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                            University of Pennsylvania
ScholarlyCommons
	Summer 8-13-2010
Looking Through the Lens of Individual Differences: Relationships Between Personality, Cognitive Control, Language Processing, and Genes
	Ranjani Prabhakaran
		Recommended Citation
	Looking Through the Lens of Individual Differences: Relationships Between Personality, Cognitive Control, Language Processing, and Genes
		Abstract
		Degree Type
		Degree Name
		Graduate Group
		First Advisor
		Keywords
		Subject Categories
Prabhakaran_Dissertation_2010_FINAL
                        
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University of Pennsylvania
ScholarlyCommons

Publicly Accessible Penn Dissertations

Summer 8-13-2010

Looking Through the Lens of Individual
Differences: Relationships Between Personality,
Cognitive Control, Language Processing, and
Genes
Ranjani Prabhakaran
University of Pennsylvania, [email protected]

Follow this and additional works at: http://repository.upenn.edu/edissertations

Part of the Biological Psychology Commons, and the Cognitive Psychology Commons

This paper is posted at ScholarlyCommons. http://repository.upenn.edu/edissertations/426
For more information, please contact [email protected]

Recommended Citation
Prabhakaran, Ranjani, "Looking Through the Lens of Individual Differences: Relationships Between Personality, Cognitive Control,
Language Processing, and Genes" (2010). Publicly Accessible Penn Dissertations. 426.
http://repository.upenn.edu/edissertations/426

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Abstract
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 context-
dependent regulation of behavior.

Degree Type
Dissertation

Degree Name
Doctor of Philosophy (PhD)

Graduate Group
Psychology

First Advisor
Sharon L. Thompson-Schill

Keywords
individual differences, cognitive control, personality, language processing, behavioral genetics, dopamine

This dissertation is available at ScholarlyCommons: http://repository.upenn.edu/edissertations/426

http://repository.upenn.edu/edissertations/426?utm_source=repository.upenn.edu%2Fedissertations%2F426&utm_medium=PDF&utm_campaign=PDFCoverPages

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A second goal of the current study was to explore the neurobiology of these language

processes. The neuroimaging and neuropsychological studies discussed above have shed

light on the neural systems underlying lexical and syntactic ambiguity resolution.

However, less is known about the neurotransmitter systems underlying these processing

mechanisms. The importance of dopamine for prefrontal cortical function and cognitive

control has been demonstrated in several studies (e.g. Braver & Barch, 2002; Cohen,

Braver, & Brown, 2002; Goldman-Rakic, 1996; Miller & Cohen, 2001). A single

nucleotide polymorphism in the gene coding for catechol-O-methyltransferase (COMT),

an enzyme involved in the catabolism of dopamine, has been linked to individual

differences in cognitive control abilities (e.g. Blasi et al., 2005; Bruder et al., 2005;

MacDonald, Carter, Flory, Ferrell, & Manuck, 2007; Mattay et al., 2003; see Goldberg &

Weinberger, 2004 for a review). The substitution of a single methionine (met) amino

acid instead of valine (val) at codon 158 leads to lower levels of COMT activity, resulting

in greater availability of dopamine at the synapse (Goldberg & Weinberger, 2004).

Individuals homozygous for the val allele tend to have lower availability of dopamine at

the synapse. These individuals also tend to demonstrate impaired performance on tasks

with cognitive control demands, such as the Wisconsin Card Sorting Task, compared to

individuals homozygous for the met allele (e.g. Blasi et al., 2005; Bruder et al., 2005;

MacDonald et al., 2007; Mattay et al., 2003, c.f. Ho, Wassink, O’Leary, Sheffield, &

Andreasen, 2005; Tsai et al., 2003). Despite the emphasis on variation in the COMT

val158met polymorphism and its relationship with individual differences in cognitive

control abilities, there have been few studies that have investigated how COMT variation

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impacts linguistic ambiguity resolution abilities. Reuter, Montag, Peters, Kocher, &

Keifer (2009) recently investigated the role of the COMT val158met polymorphism in

lexical and semantic processing. Although the authors failed to find a significant

association between genetic variation in COMT and semantic priming effects, they found

that subjects homozygous for the met allele demonstrated faster lexical decision latencies

compared to individuals carrying at least one val allele.

Based on this finding and the numerous studies implicating the COMT val158met

polymorphism in cognitive control abilities, we investigated the role of this

polymorphism in both lexical and syntactic ambiguity resolution in the current study.

Specifically, we predicted that individuals with the val/val COMT genotype would

demonstrate exaggerated conflict effects across both the lexical and syntactic ambiguity

resolution tasks compared to those individuals with the met/met COMT genotype.



Methods

Participants

Seventy-one participants (47 women, 24 men, ages 18-35) participated in this study.

Data from nine additional participants were excluded from all analyses for the following

reasons: at-chance performance on the lexical ambiguity resolution task (six subjects) and

technical difficulties with data collection in the syntactic ambiguity resolution task (three

subjects). All subjects were right-handed, native speakers of English, and were not

taking any psychoactive medications. The 71 participants comprised the following racial

and ethnic backgrounds: 56 Caucasian, 5 African American, 1 Asian, 1 Hispanic, and 8

Page 107

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