One of the unsettled issues in visual search research is whether the search for a conjunction of motion and the other physical feature (e.g. color or shape) is serial or parallel. In the present experiment, the subjects (six undergraduate students) were instructed to search for a target defined by color, shape, motion, or combinations of the two out of these three features, and the reaction time was measured. The slopes of the regression (number of items in the display vs. reaction time) are the largest for a target defined by a conjunction of color and shape, the smallest for a target defined by one feature, and intermediate for a moving conjunctive target. These results are consistent with those of McLeod and colleagues (1988, 1991) which suggest that a specific visual subsystem operates as a movement filter.
