Left Hemisphere Lateralization of Categorical Color Perception among Roman and Arabic Script Readers

So far, the Left Hemisphere (LH) bias in color Categorical Perception (CP) has been related to the linguistic nature of the LH and converging evidence to support this hypothesis has been presented in several studies. As, to date, no evidence of lateralized CP has been shown on right-to-left readers in support of this theory. However, the influence of reading habits to perception has been shown in various studies. This study aimed to investigate the possible effect of habitual scanning on lateralization of color CP, by comparing participants from two languages who vary in their reading direction: right-to-left in Arabic and left-to-right in English. Lateralization of CP was then tested in two groups of Arabic and English. The Arabic group consisted of 35 undergraduate students at King Saud University. The English group consisted of 29 native English-speakers who were undergraduate students of Surrey University. Their ages range from 18 to 30 years. Two tasks were used to test this hypothesis: a visual search task with a reaction time measure; and a target detection task with eye-movement measure. Both samples performed similarly and the pattern of lateralization has been replicated, but this time, it has also been shown that the effect is independent of habitual reading direction. It appears that reading direction has no effect on how color CP is lateralized.