Abstract
If the opposite moving dots were located sparse enough, we can see the global two planes moving opposite directions. This perception is called motion transparency. We conducted three experiments on the development of the motion perception for total 112 3- to 5- month-olds infants using these opposite moving dots. Qian, et al. (1994) showed that opposite moving dots located within 0.4 deg did not produce the percept of the two global planes. We used this paired dot stimuli as a distracter and the transparent motion as a target. In Exp 1, all stimuli were consisted of 90 moving dots, and in target stimuli the distances between opposite moving dots were varied from trial to trial. The target and the distracter were presented simultaneously side by side. The percentage of the time to look at the target motions were measured based on the forced-choice preferential looking method (Teller, 1979). Results showed that 4- and 5-month-old infants showed the preference to the targets but not 3-month-olds. These results suggest that the preference to the motion transparency emerges at 4-months. In Exp 2, we examined the infants' preference to the target in small number of dots. In this experiment, we used three kinds of stimuli (2, 4 and 6 dots moving opposite directions). Results showed that 4- and 5-month-old infants did not looked at the target significantly in all conditions. These results suggest that the preference to the target motions decreases according to the number of the dots. In Exp 3, we used the longer traveling length of the dots and the longer distance between opposite moving dots. Results showed that all age group looked at the target motions in all stimulus conditions. These results suggest that the perception of motion transparency based on the global motion cue emerges at 4-month-olds (Exp 1 and 2) and the traveling length of the dots promote the perception of motion transparency (Exp 3).