O hand, where art thou? Mapping hand location across the visual field during common activities.

Humans employ visually-guided actions during a myriad of daily activities. These ubiquitous but precise manual actions rely on synergistic work between eye and hand movements. During this close cooperation between hands and eyes, the hands persist in sight in a way which is unevenly distributed across our visual field. One common assertion is that most hand actions occur in the lower visual field (LVF) because the arms are anatomically lower than the head, and objects typically rest on waist-high table surfaces. While experimental work has shown that humans are more efficient at reaching for and grasping targets located below their visual midline (Goodale and Danckert, Exp Brain Res 137:303-308, 2001), there is almost no empirical data detailing where the hands lie in the visual fields during natural hand actions. To build a comprehensive picture of hand location during natural visually guided manual actions, we analyzed data from a large-scale open-access dataset containing 100 h of non-scripted manual object interactions during domestic kitchen tasks filmed from a head-mounted camera. We found a clear vertical visual asymmetry with hands located in the lower visual scene (LVS) in more than 70% of image frames, particularly in ipsilateral space. These findings provide the first direct evidence for the established assumption that hands spend more time in the lower than in the upper visual field (UVF). Further work is required to determine whether this LVF asymmetry differs across the lifespan, in different professions, and in clinical populations.