Positivity can cue familiarity.

Given that familiarity is closely associated with positivity, the authors sought evidence for the idea that positivity would increase perceived familiarity. In Experiment 1, smiling and thus positively perceived novel faces were significantly more likely to be incorrectly judged as familiar than novel faces with neutral expressions. In Experiment 2, subliminal association with positive affect (a positively valenced prime) led to false recognition of novel words as familiar. In Experiment 3, validity judgments, known to be influenced by familiarity, were more likely to occur if participants were in happy mood states than neutral mood states. Despite their different paradigms and approaches, the results of these three studies converge on the idea that, at least under certain circumstances, the experience of positivity itself can signal familiarity, perhaps because the experience of familiarity is typically positive.