In a double-blind, between-subject, placebo controlled design, investigators plan to investigate the effect of oxytocin treatment on the tolerance of infidelity. Male and female subjects would firstly see a neutral face of the opposite sex presented with a sentence descried their fidelity or infidelity behavior (sexual or emotional) in a relationship. Next the participant will rate the attractiveness, likability and trustworthiness of each individual, and whether they would like to have a short/long relationship with him/her. After that there will be some implicit attitude tasks to test their implicit attitude towards potential partners exhibiting previous fidelity or and infidelity.