The subjective value of a smile alters social behaviour.

Face-to-face social behaviour is difficult to explain, leading some researchers to call it the "dark matter" of psychology/neuroscience [1]. We apply an idea from neuroeconomics to this problem, suggesting that how people subjectively value facial expressions should predict usage differences during unconstrained interaction. Specifically, we ask whether the subjective value of smiles is malleable as a consequence of immediate social experience and how this relates to smiling during face-to-face interactions. We measured the value of a smile in monetary terms and found that increases in people's social neediness caused devaluation of polite smiles but no changes in how they valued genuine smiles. This result predicts that participants induced to feel high levels of social need should be less responsive to their social partners' polite smiles in a subsequent unconstrained social interaction. As expected, high social-need participants returned fewer polite smiles when interacting with a partner, leading to poor interaction outcomes. Genuine smile reciprocity remained unchanged. Findings show that social states influence real-world interactions by changing social-cue valuation, highlighting a potential mechanism for understanding the moment-to-moment control of social behaviour and how behaviour changes based on people's subjective evaluations of the social environment.

The Role of Experimenter Belief in Social Priming.

Research suggests that stimuli that prime social concepts can fundamentally alter people's behavior. However, most researchers who conduct priming studies fail to explicitly report double-blind procedures. Because experimenter expectations may influence participant behavior, we asked whether a short pre-experiment interaction between participants and experimenters would contribute to priming effects when experimenters were not blind to participant condition. An initial double-blind experiment failed to demonstrate the expected effects of a social prime on executive cognition. To determine whether double-blind procedures caused this result, we independently manipulated participants' exposure to a prime and experimenters' belief about which prime participants received. Across four experiments, we found that experimenter belief, rather than prime condition, altered participant behavior. Experimenter belief also altered participants' perceptions of their experimenter, suggesting that differences in experimenter behavior across conditions caused the effect. Findings reinforce double-blind designs as experimental best practice and suggest that people's prior beliefs have important consequences for shaping behavior with an interaction partner.