UC San Diego

Information processing is required for any social thought, decision, or action. Most past and current research in social cognition focuses solely on the content of the information being conveyed. While this is clearly important, in this dissertation, I investigate how basic social responses (i.e., rapid perceptions, judgments, and actions) are impacted by the dynamics of information processing (i.e., its ease, speed, or coherence). To do this, I examine two key determinants of processing dynamics — familiarity (prior stimulus experience) and fluency (ease of stimulus processing). First, Chapter 1 provides a systematic investigation of how familiarity influences the appeal of facial blends. Even though facial blends are usually deemed more attractive than their constituent individuals, Chapter 1 demonstrates that this classic beauty-in-averageness effect reverses when the individuals are highly familiar (thus, an ugliness-in-averageness effect). Second, Chapter 2 extends the examination of familiarity to basic effects on perception, in showing that facial expressions from familiar individuals appear happier. These results also suggest that the familiarity-positivity effect functions by selectively enhancing positive stimulus features, rather than reducing negative stimulus features. Third, Chapter 3 moves towards gauging how categorization fluency (or the effort needed to determine category membership) influences the seemingly automatic discomfort people feel towards “mixed” agents (or those containing human and non-human features, like androids). Chapter 3 shows that classifying on the ambiguous human-likeness dimension makes the mixed agents (androids) more disfluent, and in turn, more disliked. Therefore, these results offer evidence that negative reactions to mixed agents are not obligatory, but instead are dependent on the surrounding judgment and context. Finally, Chapter 4 explores the link between fluency and motivation-related action. These experiments demonstrate that fluency elicits context-sensitive approach action-tendencies (i.e., RTs to initiate arm flexion), which are accompanied by physiological responses indicative of positive affect (i.e., increased smiling and reduced frowning, via facial electromyography). Taken together, the current dissertation shows that familiarity and fluency are flexibly embedded into our rapid perceptions, judgments, and actions towards social stimuli.