Unchanged food approach-avoidance behaviour of healthy men after oxytocin administration

The oxytocinergic system has been assumed to contribute to food intake, possibly via interactions with dopamine. However, so far, it is unknown whether oxytocin influences the underlying motivational behaviour towards food. In the present study, we used a food-based approach-avoidance task (AAT) in a randomised, placebo-controlled, double-blind, cross-over design to compare intranasal oxytocin with a placebo. In the AAT, participants pushed or pulled a joystick when images of foods with a high or low craving rating were presented, where differences in response times typically reflect approach and avoidance motivational biases towards positively and negatively valence stimuli, respectively. Thirty-three healthy male participants (age = 25.12 ± 3.51 years; body mass index = 24.25 ± 2.48 kg/m² ) completed the two-session study, one with placebo and the other with oxytocin. We used mixed-effects models to investigate effects of treatment (oxytocin, placebo), response type (approach, avoid) and stimulus (high, low craving). The results showed that both approach and avoid responses tended to be faster for foods higher in craving compared to foods lower in craving. Most importantly, we did not observe any significant effects of oxytocin compared to placebo in motivational behaviour towards food. Our study demonstrates a general response bias towards foods with different craving values, which could have implications for future studies investigating food-related behaviour. We discuss possible explanations for the null effects of oxytocin and suggest further investigation of the relationship between oxytocin, dopamine and food-reward processing.

The influence of gaze direction on food preferences

In our information-rich environment, the gaze direction of another indicates their current focus of attention. Following the gaze of another, results in gaze-evoked shifts in joint attention, a phenomenon critical for the functioning of social cognition. Previous research in joint attention has shown that objects that are attended by another are more liked than ignored objects. Here, we investigated this effect of gaze-cueing on participants' preferences for unknown food items. Participants provided their willingness to pay (WTP), taste and health preferences for food items before and after a standard gaze-cueing paradigm. We observed a significant effect of gaze-cueing on participants' WTP bids. Specifically, participants were willing to pay more money for the food items that were looked at by another person. In contrast, there was a decrease in preference for the food items that were ignored by another person. Interestingly, this increase in WTP occurred without participants' awareness of the contingency between the cue and target. These results highlight the influence of social information on human choice behavior and lay the foundation for experiments in neuromarketing and consumer decision making.

Access to awareness of direct gaze is related to autistic traits

BACKGROUND

The atypical processing of eye contact is a characteristic hallmark of autism spectrum disorder (ASD). The severity of these symptoms, however, is thought to lie on a continuum that extends into the typical population. While behavioural evidence shows that differences in social cognitive tasks in typically developed (TD) adults are related to the levels of autistic-like traits, it remains unknown whether such a relation exists for the sensitivity to direct gaze.

METHODS

In two experiments, we measured reaction times to detect the faces with direct and averted gaze, suppressed from awareness, i.e. the access to awareness. In experiment 1, we tested N = 19 clinically diagnosed adults with ASD and N = 22 TD matched controls, while in experiment 2, we tested an independent sample of N = 20 TD adults.

RESULTS

In line with the literature, experiment 1 showed preferential processing of direct gaze in the TD group but not in the ASD group. Importantly, we found a linear relationship in both experiments between the levels of autistic traits within the groups of TD participants and their sensitivity to direct gaze: with increasing autistic characteristics, there was a decrease in sensitivity to direct gaze.

CONCLUSION

These results provide the first evidence that differences in gaze processing and the sensitivity to direct gaze are already present in individuals with subclinical levels of autistic traits. Furthermore, they lend support to the continuum view of the disorder and could potentially help in an earlier diagnosis of individuals at high risk for autism.

Making eye contact without awareness

Direct gaze is a potent non-verbal signal that establishes a communicative connection between two individuals, setting the course for further interactions. Although consciously perceived faces with direct gaze have been shown to capture attention, it is unknown whether an attentional preference for these socially meaningful stimuli exists even in the absence of awareness. In two experiments, we recorded participants' eye movements while they were exposed to faces with direct and averted gaze rendered invisible by interocular suppression. Participants' inability to correctly guess the occurrence of the faces in a manual forced-choice task demonstrated complete unawareness of the faces. However, eye movements were preferentially directed towards faces with direct compared to averted gaze, indicating a specific sensitivity to others' gaze directions even without awareness. This oculomotor preference suggests that a rapid and automatic establishment of mutual eye contact constitutes a biological advantage, which could be mediated by fast subcortical pathways in the human brain.