Influence of initial fixation position in scene viewing

TL;DR

This study examines how the initial fixation point influences subsequent eye movements during scene viewing, revealing transient biases and overshoot behaviors, and suggests inhibitory tagging as a mechanism for scanpath planning.

Contribution

It provides new insights into the dynamics of scanpaths influenced by initial fixation positions and introduces inhibitory tagging as a plausible underlying mechanism.

Findings

Initial fixation position causes long-lasting biases in scanpaths.

Participants tend to overshoot to the opposite side of the initial fixation.

Inhibitory tagging may explain the observed scanpath dynamics.

Abstract

During scene perception our eyes generate complex sequences of fixations. Predictors of fixation locations are bottom-up factors like luminance contrast, top-down factors like viewing instruction, and systematic biases like the tendency to place fixations near the center of an image. However, comparatively little is known about the dynamics of scanpaths after experimental manipulation of specific fixation locations. Here we investigate the influence of initial fixation position on subsequent eye-movement behavior on an image. We presented 64 colored photographs to participants who started their scanpaths from one of two experimentally controlled positions in the right or left part of an image. Additionally, we computed the images' saliency maps and classified them as balanced images or images with high saliency values on either the left or right side of a picture. As a result of the starting point manipulation, we found long transients of mean fixation position and a tendency to overshoot to the image side opposite to the starting position. Possible mechanisms for the generation of this overshoot were investigated using numerical simulations of statistical and dynamical models. We conclude that inhibitory tagging is a viable mechanism for dynamical planning of scanpaths.