Does oxytocin affect mind-reading? A replication study
Introduction
In oxytocin research, one of the most referenced and well-known finding constitutes its benefits on mind-reading (Domes et al., 2007). Mind-reading, i.e., the ability to infer others’ mental states, also referred to as mentalizing or cognitive empathy, is integral for social interactions (Amodio and Frith, 2006). It is regarded as being distinct from emotional empathy, i.e., the ability to emotionally share another's affective state as both enable the understanding of others’ states via different neural networks (Dziobek et al., 2008, Shamay-Tsoory et al., 2009). In general, empathy is a broad construct, consisting of both cognitive and emotional reactions to others’ experiences (see e.g., Shamay-Tsoory, 2011).
The observation from Domes et al. (2007) that oxytocin enhances interpretation of subtle social-affective cues from the eye region, measured by the Reading the Mind in the Eyes Test (RMET), has only recently been fully replicated (Feeser et al., 2015) including both general effects and item difficulty as an additional modulator. Other oxytocin administration studies did not elicit these broad improvements on the RMET in healthy individuals (Kuypers et al., 2014, Luminet et al., 2011, Pincus et al., 2010, Riem et al., 2014, Woolley et al., 2014) and could only partially confirm increased accuracy on difficult items after oxytocin (Woolley et al., 2014). A more pronounced impact of oxytocin on difficult mental inferences might be due to the greater challenge they present to healthy participants (Feeser et al., 2015, Kuypers et al., 2014), which fits with oxytocin-induced benefits in RMET performance specifically in less socially proficient individuals (Feeser et al., 2015, Luminet et al., 2011, Riem et al., 2014) as well as clinical populations such as autism spectrum disorder (e.g., Guastella et al., 2010). Interestingly, facilitated mental state attribution after oxytocin administration for individuals scoring high on alexithymia was further moderated by the type of material, i.e., increased accuracy was driven by negative and highly intense expressions (Luminet et al., 2011). These emotion-specific effects might indicate that oxytocin influences emotional rather than cognitive processing. Likewise, in the Multifaceted Empathy Test (Dziobek et al., 2008) where stimuli include additional facial and contextual features, oxytocin enhanced the intensity of emotional reactions (emotional empathy), but not the identification of others’ mental states (cognitive empathy) (Hurlemann et al., 2010).
Taken together, these findings suggest that oxytocin effects on mind-reading depend on both baseline social-emotional abilities and properties of the environment that contribute to the interaction. As the influence of personal variability and contextual factors has been demonstrated in the domain of social cognition and other areas of oxytocin research (for a review see Bartz et al., 2011), investigating the stability and replicability of (interaction) effects remains important to evaluate its therapeutic potential.
The current study follows the randomized, double-blind, placebo-controlled, cross-over design from Domes et al. (2007) to test the impact of oxytocin on RMET performance, measured by accuracy, and potential moderation by item characteristics (difficulty, valence, intensity, sex of poser). Because previous studies vary in their choice of item categories, we aimed to thoroughly investigate in how far these different classifications yield the same result within one oxytocin administration study.
Our second aim was to determine the role of individual differences in trait empathy, assessed with two commonly used self-report inventories, the Empathy Quotient (EQ; Baron-Cohen and Wheelwright, 2004) and the Interpersonal Reactivity Index (IRI; Davis, 1983). Whereas the EQ yields an aggregated empathy score, the IRI is a multidimensional empathy questionnaire that differentiates between two subcomponents of cognitive and emotional empathy. Of these, cognitive empathy is best operationalized by the perspective-taking scale, and emotional empathy is best operationalized by the empathic concern scale. If cognitive empathy underlies mind-reading as in the RMET, improved accuracy after oxytocin administration specifically for individuals low in cognitive empathy might be expected. Alternatively, however, if oxytocin affects rather emotional than cognitive empathy (Hurlemann et al., 2010, Shamay-Tsoory, 2011), oxytocin administration should lead to facilitated performance for those low in emotional empathy.
Section snippets
Subjects
Twenty-four healthy males (Mage = 21.46 years, SD = 1.93) participated for financial compensation. All of them were students and recruited through advertisements placed across campus and in an online recruitment system (Sona System: http://radboud.sona-systems.com). The data were collected at the Donders Institute of Brain Cognition and Behavior (Nijmegen, The Netherlands) in spring 2011. Subjects were screened according to in- and exclusion criteria and received information about the study several
Results
Total RMET scores did not differ between oxytocin and placebo sessions, t(23) = .465, p = .64. Table 1 reports overall means per substance, and Table 2 reports means based on item characteristics across substances.
Discussion
In the current study, oxytocin did not influence RMET performance, neither in general nor for specific subsets of items. However, oxytocin-induced changes in mind-reading were related to emotional empathy, with greater benefits in those with lower emotional empathy. Overall, accuracy clearly differed between stimulus categories, with better recognition of easy vs. difficult items (Domes et al., 2007, Feeser et al., 2015), positive vs. negative states (Kuypers et al., 2014) and more intense vs.
Role of the funding source
Ellen de Bruijn was supported by Veni and Vidi grants from the Netherlands Organization for Scientific Research (NWO; 451-07-022 and 016-135-367).
Conflict of interest statement
None declared.
Acknowledgments
The authors thank Gregor Domes and Olivier Luminet for providing the item classifications. We are also grateful to Inti Brazil, Evelien Kostermans, and Jana Kruppa for assistance in the data collection.
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