Social and Emotional Development in Pre-Adolescent Macaques Open Access

Murphy, Lauren (2015)

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Aberrant social and emotional function is a hallmark of many of neuropsychological disorders emerging during adolescence, such as depression and anxiety. To advance a mechanistic understanding of social development during this period, a primate model of adolescence is needed and will provide a vehicle for the application of novel therapies. I propose the rhesus macaque as a model due to the species social complexity and protracted childhood and adolescent period. To measure social maturation in untrained, nonverbal animals I measured behavioral changes to social and emotional stimuli using infrared eye tracking and an emotional reactivity task in three juvenile and three adult male macaques. Juveniles were tested at 18, 22, and 26 months of age, making this the first longitudinal examination of macaque adolescent social development. As measured by changes in fixation duration and frequency to the eyes and body of unknown macaques, I report normative adult patterns, as well as developmental changes, in nonhuman social and emotional processing. In adults, the eyes negative social stimuli are looked at more frequently than neutral or positive stimuli. However, this normative pattern is not seen in the late juvenile stage. At 18 months of age, macaques look longer at social stimuli generally, and usually without regard to emotion. By 22 months, this broad social attention significantly decreases within both the body and the eyes. At 26 months, fixation duration once again increases, and is now accompanied by more adult-like patterns of emotional attention. In addition to changes in fixation behavior, measures of emotional reactivity correspond with this pattern, such that 18 month olds are reactive to novel stimuli irrespective of valence, but by 22 and 26 months of age they show an adult-like pattern of increased reactivity only toward novel negative stimuli. Taken together, these data document continuing pre-pubertal changes in social and emotional attention toward an adult-like pattern in a nonhuman primate. These data lay the groundwork for future comparative studies with human subjects that may elucidate the ongoing development of social and emotional processing during the adolescent period.

Table of Contents



Subjects. 5

Research Design. 7

1. Face Processing. 7

2. Emotional Reactivity. 11

3. Statistical Analyses. 13


Eye Tracking. 15

1. Adult Scanning Patterns. 15

2. Juvenile Scanning Patterns. 16

Emotional Reactivity. 21


Adult Visual Scanning Pattern. 23

Visual Scanning Pattern During Development. 25

Emotional Reactivity During Development. 27

Future Directions. 29


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