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  • Addiction, Drugs
  • Information from Lay-Language Summaries is Embargoed Until the Conclusion of the Scientific Presentation

    853—Social Cognition: Behavior and Pharmacology

    Wednesday, November 13, 2013, 1:00 pm - 5:00 pm

    853.02: The opioid system mediates perceived facial attractiveness and attention to others’ eyes

    Location: Halls B-H

    *O. CHELNOKOVA, B. LAENG, S. LEKNES;
    Dept. of Psychology, Univ. of Oslo, Oslo, Norway

    Abstract Body: Of all facial features the eyes are typically attended the most. Looking someone in the eyes is rewarding, and facial attractiveness increases activity in the brain’s reward circuits when gaze is direct as opposed to when it is averted. The human brain reward system is rich in both dopamine and opioid receptors. There is increasing evidence for opioid system involvement in reward processing.
    We assessed the role of the human opioid system in a basic social reward: looking at someone’s eyes. In this randomized double blind cross-over study, 30 males received a µ-opioid agonist (morphine 10 mg), a non-selective opioid antagonist (naltrexone 50 mg) or placebo (per-oral) on three separate days. Participants viewed photos of faces while their eye movements were recorded. Facial stimuli varied in attractiveness and included photos with both direct and averted gaze. Fixation time for selected regions of interest of female faces was analyzed in a multiple regression analysis.
    Facial attractiveness affected scan patterns so that less time was spent looking at the eyes and more at the nose-mouth region of the least attractive females. We also observed a linear effect of the opioid drug manipulation on looking time for the eye region, such that morphine increased and naltrexone decreased the time spent fixating on the eyes of females.
    Overall, our results illustrate the rewarding nature of looking at eyes, and demonstrate the role of opioids in mediating attention to this socially significant facial region.

    Lay Language Summary: Our research is the first to demonstrate that the brain’s endorphin system helps determine how attractive we find other people. Moreover, activating the endorphin system increased the amount of time spent looking people in the eyes. Blocking this system had the opposite effect.
    The human brain finds reward in looking at beautiful faces, and of all facial features the eyes are typically attended to the most. They provide the most socially relevant information about others' emotional state and intentions. Looking someone in the eyes is rewarding, and activity in the brain’s reward circuits also increases when looking at attractive faces gazing in our direction. The human reward system is rich in opioid (endorphin) receptors, and there is increasing evidence for endorphin system involvement in processing rewards of various types.
    We assessed the role of the human opioid system in a basic social reward: looking at someone’s eyes. In our study, 30 healthy males had their endorphin system stimulated with an endorphin agonist (morphine), deactivated with an antagonist (naltrexone) or left unaltered with placebo on three separate days. They were asked to rate attractiveness of faces while their eye movements were recorded. We hypothesized that morphine would increase attractiveness ratings, as well as the time spent looking at the eyes of the faces, while the opposite results would be observed with the endorphin antagonist.
    Overall, faces were rated as more attractive after morphine treatment, compared to the naltrexone condition. Interestingly, this effect was most pronounced for the most attractive faces of the opposite sex. We also confirmed our predictions by observing that morphine increased and naltrexone decreased the time spent looking at the eyes of the faces.
    Preference for beautiful members of our own species can be seen as an evolutionary tool to promote survival and procreation, since attraction towards others is a main component of pair-bonding and attachment. Here, we provide the first causal evidence that the endorphin system mediates face attractiveness perception in humans. The current study offers important insight about the mechanisms of the brain systems that mediate human attention and gaze to the eyes of others. Overall, our findings show that studying the brain endorphin system is an important part of the quest to solve the mysteries of human attachment.