Oxytocin enhances pupil dilation and sensitivity to ‘hidden’ emotional expressions

Department of Psychology, University of Oslo, Postboks 1094, Blindern 0317, Oslo, Norway. .
Social Cognitive and Affective Neuroscience (Impact Factor: 7.37). 05/2012; 8(7). DOI: 10.1093/scan/nss062
Source: PubMed


Sensing others' emotions through subtle facial expressions is a highly important social skill. We investigated the effects of intranasal oxytocin treatment on the evaluation of explicit and 'hidden' emotional expressions and related the results to individual differences in sensitivity to others' subtle expressions of anger and happiness. Forty healthy volunteers participated in this double-blind, placebo-controlled crossover study, which shows that a single dose of intranasal oxytocin (40 IU) enhanced or 'sharpened' evaluative processing of others' positive and negative facial expression for both explicit and hidden emotional information. Our results point to mechanisms that could underpin oxytocin's prosocial effects in humans. Importantly, individual differences in baseline emotional sensitivity predicted oxytocin's effects on the ability to sense differences between faces with hidden emotional information. Participants with low emotional sensitivity showed greater oxytocin-induced improvement. These participants also showed larger task-related pupil dilation, suggesting that they also allocated the most attentional resources to the task. Overall, oxytocin treatment enhanced stimulus-induced pupil dilation, consistent with oxytocin enhancement of attention towards socially relevant stimuli. Since pupil dilation can be associated with increased attractiveness and approach behaviour, this effect could also represent a mechanism by which oxytocin increases human affiliation.

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Available from: Siri Leknes, Dec 13, 2013
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    • "In a study using emotional hybrid faces, Laeng et al. (2010) found that observers could not identify above chance the emotional content of such stimuli, judging them all as neutral, although the emotional expressions (happy, angry, sad or afraid) was present within the range of the lower spatial frequencies (1–6 cpi). Despite being hidden from awareness, the hidden emotional content of stimuli did stimulate the " emotional brain " , influencing the participants' friendliness evaluations: hybrid happy faces were judged as more friendly and hybrid angry faces as less friendly than neutral fac Q5 es (Laeng et al., 2010, 2013a,b; Leknes et al., 2013). This pattern of results suggests that low spatial frequencies can feed a core emotional processing of social stimuli. "
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    ABSTRACT: The valence hypothesis and the right hemisphere hypothesis in emotion processing have been alternatively supported. To better disentangle the two accounts, we carried out two studies, presenting healthy participants and an anterior callosotomized patient with ‘hybrid faces’, stimuli created by superimposing the low spatial frequencies of an emotional face to the high spatial frequencies of the same face in a neutral expression. In both studies we asked participants to judge the friendliness level of stimuli, which is an indirect measure of the processing of emotional information, despite this remaining “invisible”. In Experiment 1 we presented hybrid faces in a divided visual field paradigm using different tachistoscopic presentation times; in Experiment 2 we presented hybrid chimeric faces in canonical view and upside-down. In Experiments 3 and 4 we tested a callosotomized patient, with spared splenium, in similar paradigms as those used in Experiments 1 and 2. Results from Experiments 1 and 3 were consistent with the valence hypothesis, whereas results of Experiments 2 and 4 were consistent with the right hemisphere hypothesis. This study confirms that the low spatial frequencies of emotional faces influence the social judgments of observers, even when seen for 28 ms (Experiment 1), possibly by means of configural analysis (Experiment 2). The possible roles of the cortical and subcortical emotional routes in these tasks are discussed in the light of the results obtained in the callosotomized patient. We propose that the right hemisphere and the valence accounts are not mutually exclusive, at least in the case of subliminal emotion processing.
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    • "Given the relationship between empathy and mentalizing as well as the personal variability in OXT-induced effects, the present study aimed at investigating whether the effect of OXT depends on individual empathy scores of the participants. Previous studies have demonstrated the effect of OXT in particular for participants with low socioemotional skills (Bartz et al., 2010; Luminet et al., 2011; Quirin et al., 2011; Leknes et al., 2013). OXT has consistently been shown to enhance early allocation of selective attention toward socially relevant stimuli (Schulze et al., 2011; Domes et al., 2013). "
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    • "In this regard there is evidence showing that the administration of OT to individuals with high emotional sensitivity afforded little or no improvement in detecting subtle social cues (Leknes et al. 2013). Thus, our finding provides further support for the view suggesting that the effect of OT on sociocognitive abilities is not uniform and is susceptible to changes in context, whether it is the environment or the persons with whom we interact (Bartz et al. 2011). "
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