A Computational Dual-Process Model of Fixation-Duration Control in Natural Scene Viewing

Abstract

Research on eye-movement control during natural scene viewing has investigated the degree to which the duration of individual fixations can be immediately adjusted to ongoing visual-cognitive processing demands. Results from several studies using the fixation-contingent scene quality paradigm suggest that the timing of fixations adapts to stimulus changes that occur on a fixation-to-fixation basis. Analysis of fixation-duration distributions has revealed that saccade-contingent degradations and enhancements of the scene stimulus have two qualitatively distinct types of influence. The surprise effect begins early in a fixation and is tied to surprising visual events such as unexpected stimulus changes. The encoding effect is tied to difficulties in visual-cognitive processing and occurs relatively late within a fixation. Here, we formalize an existing descriptive account of these two effects (referred to as the dual-process account) by using stochastic simulations. In the computational model, surprise and encoding related influences are implemented as time-dependent changes in the rate at which saccade timing and programming are completed during critical fixations. The model was tested on data from two experiments in which the luminance of the scene image was either decreased or increased during selected critical fixations (Walshe & Nuthmann, Vision Research, 100, 38–46 2014). A counterfactual method was used to remove model components and to identify their specific influence on the fixation_duration distributions. The results suggest that the computational dual-process model provides a good account for the data from the luminance-change studies. We describe how the simulations can be generalized to explain a diverse set of experimental results.

An updating-based working memory load alters the dynamics of eye movements but not their spatial extent during free viewing of natural scenes

“…Regarding fixation durations, eye movements have been described using a mixed-control account: some eye movements are subject to direct control , such that processing of information obtained from a specific fixation occurs fast enough to influence the timing of subsequent saccades (and thus the length of the present fixation). Conversely, others are subject to indirect control , such that fixation duration is relatively invariant to the properties of the fixated stimulus (Henderson & Pierce, 2008 ; Nuthmann, 2017 ; Walshe & Nuthmann, 2021 ). A unifying characteristic of eye movements subject to direct control is that they are linked to circumstances where acquisition of information is more challenging: when a stimulus percept is degraded (Glaholt et al, 2014 ; Henderson et al, 2013 ) or an unfamiliar or unexpected word is encountered when reading (Kliegl et al, 2006 ), fixation durations increase.…”

“…Indeed, some accounts of fixation duration in scene viewing (Nuthmann et al, 2010 ; Trukenbrod & Engbert, 2014 ) associate ‘difficulties’ in visual and cognitive processing at a specific fixation with slower saccade initiation, or even cancellation of planned saccades. Furthermore, Walshe and Nuthmann ( 2021 ) propose an encoding modulation that operates when such difficulties in stimulus processing are encountered, which increases the proportion of long fixations concentrated at the rightward tail of the distribution of fixation durations.…”

“…If attentional breadth does broaden under higher load due to a failure of selective control, what might this impairment of attentional control under higher working memory load look like if also present for exploratory behaviour? Consistent with a decrease in efficiency of processes dependent on attentional control such as saccade planning and execution (Nuthmann et al, 2010 ; Trukenbrod & Engbert, 2014 ; Walshe & Nuthmann, 2021 ), operating under a higher working memory load may decrease the amplitude of saccades and hence shorten scan paths, while also increasing fixation durations. In turn, this decreases exploration of areas of the stimulus that are further out from the centre, contracting exploratory breadth.…”

I’m not sure that curve means what you think it means: Toward a [more] realistic understanding of the role of eye-movement generation in the Visual World Paradigm

“…Similarly, the analysis of earlier empirical data showed no difference between the durations of fixations to competitors and other objects; however there could be a short-lived difference during the brief period when the competitor is more active (see McMurray, Aslin, et al, 2008, for an example). A more comprehensive understanding of duration could also improve these models like (c.f., Walshe & Nuthmann, 2021).…”