Purchase this article with an account.
Natalya Shelchkova, Christie Tang, Michele Rucci, Martina Poletti; The role of small eye movements in spatial exploration. Journal of Vision 2017;17(10):1159. doi: 10.1167/17.10.1159.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Spatial exploration occurs at multiple scales. At the relatively large scale at which it is commonly investigated, humans use saccades to explore a scene and examine objects of interest by means of the high-acuity foveola. Yet, many everyday tasks require exploration at a finer scale, as objects are often viewed from a distance and tasks that require analysis of fine details often occur. Previous research has shown that, contrary to common intuition, simply placing the attended stimulus within the foveola is not sufficient to perform well in high-acuity tasks, and that small eye movements play important roles. Here we examine the exploratory role of fixational eye movements in a common high-acuity task, the evaluation of facial expression. Human observers were asked to judge facial expressions when faces covered approximately the size of the foveola (1 deg diameter), as it normally happens when looking at a person from a distance larger than 13 meters. A high-resolution Dual Purkinje Image eyetracker was used to record eye movements and was coupled with a custom gaze-contingent calibration procedure that has been shown to improve gaze localization by approximately one order of magnitude over standard methods. We show that spatial exploration of foveal stimuli follows strategies very similar to those used to explore broader scenes. Visual exploration is primarily executed by means of precisely controlled microsaccades (average amplitude: 14 arcmin), which center gaze on salient and task-relevant regions. Both bottom-up and top-down factors influence the pattern of microsaccades; in the presence of the same visual stimulation exploration changes based on the demands of the task. These results indicate that observers do not simply fixate on foveated stimuli, but actively explore them. This level of oculomotor control is necessary to operate effectively in tasks that require high-acuity vision and implies the existence of high-resolution saliency maps.
Meeting abstract presented at VSS 2017
This PDF is available to Subscribers Only