Exploration and Exploitation in Natural Viewing Behavior

Ricardo Ramos Gameiro,Sontje Nordholt,Kai Kaspar,Peter König,Sabine U König

doi:10.1038/s41598-017-02526-1

Abstract

Many eye-tracking studies investigate visual behavior with a focus on image features and the semantic content of a scene. A wealth of results on these aspects is available, and our understanding of the decision process where to look has reached a mature stage. However, the temporal aspect, whether to stay and further scrutinize a region (exploitation) or to move on and explore image regions that were yet not in the focus of attention (exploration) is less well understood. Here, we investigate the trade-off between these two processes across stimuli with varying properties and sizes. In a free viewing task, we examined gaze parameters in humans, involving the central tendency, entropy, saccadic amplitudes, number of fixations and duration of fixations. The results revealed that the central tendency and entropy scaled with stimulus size. The mean saccadic amplitudes showed a linear increase that originated from an interaction between the distribution of saccades and the spatial bias. Further, larger images led to spatially more extensive sampling as indicated by a higher number of fixations at the expense of reduced fixation durations. These results demonstrate a profound shift from exploitation to exploration as an adaptation of main gaze parameters with increasing image size.

Highlights

Vision is the key modality by which humans interact with the environment
Our first hypothesis stated that visual exploration increases with increasing image size, which is reflected by a reduction of the central tendency and an increase of entropy
With respect to the horizontal direction, we found a main effect of image size reflecting a reduction of the central tendency with increasing image size

Summary

Introduction

Vision is the key modality by which humans interact with the environment. our processing capacity is limited regarding attention[1,2,3,4,5]. The time spent at a fixated location (i.e., fixation duration) reflects the degree of in-depth processing of what is observed and characterizes the exploitation aspect[14,15,16]. While scanning a scene, overt attention in visual behavior consists of a continuous interplay between exploration and exploitation. Vision research has identified several factors that influence eye movement behavior. Top-down factors cover specific personal interests[33] that may be different depending on the current task performed by the observer[34, 35] Overall, such top-down factors play a major role in viewing behavior and can explain a large part of the variance in eye movements. Bottom-up factors comprise the properties of the stimulus that influences the selection of fixation locations. Models based on the concept of a salience map that incorporates such basic image properties can predict human visual www.nature.com/scientificreports/

Results

Discussion

Conclusion