Abstract: Prior research has shown that the time interaction partners take to make decisions can shape interpersonal perceptions and influence cooperative behavior in social dilemmas. Yet, it remains uncertain whether faster or slower decisions are more likely to foster positive impressions and promote cooperation. This study examined how decision time, as a single cue provided by interaction partners, influenced cooperative behavior in social dilemmas while controlling for other interpersonal cues. From the perspective of interpersonal perception, this study aimed to clarify the effect of decision time on cooperation and to uncover the psychological mechanisms and boundary conditions underlying this effect, thereby offering a more nuanced understanding of this important social cue.
This study employed a public goods game paradigm to measure cooperative behavior and included one pilot experiment and five formal experiments. The pilot experiment was conducted to determine appropriate time thresholds for fast and slow decision-making. Experiment 1 manipulated the decision time of an interaction partner by combining direct perception with an indirect cue, in order to assess its impact on perceived sincerity. Experiment 2a manipulated decision time in the same way to examine whether it influenced cooperative behavior through the mediating roles of perceived sincerity and cooperation expectations. Experiments 2b and 2c used either direct perception or an indirect cue alone, respectively, to examine the robustness of the findings from Experiment 2a under weaker manipulation conditions and to rule out perceived competence as an alternative explanation. Experiment 3 investigated whether and how individuals' social value orientation moderated the effect of decision time on perceived sincerity, cooperation expectations, and cooperative behavior.
The main results can be summarized as follows: (1) Individuals perceived partners who made fast decisions as more sincere than those who made slow decisions. (2) Fast decision-making promoted cooperative behavior through enhanced perceived sincerity, as well as through the chain-mediating effects of perceived sincerity and cooperation expectations. (3) The influence of decision time on cooperative behavior was moderated by social value orientation. Pro-social individuals perceived fast-deciding partners as more sincere than slow-deciding ones, which led to higher cooperation expectations and thus more cooperative behavior. In contrast, decision time did not affect pro-self individuals' perceptions of their partners' sincerity, and therefore did not influence their cooperative behavior.
These findings not only demonstrate the independent social-signaling value of partner decision time, but also reveal its dual-pathway mechanism and boundary conditions in shaping cooperative behavior in social dilemmas. The results provide new evidence that helps resolve theoretical debates concerning the interpersonal effects of decision time, and offer practical implications for optimizing cooperative strategies in real-world social dilemmas by highlighting the role of faster responses in conveying sincerity.

Key words: social dilemmas, decision time, perceived sincerity, cooperative expectations, cooperative behavior