Interference from previously learned information, known as proactive interference (PI), limits our memory retrieval abilities. Previous studies of PI resolution have focused on the role of short-term familiarity, or recency, in causing PI. In the present study, we investigated the impact of long-term stimulus familiarity on PI resolution processes. In two behavioral experiments and one event-related fMRI experiment, long-term familiarity was manipulated through the use of famous and nonfamous stimuli, and short-term familiarity was manipulated through the use of recent and nonrecent probe items in an item recognition task. The right middle frontal gyrus demonstrated greater sensitivity to famous stimuli, suggesting that long-term stimulus familiarity plays a role in influencing PI resolution processes. Further examination of the effect of long-term stimulus familiarity on PI resolution revealed a larger behavioral interference effect for famous stimuli, but only under speeded response conditions. Thus, models of memory retrieval--and of the cognitive control mechanisms that guide retrieval processes--should consider the impact of and interactions among sources of familiarity on multiple time scales.
The study of individual differences in cognitive abilities and personality traits has the potential to inform our understanding of how the processing mechanisms underlying different behaviors are organized. In the current set of studies, we applied an individual-differences approach to the study of sources of variation in individuals’ personality traits, cognitive control, and linguistic ambiguity resolution abilities. In Chapter 2, we investigated the relationship between motivational personality traits and cognitive control abilities. The results demonstrated that individual differences in the personality traits of approach and avoidance predict performance on verbal and nonverbal versions of the Stroop task. These results are suggestive of a hemisphere-specific organization of approach/avoidance personality traits and verbal/nonverbal cognitive control abilities. Furthermore, these results are consistent with previous findings of hemispheric asymmetry in terms of the distribution of dopaminergic and norephinephrine signaling pathways. In Chapter 3, we investigated the extent to which the same processing mechanisms are used to resolve lexical and syntactic conflict. In addition, we incorporated a behavioral genetics approach to investigate this commonality at the neurotransmitter level. We explored whether genetic variation in catechol-O-methyltransferase (COMT), a gene that regulates the catabolism of dopamine in prefrontal cortex, is related to individuals’ ability to resolve lexical and syntactic conflict. The results of this study demonstrated that individual differences in the ability to resolve lexical conflict are related to variation in syntactic conflict resolution abilities. This finding supports constraint satisfaction theories of language processing. We also showed that those individuals with the variant of the COMT gene resulting in less availability of dopamine at the synapse tended to have greater difficulty processing both lexical and syntactic ambiguities. These results provide novel evidence that dopamine plays a role in linguistic ambiguity resolution. In sum, the results from the current set of studies reveal how an individual-differences approach can be used to investigate several different factors involved in the contextdependent regulation of behavior. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Psychology First Advisor Sharon L. Thompson-Schill
Humans not only have impressive executive abilities, but we are also fundamentally social creatures. In the cognitive neuroscience literature, it has long been assumed that executive control mechanisms, which play a critical role in guiding goal-directed behavior, operate on consciously processed information. Although more recent evidence suggests that unconsciously processed information can also influence executive control, most of this literature has focused on visual masked priming paradigms. However, the social psychological literature has demonstrated that unconscious influences are pervasive, and social information can unintentionally influence a wide variety of behaviors, including some that are likely to require executive abilities. For example, social information can unconsciously influence attention processes, such that simply instructing participants to describe a previous situation in which they had power over someone or someone else had power over them has been shown to unconsciously influence their attentional focus abilities, a key aspect of executive control. In the current review, we consider behavioral and neural findings from a variety of paradigms, including priming of goals and social hierarchical roles, as well as interpersonal interactions, in order to highlight the pervasive nature of social influences on executive control. These findings suggest that social information can play a critical role in executive control, and that this influence often occurs in an unconscious fashion. We conclude by suggesting further avenues of research for investigation of the interplay between social factors and executive control.
