Influence of stimuli factors and attention on the transition from global to local dominance

Abstract

Two experiments are reported which examined the effects of size in both certainty and uncertainty conditions, and their possible interaction with exposure duration in determining processing dominance. In Experiment 1, the size of the stimuli was presented randomly within each block of trials (size-uncertainty condition). In Experiment 2, the size of the stimuli was presented blocked (size-certainty condition). In both experiments, hierarchical stimuli, that is to say, global letters composed by few relatively large local elements with large differences in eccentricity between the global and local levels (H´s and A´s compound letters) were presented under two conditions of exposure duration (10 and 200 msec. The results showed local dominance in the large-sized condition in both Experiment 1 and 2. However, attentional factors and exposure duration of stimuli modulated the magnitude of the effects: The advantage effect was enhanced at short exposure duration whereas the magnitude of the interference effect was enhanced in size-uncertainty conditions.