Across four experiments, perceptions of social worth mediated
the effects of beneficiaries’ gratitude expressions on helpers’
prosocial behavior. The experiments showed these effects for
prosocial behavior directed toward the same beneficiary (Experiments
1 and 4), a different beneficiary (Experiment 2), and a
university (Experiment 3). In addition, gratitude expressions increased
both the initiation and maintenance of prosocial behavior,
motivating participants to provide help a second time when asked
(Experiments 1 and 2) and to persist longer in their current helping
activities without being asked (Experiments 3 and 4). These convergent
effects on objective prosocial behaviors are important,
given that the majority of gratitude research has focused on psychological
effects, leading psychologists to call for more research
on its behavioral effects (Tsang, 2006). The present research
answers these calls by demonstrating the causal impact of gratitude
on helpers’ concrete, observable prosocial behaviors. The consistently
strong effects of relatively small gratitude manipulations are
noteworthy (Prentice & Miller, 1992). In our first two experiments,
a mere expression of thanks more than doubled the likelihood that
helpers would provide assistance again (from 25% to 55% and
from 32% to 66%). In our third experiment, gratitude produced
more than 50% increases in the number of calls that the average
fundraiser made in a single week. In our fourth experiment, a
single gratitude expression yielded an increase of 15% in the
average amount of time spent helping.