Predictive Tracking of Social and Non-Social Stimuli

Background and Aims: Recent research from our lab shows that infants predictive tracking of a briefly occluded moving object is sensitive to the manner by which it disappears and reappears. Five, 7-, and9-month-old infants were shown a rolling ball that briefly disappeared via kinetic occlusion or implosion (rapidly shrinking to nothing).Predictive tracking increased with age, and infants were more likely to anticipate the reappearance of the ball following occlusion than implosion. In a related series of experiments, 5- , 7-, and 9-month-oldinfants were more likely to detect a feature change of a social object than of a non-social object. If predictive tracking depends on the representation of an object, then we would expect infants to show an advantage for predictively tracking social vs. non-social objects. The purpose of the current experiment was to test this prediction by measuring predictive tracking of a briefly occluded social stimulus vs. briefly occluded non-social stimulus.Methods: A total of 10 5-month-old and 10 7-month-old infants were tested. Two different stimuli were used: (1) a multicolored ball, and (2) an animated cartoon-like figure of a woman. Both stimuli moved from left-to-right across the screen, and then reversed direction and returned to their starting location. An occluding screen was located in the middle of the objects’ paths. The objects disappeared behind the occlude via kinetic occlusion or via implosion (and reappeared via occlusion or explosion). Trials were blocked by stimulus type (social or non-social) and manner of disappearance (occlusion or implosion). Visual tracking was measured with a TOBII eye tracking system.Results: The principal dependent measure was the time difference between the reappearance of the object and the first fixation to the far side of the occluding surface. If the first fixation appeared within200ms of the reappearance of the object, we scored the trial as predictive. Preliminary results reveal that predictive tracking increased as a function of age and was more frequent in the occlusion condition. In addition, predictive tracking was more frequent at both ages to the animated cartoon character than to the rolling ball.Conclusion: These results support our hypothesis that infants are more proficient at predictively tracking a social than a non-social stimulus suggesting that the representation of social stimuli differs from the representation of non-social stimuli.