Social hierarchies exist throughout the animal kingdom, including among humans. Our daily interactions inevitably reflect social dominance relationships between individuals. How do we mentally represent such concepts? Studies show that social dominance is represented as vertical space (i.e. high = dominant) by adults and preschool children, suggesting a space-dominance representational link in social cognition. However, little is known about its early development. Here, we present experimental evidence that 12- to 16-month-old infants expect agents presented in a higher spatial position to be more socially dominant than agents in a lower spatial position. After infants repeatedly watched the higher and lower agents being presented simultaneously, they looked longer at the screen when the lower agent subsequently outcompeted the higher agent in securing a reward object, suggesting that this outcome violated their higher-is-dominant expectation. We first manipulated agents' positions by presenting them on a podium (experiment 1). Then we presented the agents on a double-decker stand to make their spatial positions directly above or below each other (experiment 2), and we replicated the results (experiment 3). This research demonstrates that infants expect spatially higher-positioned agents to be socially dominant, suggesting deep roots of the space-dominance link in ontogeny.

Heightened experience of disgust is a feature of obsessive-compulsive disorder (OCD), particularly contamination-related OCD (C-OCD). Previous studies of the rubber hand illusion (RHI) reported that the sense of body ownership is related to the interaction between vision, touch, and proprioception. One recent study demonstrated a link between the RHI and disgust, suggesting that there is an interaction between these three perceptual modalities and disgust (Jalal et al., PLOS ONE 10:e0139159, 2015). However, there have been no direct replications of this initial study. We therefore performed a direct replication of Jalal et al.’s (PLOS ONE 10:e0139159, 2015) study. We examined 133 participants (based on a power analysis) to determine whether placing contamination-related stimuli on a rubber hand causes OCD-like disgust among healthy participants experiencing the RHI. That is, we tested whether Japanese participants experience more intense disgust when the rubber hand and the participant’s hidden hand are stroked synchronously than when stroked asynchronously, in order to replicate and examine the cross-cultural validity of this effect. The main finding of the original study by Jalal and colleagues was successfully replicated in a large sample. Some inconsistencies in one of the control procedures exploring coldness sensations during the RHI were found, which could possibly be due to cross-cultural differences or the improved statistical power of the present study. Based on the present replication study, we conclude that an intervention using the RHI as proposed by Jalal et al. (PLOS ONE 10:e0139159, 2015) might potentially be useful for the treatment of OCD following replications in clinical OCD populations.Preregistration details: This study was preregistered with Cognitive Research: Principles and Implications. The Authors’ protocol received in-principle acceptance on 31 March 2017. The preregistered protocol is available here: 10.6084/m9.figshare.6217295.

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