Individuals exhibit idiosyncratic eye-movement behavior profiles across tasks

Abstract

The purpose of this study was to examine individual differences in eye-movement behavior. Six metrics (Fixation Rate, Duration, and Size; Saccade Amplitude; Micro-Saccade Rate and Amplitude) were used to measure individuals' eye-movement behavior profiles (EmBP). We replicate previous research (Andrews & Coppola, 1999; Castelhano & Henderson, 2008) by finding consistent individual differences in fixation duration and saccade amplitude across tasks, and present new findings of stable idiosyncrasies in measures of fixational eye-movement (Fixation Size, Micro-Saccade Rate and Amplitude). Moreover, we observed consistent inter-metric correlations across tasks (e.g., individuals that exhibited relatively high Fixation Rates also presented relative low Micro-Saccade Rates and relatively high Micro-Saccade Amplitudes). Factor Analysis linked the six EmBP metrics together with a single factor, which we speculate might be related to the operational effectiveness of the attentional system, given that individual factor scores were correlated with scores on a self-report measure of attentional function. Normal subjects with relatively high scores on this attention-deficit measure exhibited relatively frequent fixations of short duration and large spatial extent, and relatively infrequent micro-saccades of large amplitude. This EmBP is similar to a general pattern of eye-movement behavior observed with ADHD individuals - difficulty controlling eye movements, maintaining fixation, and inhibiting intrusive saccades. Results of this study indicate that normal individuals exhibit idiosyncratic EmBPs that are quite stable across tasks and are related to attentional ability.