Abstract
In object substitute masking (OSM), target perception is impaired when a target is briefly presented with a surrounding mask that remains on-screen after the target disappears. Several studies suggest that this phenomenon arises from a disruption of recurrent processing. Here, we investigated OSM in 3–8-month-old infants using a preferential looking paradigm with face stimuli. A face and three distracters were presented for 250 ms, where the face was surrounded by four dots (mask). In the delayed-mask offset condition (masked condition), the mask remained on the screen for 250 ms after the target disappeared. In the simultaneous-offset condition (unmasked condition), the target and mask disappeared simultaneously. The stimulus sequence was repeated for 11 s on each trial. The two conditions were presented alternately and were repeated five times. If OSM occurs, faces cannot be perceived in the masked condition, and looking times for the stimulus array would be longer in the unmasked condition. The results showed that 7–8-month-old infants looked longer in the unmasked condition, while 3–6-month-old infants did not, suggesting that OSM only occurs in older infants. To further test the absence of OSM in younger infants, we conducted an additional experiment to compare the masked condition with a no-face condition. The no-face condition was same as the unmasked condition, except that the face was replaced by a blank. If OSM does not occur, looking time would be longer in the masked condition. Infants at 3–6 months showed longer looking time in the masked condition, while 7–8-month-old infants did not. These results indicate that infants under 7 months are immune to OSM, and they can perceive faces that older infants cannot because of masking. Our findings suggest that recurrent processing is immature in early infancy, and they can perceive objects even without mature recurrent processing.