Global attention facilitates the planning, but not execution of goal-directed reaches

Abstract

In daily life, humans interact with multiple objects in complex environments. A large body of literature demonstrates that target selection is biased toward recently attended features, such that reaches are faster and trajectory curvature is reduced when target features (i.e., color) are repeated (priming of pop-out). In the real world, however, objects are comprised of several features-some of which may be more suitable for action than others. When fetching a mug from the cupboard, for example, attention not only has to be allocated to the object, but also the handle. To date, no study has investigated the impact of hierarchical feature organization on target selection for action. Here, we employed a color-oddity search task in which targets were Pac-men (i.e., a circle with a triangle cut out) oriented to be either consistent or inconsistent with the percept of a global Kanizsa triangle. We found that reaches were initiated faster when a task-irrelevant illusory figure was present independent of color repetition. Additionally, consistent with priming of pop-out, both reach planning and execution were facilitated when local target colors were repeated, regardless of whether a global figure was present. We also demonstrated that figures defined by illusory, but not real contours, afforded an early target selection benefit. In sum, these findings suggest that when local targets are perceptually grouped to form an illusory surface, attention quickly spreads across the global figure and facilitates the early stage of reach planning, but not execution. In contrast, local color priming is evident throughout goal-directed reaching.

Figure 1

A sample sequence of trials from Experiment 1. Participants pointed to the uniquely colored target. On Figure (grouped) trials, the Pac-men targets were oriented to be consistent with the percept of three circles occluded by triangle that matched the color of the background. On nonfigure (ungrouped) trials, the Pac-men targets were rotated 180° outward according to their center of gravity (see Methods) so that no illusory triangle was present in the display.

Figure 2

Results of Experiment 1. Reaches were initiated faster for Figure trials compared to No Figure trials (top). Color priming was observed for all three measures. Error bars represent 95% confidence intervals for the within-subject design (Loftus & Masson, 1994).

Figure 3

Effects of Figure repetition in Experiment 1. The line with circles illustrates the initiation latencies for repeated Figure presentations averaged across subjects. Error bars represent 95% confidence intervals for the within-subjects design (Loftus & Masson, 1994).

Figure 4

Stimuli used in the second experiment. An illusory triangle was always present and could be oriented upward (left) or downward (right).

Figure 5

Results of Experiment 2. Changing the orientation of the global Figure across trials had no impact on initiation latency (top), movement time (middle), or curvature (bottom). Color priming was observed for all three measures. Error bars represent 95% confidence intervals for the within-subjects design (Loftus & Masson, 1994).

Figure 6

Stimuli used in the third experiment. Pac-men targets give rise to the percept of a modally completed triangle (left). Pac-men surrounded by a circle support the percept of an amodally completed triangle behind three circular apertures (middle). A triangle defined by a real contour occludes three circular targets (right).

Figure 7

Results of Experiment 3. Reaches were initiated faster for modal and amodal trials compared to real triangle trials, and a main effect of target color was observed (top). Color priming was also observed for movement time (middle) and curvature (bottom). Error bars represent 95% confidence intervals for the within-subject design (Loftus & Masson, 1994).