Head movements are correlated with other measures of visual attention at smaller spatial scales

Overt visual attention is traditionally studied by recording eye movements under head-fixed viewing conditions. However, during natural visual exploration, both head and eye movements can be used to redirect gaze to new points of interest. In order to better understand the role of head movements in this process, we recorded head movements while subjects explored a set of complex images from five different categories in a virtual reality environment. We found image-category specific differences in head movements, as quantified by the number and duration of head 'fixations' (periods of maintained head orientation) as well as the amplitude of head movements. We compared head fixations with several other behavioral measures of attentional selection and with a computational model of bottom-up saliency, using the same set of complex scenes in all experiments. Results show significant positive correlation between head fixations and all other measures of attentional deployment, suggesting that head movements are a readily measurable indicator of overt selective attention at a spatial scale exceeding that of eye movements.