In a placebo-controlled double-blind between-subject design experiment, investigators plan to investigate whether oral (lingual spray) oxytocin influences human top-down attention via the oxytocin receptor and whether its effects are dose- and task-dependent. Subjects complete questionnaires in Chinese versions before treatment administration, including Behavioral Activation System scale, Behavioral Inhibition System scale,Trait Anxiety Inventory, State Anxiety Inventory, Liebowitz Social Anxiety Scale, Beck Depression Inventory, Autism Spectrum Quotient. Then the first blood (6ml via indwelling medial cubital vein catheter) and saliva (1-2 ml, passive drool) samples are collected, followed by the first self-administered medication (three sublingual and three supragingival administrations, alternating separated by 30 seconds). After a 15-minute interval, the second medication is administered, with a second blood sample collected immediately afterwards. Subjects then remain in the lab for 30 minutes (mobile phone use and conversation with experimenters are prohibited during this period). Behavioral experiment (antisaccade) commences after the third blood collection. During these phases, subjects' latency of correct trials, error rate and pupil size in response to stimuli will be measured using eye tracking equipment. Immediately after completion of the paradigm subjects will complete the state anxiety questionnaire again to assess treatment/paradigm effects on anxiety.

A Mixed linear model, followed by appropriate post-hoc analyses will be used on eye-tracking and other data to assess treatment effects. Correlation analysis will be used to assess associations between latency of correct trials in prosaccade and error rate in antisaccade in the different groups. Investigators make the following hypotheses according to our previous studies: first, oral oxytocin treatment will dose-dependently decrease top-down attention to social but also non-social stimuli; secondly, oxytocin concentrations will be dependent on the dose of oral administration and will not be influenced by oral administration of the oxytocin receptor antagonist (atosiban) administration; thirdly, atosiban is anticipated to have the opposite effect of oral oxytocin and may not interfere with top-down attention; fourthly, oxytocin treatment will increase pupil diameter while viewing social stimuli; fifthly, there will be treatment- dependent effects on post-task state anxiety scores; lastly, antisaccade performance in each group might be influenced by subjects' scores on autistic traits.