Spencer Waters, Brigham Young University
Social condition may predict alcohol consumption in both humans and rhesus macaques (Macaca mulatta). A recent (unpublished) study in our lab showed that rhesus macaques who are living in social groups drink significantly less alcohol when compared to subjects drinking alone; furthermore, social setting modulated biological and social risk factors associated with increased alcohol consumption (i.e. serotonin transporter genotype, rearing, etc.). This project aims to further investigate the role of peer influence within rhesus macaque social groups on individual rates of alcohol consumption. Specifically, this project proposes that the quantity of alcohol consumed by an individual rhesus macaque may be influenced by the amount of alcohol consumed by their peers. Data were collected from 109 socially-housed adult rhesus macaques (37 males, 72 females) over 7 years. An aspartame-sweetened 8.4% alcohol-water solution and its sans-alcohol vehicle were available for subjects to consume for 1 hour a day over 5-7 weeks. The serotonin transporter genotype (LL and LS) for each monkey was determined using polymerase chain reaction followed by gel electrophoresis. Within-rearing group z-scores were calculated for each peer-reared and then each mother-reared monkey, thus giving a standardized measure of whether individuals were below or above their rearing group mean. The relationship between an individual monkey’s alcohol consumption z-score and peer influence was the chief interest of to this study. Peer influence according to rearing was measured by calculating the percentage of social-mates who were peer-reared (typically known to consume more alcohol) within each social cohort. Analyses were performed to assess deviation from the overall rearing group mean alcohol intake as stratified by the percentage of peer-reared subjects within each social cohort. A similar set of analyses were also performed using within-serotonin-transporter-genotype (i.e. LL or LS) group z-scores and the percentage of LS-genotype (typically shown to consume more alcohol) social mates to assess the relationship between individual alcohol intake and peer influence according to genotype. Simple linear regressions were performed using the alcohol consumption z-scores and social-mate percentages. No significant relationship was found between the percentage of LS monkeys and alcohol consumption z-scores. There was, however, a significant relationship (p = 0.003, r = 0.477) between the percentage of peer-reared social-mates and the alcohol consumption z-scores. In other words, as the percentage of peer-reared social-mates increased, so too did the relative consumption of alcohol comparative to the average of other socially-caged monkeys.