Person:

Powell, Lindsey

This dissertation engages in two major hypotheses regarding infants' naïve theory of social relationships. First, it proposes that infants may apply a domain-specific understanding to represent and reason about social groups defined by affiliation amongst their members. Second, it argues that infants may have an understanding of the causal role that behavioral conformity plays in promoting affiliation, and that this understanding may help to determine how infants reason about the coalitional social groups referred to in the first hypothesis. Experiments across three chapters address different aspects of these hypotheses. The experiments in Chapter 2 ask whether infants selectively use coalitional groups to make certain sorts of behavioral inferences, in contrast to the inferences they draw regarding other animate and inanimate categories. The experiments in Chapter 3 investigate the role of similarity of appearance in infants' representations of coalitional groups. Finally, the experiments in Chapter 4 look at how infants evaluate behavioral conformity and what they think it indicates about the attitudes of conformers and their targets. Chapter 5 synthesizes this work and discusses how it might apply to the study of imitation in both developmental and comparative fields.

Although humans generally experience a coherent sense of selfhood, we can, nevertheless, articulate different aspects of self. Recent research has demonstrated that one such aspect of self—conceptual knowledge of one's own personality traits—is subserved by ventromedial prefrontal cortex (vMPFC). Here, we examined whether an alternative aspect of “self”—being an agent who acts to achieve one's own goals—relies on cognitive processes that overlap with or diverge from conceptual operationalizations of selfhood. While undergoing fMRI, participants completed tasks of both conceptual self-reference, in which they judged their own or another person's personality traits, and agentic self-reference, in which they freely chose an object or watched passively as one was chosen. The agentic task failed to modulate vMPFC, despite producing the same memory enhancement frequently observed during conceptual self-referential processing (the “self-reference” effect). Instead, agentic self-reference was associated with activation of the intraparietal sulcus (IPS), a region previously implicated in planning and executing actions. Experiment 2 further demonstrated that IPS activity correlated with later memory performance for the agentic, but not conceptual, task. These results support views of the “self” as a collection of distinct mental operations distributed throughout the brain, rather than a unitary cognitive system.