Visual motion is processed by neurons in primary visual cortex that are sensitive to the spatial orientation and speed of the visual input. Many models of local velocity computation are based on a second stage that pools the outputs of first-stage neurons selective for different orientations, but the nature of this pooling remains controversial. In a psychophysical detection experiment, we find that human subjects show near-perfect summation of image energy when it is distributed uniformly across all orientations, but poor summation when it is concentrated in specific orientation bands. The data are consistent with a model that integrates uniformly over all orientations, even when this strategy is sub-optimal.