practice trials.