Abstract
Neurons in different cortical visual areas respond to different visual attributes with different latencies. How does this affect our actions? We compared the latencies of adjustments to hand movements directed towards targets defined by luminance, size, orientation, color, shape and texture. Participants moved their hand as quickly as possible to a visual target that was accompanied by two reference objects. In some trials, the target and one of the references changed location at the onset of the hand's movement. We determined the latency to correct the movement of the hand in the direction of the new target location. It is reasonable to expect the latency to depend both on the attribute in question and on how conspicuous the distinction is within the attribute. For luminance-defined targets we found faster responses with less variability in latency when it was easy to distinguish the target object from the reference objects, than when it was difficult to do so. By considering the relationship between changes in response latency and variability that we found for responding to various differences in luminance, we show that responses for the attributes orientation, luminance and size are fundamentally faster than for color, form and texture. The latency of the latter responses is longer although the variability in latency suggests that the distinction is equally difficult. This dichotomy within the attributes is in accordance with a dorsal-ventral distinction of visual processing in the brain, whereby spatial attributes that are likely to be relevant for guiding our actions (orientation and size) are processed faster than other attributes that are more likely to be relevant for recognizing the object (color, shape and texture).