Riku Umekawa¹ (), So Kanazawa², Masami K. Yamaguchi¹; ¹Chuo University, ²Japan Women's University

We investigated whether adaptation from implied motion (IM) was transferred to real motion by using optokinetic nystagmus (OKN) in infancy. We examined whether viewing a series of images depicting motion altered the OKN response to Random dot kinematogram (RDK) in infants. The RDK were presented 10 times in pretest, followed by 10 trials of IM adaptation and test during which we measured infants’ OKN responses. The coherence of RDK was 50% in Experiment 1 and 80% in Experiment 2. In the pretest, the signal dots of RDK moved left or right. In IM adaptation, 10 randomly selected leftward (or rightward) IM images were presented at the center of the monitor at a rate of 600 ms per image (with no ISI). During test, RDK was presented immediately following the last IM image. The test RDK and IM images were in the same directions. An observer, who was blind to the direction of motion, judged the direction of OKN. We calculated the number of matches of OKN responses of each RDK direction as a “match ratio of OKN.” Forty from five to eight months infants in Experiment 1 and sixty from three to eight months infants in Experiment 2 participated. We conducted a two-way mixed ANOVA, with age group as between-participant factors and adaptation (pretest and test) as within-participant factors. In Experiment 1 we found that IM adaptation reduced the OKN response to RDK direction for 7-to-8-month-olds, but not for 5-to-6-month-olds. In Experiment 2 we found that IM adaptation reduced the OKN response to RDK direction for all infants. That is, we found that around these ages, OKN responses to RDK was altered by viewing a series of images depicting motion. These results suggest that 7- to 8-month-old infants were be able to detect the motion information in static IM images.