Pseudoneglect during object search in naturalistic scenes

Abstract

Pseudoneglect, that is the tendency to pay more attention to the left side of space, is typically assessed with paper-and-pencil tasks, particularly line bisection. In the present study, we used an everyday task with more complex stimuli. Subjects’ task was to look for pre-specified objects in images of real-world scenes. In half of the scenes, the search object was located on the left side of the image (L-target); in the other half of the scenes, the target was on the right side (R-target). To control for left–right differences in the composition of the scenes, half of the scenes were mirrored horizontally. Eye-movement recordings were used to track the course of pseudoneglect on a millisecond timescale. Subjects’ initial eye movements were biased to the left of the scene, but less so for R-targets than for L-targets, indicating that pseudoneglect was modulated by task demands and scene guidance. We further analyzed how horizontal gaze positions changed over time. When the data for L- and R-targets were pooled, the leftward bias lasted, on average, until the first second of the search process came to an end. Even for right-side targets, the gaze data showed an early left-bias, which was compensated by adjustments in the direction and amplitude of later saccades. Importantly, we found that pseudoneglect affected search efficiency by leading to less efficient scan paths and consequently longer search times for R-targets compared with L-targets. It may therefore be prudent to take spatial asymmetries into account when studying visual search in scenes.

Gaze data of 4243 participants shows link between leftward and superior attention biases and age

“…The association between gaze bias and age was found for the first three to seven fixations in the horizontal dimension, and for the first to sixth fixations in the vertical dimension. Interestingly, previous studies have shown that in free viewing, a leftward bias is typically exhibited in these early fixations (Chiffi et al 2021 ; Foulsham et al 2018 ; Hartmann et al 2019 ; Nuthmann and Clark 2023 ; Nuthmann and Matthias 2014 ; Ossandon et al 2014 ). Such a gaze bias shortly after stimulus onset suggests that spatial attention is not biased per se, but that there is a bias in the spatial orienting of attention (as understood based on Petersen and Posner 2012 and Posner 1990 ).…”

“…This leftward bias peaks around the second to third fixation and persists for up to 1.5 s of a trial (Chiffi et al 2021 ; Foulsham et al 2018 ; Hartmann et al 2019 ; Ossandon et al 2014 ). This leftward gaze bias is robust to stimulus content (Ossandon et al 2014 ), viewing distance (Hartmann et al 2019 ), and even task goals such as visual search or memorization (Nuthmann and Clark 2023 ; Nuthmann and Matthias 2014 ; Zelinksy 1996 ). Furthermore, the bias remains present when there is no need to maintain central fixation before image onset, ruling out explanations related to asymmetries in fixation control (Ossandon et al 2014 ).…”

(Micro)saccade-related potentials during face recognition: A study combining EEG, eye-tracking, and deconvolution modeling

“…This bias also manifests itself in eye movements, where the first saccade on a face is often aimed towards the left (Butler et al, 2005;Butler & Harvey, 2006;Hsiao & Cottrell, 2008;Mertens et al, 1993). Notably, however, some of this effect may not be specific to faces, but may reflect a more general tendency to direct the first saccade on complex stimuli towards the left (e.g., for natural scenes see Nuthmann & Clark, 2023;Nuthmann & Matthias, 2014), a phenomenon which has been hypothesized to reflect a relative dominance of right-hemispheric parietal-frontal attention networks ("pseudoneglect"; Bowers & Heilman, 1980). Regardless of the exact cause of this leftward bias, we interestingly observed that it was already present for microsaccades during the prestimulus baseline interval (see Fig.…”