The Sex-dependent Effect Of Intranasal Oxytocin On The Perception Of Eye Gaze Direction

Changes in human faces can convey a variety of social information,the most important of which are facial expressions and eye gaze information.Though facial expressions deliver numerous social communication information,eye gaze is the key to understanding others'mental intentions.The judgement of gaze direction is crucially involved in the social communication.It is the basis of the joint attention,and a foundation of human social cognition and language development.Over the last decades,researches have found that a nine-amino acid,named oxytocin?OXT?,can adjust gaze to others'eye region to affect emotion recognition.However,there is few studies about whether OXT have a direct influence on the perception of ambiguous eye gaze direction.In addition,recent studies have found that there is a sex-dependent OXT difference on the social recognition.Then,if OXT affects the perception of eye gaze direction,whether this effect can be regulated by the participants'gender?So far,it is no answer to this question.And the discussion of this issue is of great significance for the application of OXT to improve the social cognitive function of special individuals such as autism,anxiety and depression.Therefore,the current study attempted to use two behavioral experiments to investigate how oxytocin affects the judgement of ambiguous eye gaze direction,and whether this effect of OXT can be modulated by participants'gender and facial expressions.The two tasks are the cone of direct gaze task and the same-different task about the facial identity,respectively.Using the cone of direct gaze task with eleven gaze angles and three facial expressions?anger,fear,neutral?in experiment 1,participants were asked to judge the gaze direction of direct,left,or right.A logistic function in Matlab was calculated the cone of direct gaze?CoDG?under each condition for each subject,a wider CoDG means that people tended to judge one face was looking towards them.Results showed that participants'gender moderated the effect of OXT on the perception of gaze direction.In particular,oxytocin increased the CoDG in women,whereas it decreased the CoDG in men.The CoDG for men was marginally wider than that for women in the placebo?PLA?condition,however there was no difference for men and women in the OXT condition.In experiment 2,we used the two boundary gaze angles?0°,4°?for the CoDG and the same facial expressions?anger,fear,neutral?in the experiment 1 with six different virtual models?3 female,3 male?.Participants were asked to complete a same-different facial identity task,that was to judge whether the two facial identities was same or not.According to the different gaze directions about the two facial identities,the two conditions were:gaze congruent direction and gaze incongruent direction.The aim of this experiment was toexplore whether OXT have an effect on the perception of ambiguous eye gaze direction and this effect would be modulated by participants'gender and facial expressions.The key logic of this experiment was that if the drug,participants'gender and facial expressions influenced the perception of ambiguous eye gaze direction,then,1)if this effect was to make the perception of the boundary gaze angles tended to the direct gaze,the difference of gaze congruent/incongruent directions on the“yes”response in the facial identity congruent condition would be reduced;2)if this effect was to make the perception of the boundary gaze angles tended to the averted gaze,the difference of gaze congruent/incongruent directions on the“yes”response in the facial identity congruent condition would be enhanced.Results showed that 1)For accuracy,facial expressions affected the D_ACC(D_ACC=ACC _incongruence-ACC _congruence)on the“yes”response,the D_ACCCC of fear and anger was smaller than neutral.The effect of facial expressions on the gaze direction was moderated by drug.Specifically,anger had a higher accuracy in the gaze congruent direction than the gaze incongruent direction under the OXT condition,whereas there was no difference between the gaze congruent and incongruent directions for angry face in the PLA condition.On the contrary,there was a opposite pattern for the fearful expression.In the PLA condition,fear had a higher accuracy in the gaze congruent direction than the gaze incongruent direction.However,the difference between the gaze congruent direction and the gaze incongruent direction was disappeared.And there was no influence about participants'gender.2)For RTs,we found the effect of facial expressions on the D_RT(D_RT=RT _{incongruence-}RT _congruence)on the“yes”response,the D_RTT of fear and anger was smaller than neutral.Importantly,there was a significant interaction among drug,participants'gender and gaze direction congruence.Males had a great different response between the gaze congruent and incongruent direction in the PLA condition,while it disappeared in the OXT condition.Contrary to male subjects,the response for female in the gaze congruent condition was faster than the gaze incongruent condition both in the PLA and OXT conditions.Based on the two experiments in this study,we got the following conclusions:?1?Participants'gender moderated the effect of Oxytocin?OXT?on the perception of eye gaze direction.?2?There was a opposite pattern for male and female participants after the intranasal OXT.In the cone of direct gaze task,OXT significantly increased the CoDG for female participants,while it decreased the CoDG for male participants.In the same-different facial identity task,after the intranasal OXT,the difference between the gaze the gaze congruent and incongruent direction for male participants was abolished,whereas there was still a significant difference between the gaze the gaze congruent and incongruent direction for female participants.?3?The effect of OXT on the perception of eye gaze direction was affected by facial expressions only in the same-different facial identity task on accuracy.