Vison Research Vol. 32, No. 6, pp. 1137-1141, 1992

Lateral Motion Bias Associated with Reading Direction

Kazunori Morikawa, Michael K. McBeath

We found that when Americans view ambiguous lateral long-range apparent motion, they exhibit a robust bias to experience leftward movement. In successive experiments, right-handers and left-handers, and left-side drivers from Japan equally manifested this leftward bias. However, bilingual viewers whose first language reads from right to left exhibited no lateral bias. Furthermore, the bilingual sample produced a significant correlation between exposure to English and extent of leftward motion bias. The finding provide strong evidence that reading habits can influence directionality in motion perception.

FIGURE 1. Stimuli used in the experiments. (a) The test condition. Because the second frame is spatially shifted by exactly a cycle from the first frame, we refer to it as the neutral-shift condition. (b) The left-shift condition. (c) The right-shift condition. In the latter two conditions the second frame is shifted in the specified direction by a quarter cycle.

FIGURE 2. Magnitude of bias was defined as number of rightward responses minus number of leftward responses for each subject. Each bar indicates the mean of 8 subjects. Negative scores indicate leftward bias. Error bars equal +/-1 SEM. The native language of the top two groups is English. Left side drivers are native Japanese whose first language reads left to right. Thus, the top three groups also represent left-to-right readers as opposed to the fourth group whose first language reads right to left. The Japanese sample also provides a bilingual control in which both languages read left to right.