Garner-Interference in Skilled Right-Handed Grasping is Possible.

According to the Perception-Action-Model (PAM), the human visual cortex consists of the ventral vision-for-perception and the dorsal vision-for-action streams. Performance decrements with increasing variation of nominally task-irrelevant stimulus features (Garner-Interference) was suggested as an empirical tool for identifying contributions of these streams: vision-for-perception, but not visionfor-action, should suffer from Garner-Interference, but inconsistencies in this argument were revealed by several studies. We here used a new manipulation to induce Garner-Interference in a dorsal task: The stimulus objects did not differ in their lengths but in the side to which they were weighted. In Experiment 1, Garner-Interference was found in a ventral perceptual judgment task. Notably, we did also find Garner-Interference in skilled right-handed grasping in Experiment 2. These findings suggest that the presence or absence of Garner-Interference does not consistently index the contribution of different processing streams for perception and action, but the coprocessing of nominally task-irrelevant stimulus features in general, be it for perception of action.