Effects of spatial frequency and attention on pupillary response.

Research has shown that the pupil responds differently depending on the spatial frequency of the gazing stimulus. In this study, we examined the effects of spatial- and object-based attention on pupillary response as a function of spatial frequency using grating stimuli and filtered natural images by manipulating the participants' attentional state. Furthermore, we aimed to obtain the pupillary response to spatial frequency accurately by reducing the contamination of unintended spatial frequency components in the stimulus by using gratings with a Gabor envelope. We revealed that all stimuli could elicit large pupil constriction for an intermediate range (2-8 c/d) of spatial frequency and that both spatial- and object-based attention modulate the pupillary response function to spatial frequency. These facts may enhance Human Computer Interaction design to use people's attentional state.