Abstract
The aim of this study was to investigate the validity of Lavie's load theory (Lavie, 2005) from the point of view of cerebral lateralization. In Experiment 1, right-handed participants were asked to discriminate a target letter in a task-relevant letters-array which was presented at a left or right visual-field, while ignoring a letter (distractor) which was presented above or below a central fixation. We manipulated the perceptual load (high/low) of the task-relevant letter-arrays and the compatibility between a target and a distractor. The results showed that the compatibility effect was larger in the low load condition than in the high load condition irrespective of visual-field, which supported the load theory. The second experiment was the same as Experiment 1, except that a triangle, the high-load letter-array and the distractor were simultaneously presented. We set up two object conditions; within-object and across-object conditions. In the former condition, the letter-array and the distractor was presented within the triangle. In the latter, only the letter-array was presented within the triangle and the distractor was presented outside the triangle. The results showed that in the left visual-field condition, the compatibility effect was observed only in the within-object condition, not in the across-object condition, whereas in the right visual-field condition, it was observed in both the conditions. These results suggested that selective attention is modulated by cerebral dominance for letter search.
