Abstract: The inhibition of return (IOR) promotes the exploration of new and previous unattended objects in the scene during visual search or foraging by preventing attention from returning to already-attended objects. Many lines of evidence have shown that the different kinds of emotions have significant influence on the magnitude of inhibition of return (IOR) in the cue-response paradigm. Human faces, as the social and biological stimulus, play an important role in our social life, and face-gender information is also important in our social activity, especially during face-to-face communications. However, it still remains largely unknown how the face-gender information affects IOR and what the difference is between sexes in IOR effects. Using the cue-target paradigm as used in other studies, in the present study we explored the sex difference in IOR effect in the face-gender discrimination task. During the cue period, a green colored box (cue) was first shown on either the right or left side of a monitor screen with equal probability for 200 ms, which was followed by a central cue. Then, the target face (either a male or a female face with neutral emotion, randomly arranged) was then appeared on the valid position (the same position the cue had been) or invalid position (the position in the other side of the cue) with equal probability after the offset of central cue. Subjects were asked to discriminate the gender of the target face by pressing a button out of two as accurately and quickly as possible. We collected behavioral data from each subject, including correct rate and reaction time. Forty-six college participants including 22 males and 24 females were recruited in the present study. Our data showed that the reaction time to face-gender in valid-cued locations was significantly longer than that in invalid-cued locations, which indicates that there exists IOR in the face-gender discrimination task. Furthermore, the male subjects did not show any difference in the magnitude of IOR between male and female faces, which indicates that face-gender has no effect on IOR effects in the face-gender discrimination task. However, the average magnitude of IOR for male faces in female participants in their follicular phase was smaller than those participants in their luteal phase, which suggests that the magnitude of IOR is related to the interaction of face-gender and the menstrual period of the female subjects. Our data show that IOR in the face-gender discrimination task does not show any sex difference. We therefore provide evidence for the ‘blind’ mechanism of IOR in the present study. However, the difference in magnitude of IOR between different menstrual periods of female subjects suggests that the effect of face-gender on IOR relies on the participants' sensitivity to gender and sex information.

Key words: inhibition of return (IOR), face-gender, sex difference