Abstract
Previous studies found that even 2-month-olds can integrate local motion signals into a coherent motion (Manny & Fern, 1990; Dobkins et al., 2004). However, not all the motion signals should be integrated. Previous psychophysical studies showed that human visual system makes use of form information such as occlusion to determine whether local motion signals should be integrated or segregated (McDermott et al., 2001). Using the diamond display developed by McDermott et al. (2001), we examined the effect of occlusion on motion integration in infants.
Infants were familiarized with the diamond stimulus either in the occlusion condition or in the bar condition. After familiarization, they were shown two types of test displays; global motion (GM) test display and local motion (LM) test display. Both of the test displays were composed of four moving dots. In the GM test display, the movement of four dots simulated the coherent motion of the diamond behind the occluders. In the LM test display, the movement of four dots simulated the local motion of the line segments (local motion).
We found that only 5- to 8-month-olds showed significantly greater preference for the LM test display in the occlusion condition than in the bar condition. These results suggest that 5- to 8-month-olds perceived motion to be more coherent in the occlusion condition than in the bar condition. The results from control experiment suggest that the effect of occlusion depend on the global completion of occluded diamond in infants as well as in adults.
This research was supported by RISTEX Japan Science Technology Agency, and a Grant-in-Aid for scientific research (15500172) from JSPS.