The role of stimulus factors in making categorical and coordinate spatial judgments

We report three experiments which investigate the lateralization of categor ical and coordinate processing. In all experiments, participants judged the position of a dot relative to a line. We manipulated display luminance (co ntrolling for contrast), polarity (black-on-white versus white-on-black dis plays), and exposure duration (100, 150, and 200 ms). The results showed a left visual field-right hemisphere advantage for coordinate judgments, but only under highly prescribed conditions. We argue that stimulus and procedu ral factors are critical in determining the hemisphere by task interaction, (C) 1999 Academic Press.