Walking reveals trunk orientation bias for visual attention.

Our trunks influence where we perform actions in space. Thus, trunk direction may define a region of spacethat is accorded special treatment by the attention system. We investigated conditions under which a trunk orientation bias for attention might be relevant for healthy adults. Three experiments compared visual detection performance for participants standing and walking on a treadmill. Together, the experiments disambiguate the relative contributions of motor activity, motor load, and cognitive load on trunk orientation biases. In Experiment 1, trunk orientation biases (i.e., faster target detection for targets in front of the body midline) were observed in both forward and sideways walking conditions, but not in standing conditions. In Experiment 2, we ruled out the notion that the trunk orientation bias arose from increased motor activity; in fact, the bias was greatest when participants walked at an unusually slow pace. In Experiment 3, we directly compared motor load with cognitive load in a dual-task paradigm; cognitive load influenced overall performance speed, but only motor load produced trunk orientationbias. These results suggest that a trunk orientation bias emerges during walking and motor load conditions.