Effects of cost and praise-seeking need on motive inference for those who engage in helping behaviours

This study revealed determinants that influence motive inference toward helpers who engage in lifesaving. The costly signalling theory contends that higher costs associated with helping behaviour will promote one's inference of altruistic motives toward a helper. We examined how costs affect third parties' motive inference when controlling for benefits to recipients. In addition, in terms of projection theory, we predicted that the stronger the third parties' praise-seeking need, the more likely it is they will infer self-presentational motives toward a helper. We also examined if the praise-seeking need would moderate the effect of cost on motive inference. Two vignette studies using hypothetical scenarios were conducted. In Study 1 (N = 140) and Study 2 (N = 100), the main effect of costs was found to be significant, indicating that the larger the cost, the more likely it is that a third party inferred altruistic motives toward a helper. Moreover, the main effect (but not the moderation effect) of the praise-seeking need was also significant, as predicted above. This study provides stronger support for the costly signalling theory and reveals an individual-difference factor that determines motive inference toward a helper.