Reward Dependence: Personality and Neurological Correlates of Social Behavior Open Access

Abstract

Abstract
Reward Dependence: Personality and Neurological Correlates of Social Behavior

The neural mechanisms of cooperative behavior have been studied from many angles.
This study aimed to correlate personality measures with behavior, brain function, and brain
structure during a simulation of genuine social interaction to increase our understanding of the
mechanisms and individual variation of prosocial behavior. 185 individuals between the ages of
18 and 22 (mean=20.2) were scanned using fMRI while playing an economic decision making
game with perceived human partners. Personality data were collected after the scan using the
Temperament and Character Inventory. Behavioral results showed sexually dimorphic effects of
personality on behavior in social economic decision making game. Using fMRI, both reward
dependence and cooperativeness were shown to be correlated with amygdala activation in
response to unreciprocated cooperation in females, while activation in the medial prefrontal
cortex after a negative outcome was correlated with cooperativeness in males. Grey matter
volume was correlated with cooperativeness in the dlPFC and right amygdala in males.
Cooperativeness was also correlated with grey matter volume in the left insula extending into
opercular cortex, in both males and females. Reward dependence was correlated with grey
matter volume in the right amygdala in females. These results implicate the amygdala as a
structure not only responsible for the affective response to negative social behavior, but also
for increasing the saliency of negative social interactions, resulting in prosocial behavior to
avoid negative situations. In addition, areas implicated in theory of mind and empathy, such as
the mPFC and insula, were correlated with cooperativeness, but not reward dependence in
males, showing differing neural mechanisms between the similar measurements. Finally, the
lack of overlap in many of the conditions between males and females demonstrate sexual
dimorphism in the neural mechanisms of cooperative behavior and possible different
evolutionary constraints at work in males and females.

Table of Contents

Table of Contents

I. Introduction........................................................................................................................1
a. Evolutionary origins of cooperative behavior...........................................................................1
b. Quantifying cooperative behavior..........................................................................................4
c. Figure 1.............................................................................................................................5
d. Quantifying personality traits................................................................................................6
e. Neuroimaging ....................................................................................................................7
f. Previous research................................................................................................................9
g. Aims and hypotheses..........................................................................................................9
II. Methods..........................................................................................................................12
a. Subjects...........................................................................................................................12
b. Behavioral procedure.........................................................................................................12
c. Task procedure ................................................................................................................13
d. Personality data procedure ................................................................................................14
e. Behavioral analysis...........................................................................................................14
f. Figure 2...........................................................................................................................14
g. MRI image acquisition.......................................................................................................15
h. fMRI image analysis..........................................................................................................15
i. Structural data analysis .....................................................................................................15
III. Results..........................................................................................................................17
a. Personality results............................................................................................................17
b. Figure 3..........................................................................................................................17
c. Emotional results.............................................................................................................18
d. Behavioral results............................................................................................................18
e. Figure 4..........................................................................................................................18
f. Figure 5...........................................................................................................................19
g. Functional results.............................................................................................................20
h. Figure 6..........................................................................................................................20
i. Structural results...............................................................................................................21
j. Figure 7...........................................................................................................................21
k. Figure 8..........................................................................................................................22
l. Figure 9...........................................................................................................................23
m. Figure 10........................................................................................................................23
IV. Discussion......................................................................................................................24
a. Personality.......................................................................................................................24
b. Emotional........................................................................................................................25
c. Behavioral.......................................................................................................................25
d. Functional.......................................................................................................................26
e. Structural........................................................................................................................27
V. Tables.............................................................................................................................32
a. Table 1............................................................................................................................32
b. Table 2............................................................................................................................32
IV. References.....................................................................................................................34

About this Honors Thesis

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School	Emory College
Department	Anthropology
Degree	BS
Submission	Honors Thesis
Language	English
Research Field	Psychology, Psychobiology Biology, Neuroscience Anthropology, Physical
Keyword	Voxel-based morphometry TCI functional MRI amygdala
Committee Chair / Thesis Advisor	Rilling, James K, Emory University
Committee Members	Marsteller, Pat, Emory University Stout, Dietrich, Emory University

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