Padrões estatísticos do movimento ocular na busca visual

Abstract

Since the pioneering work of Emile Javal about reading in 1879 (E. Javal, 2010), the movement of the eyes has been the subject of intensive research as a way to elucidate inner mechanisms of cognitive processes that are closely related with vision (A. L. Yarbus, 1967). Among others, a cognitive task that is rather frequent in our daily life is the visual search of hidden objects. Here we investigate through eye-tracker experiments, the statistical properties associated with the search of target images embedded in a landscape of distractors. Our results show that the twofold process of eye movement, composed of sequences of small jumps (fixation) intercalated by fewer longer jumps (saccades), displays characteristic statistical signatures. More precisely, while the saccadic jumps follow a lognormal distribution of distances, which is typical of multiplicative processes, the lengths r of the smaller steps in the fixation trajectories are consistent with a powerlaw distribution, P(r) ∼ r −α , where α ≈ 3.1. Our findings corroborate previous complex behaviour attributes observed for visual searching as a cognitive task.