Fixation durations in scene viewing: Modeling the effects of local image features, oculomotor parameters, and task

Antje Nuthmann

doi:10.3758/s13423-016-1124-4

Abstract

Scene perception requires the orchestration of image- and task-related processes with oculomotor constraints. The present study was designed to investigate how these factors influence how long the eyes remain fixated on a given location. Linear mixed models (LMMs) were used to test whether local image statistics (including luminance, luminance contrast, edge density, visual clutter, and the number of homogeneous segments), calculated for 1° circular regions around fixation locations, modulate fixation durations, and how these effects depend on task-related control. Fixation durations and locations were recorded from 72 participants, each viewing 135 scenes under three different viewing instructions (memorization, preference judgment, and search). Along with the image-related predictors, the LMMs simultaneously considered a number of oculomotor and spatiotemporal covariates, including the amplitudes of the previous and next saccades, and viewing time. As a key finding, the local image features around the current fixation predicted this fixation’s duration. For instance, greater luminance was associated with shorter fixation durations. Such immediacy effects were found for all three viewing tasks. Moreover, in the memorization and preference tasks, some evidence for successor effects emerged, such that some image characteristics of the upcoming location influenced how long the eyes stayed at the current location. In contrast, in the search task, scene processing was not distributed across fixation durations within the visual span. The LMM-based framework of analysis, applied to the control of fixation durations in scenes, suggests important constraints for models of scene perception and search, and for visual attention in general.

Highlights

Human vision during natural scene perception is an active process whereby observers selectively seek out information in the visual environment relevant to perceptual, cognitive, or behavioral goals (Findlay & Gilchrist, 2003)
Does the luminance in a limited spatial region around the current fixation modulate this fixation’s duration? In addition, the analyses focused on whether scene processing is distributed across fixation durations within the visual span, an idea first proposed in research on eye movements in reading (e.g., Engbert, Nuthmann, Richter, & Kliegl, 2005; Kliegl, Nuthmann, & Engbert, 2006; Schad, Nuthmann, & Engbert, 2010)
These models are referred to as the full Linear mixed models (LMMs); in technical terms, they correspond to the final zcpLMMs derived above

Summary

Introduction

Human vision during natural scene perception is an active process whereby observers selectively seek out information in the visual environment relevant to perceptual, cognitive, or behavioral goals (Findlay & Gilchrist, 2003). We move our eyes about three times each second via rapid eye movements (saccades) to reorient the fovea around the scene. Gaze position is relatively stable, and during these periods of fixation, visual information is acquired (for reviews, see Henderson, 2003; Rayner, 2009). The visuo-oculomotor system is required to make spatial decisions regarding the target location for the saccade (i.e., the Bwhere^ decision), as well as temporal decisions regarding the time at which to terminate the current fixation (i.e., the Bwhen^ decision). The present article is concerned with the factors that influence the Bwhen^ decisions about fixation durations. I investigate how these influences depend on task-related control

Objectives

Results

Conclusion