Spatial biases in viewing behavior

Abstract

Viewing behavior exhibits temporal and spatial structure that is independent of stimulus content and task goals. One example of such structure is horizontal biases, which are likely rooted in left-right asymmetries of the visual and attentional systems. Here, we studied the existence, extent, and mechanisms of this bias. Left- and right-handed subjects explored scenes from different image categories, presented in original and mirrored versions. We also varied the spatial spectral content of the images and the timing of stimulus onset. We found a marked leftward bias at the start of exploration that was independent of image category. This left bias was followed by a weak bias to the right that persisted for several seconds. This asymmetry was found in the majority of right-handers but not in left-handers. Neither low- nor high-pass filtering of the stimuli influenced the bias. This argues against mechanisms related to the hemispheric segregation of global versus local visual processing. Introducing a delay in stimulus onset after offset of a central fixation spot also had no influence. The bias was present even when stimuli were presented continuously and without any requirement to fixate, associated to both fixation- and saccade-contingent image changes. This suggests the bias is not caused by structural asymmetries in fixation control. Instead the pervasive horizontal bias is compatible with known asymmetries of higher-level attentional areas related to the detection of novel events.

High spatial validity is not sufficient to elicit voluntary shifts of attention

“…However, a recent attentional model introduced by Takio, Koivisto, and Hämäläinen (2014) suggests that a right visual field advantage occurs in both linguistic and nonlinguistic spatial attention tasks due to lateralized processing of linguistic stimuli, as well as asymmetries in attentional, bottom-up neural processes (see also Robertson, 2004). This account can be further distinguished from other higher level, cultural accounts, which suggest a left-to-right attentional bias in a variety of different paradigms, though the interpretations of this bias have been somewhat mixed (see Ossandon, Onat, & Konig, 2014, for a review). One interpretation suggests that visuospatial asymmetries along the horizontal axis are critically modulated by directional oculomotor routines associated with reading and writing.…”

The elephant in the room: Inconsistency in scene viewing and representation.

“…It has indeed been shown that viewers have a leftward bias in starting scene inspection (Dickinson & Intraub, 2009;Foulsham & Kingstone, 2010;Nuthmann & Matthias, 2014;Ossandón, Onat & König, 2014). In the "original" (evaluated) orientation, two scenes had both objects in the left half, two had both objects in the right half, while the remaining had one object in each side.…”

Flipping the stimulus: Effects on scanpath coherence?

“…Compared with other studies documenting asymmetries in left-right fixation distribution (Nuthmann & Matthias, 2014;Ossandón et al, 2014), we used a dynamic task in which the repeated presentation was concealed. Therefore, participants had to sustain their attention and adjust their eye movements accordingly over the course of the trial, and they had smaller freedom to look at the remaining parts of the display, which were not relevant for the task.…”

“…In the case of MOT, if people track a group of targets as a single object (Yantis, 1992), we should expect no left-right difference, since the optimal viewing position is found at the center of the perceived object, with no lateral bias (Foulsham & Kingstone, 2010). Conversely, others have reported a preference for early fixations to the left part of the scene (Dickinson & Intraub, 2009;Foulsham, Gray, Nasiopoulos, & Kingstone;2013;Nuthmann & Matthias, 2014;Ossandón, Onat, & König, 2014). This bias is often discussed with respect to Bpseudoneglect^: a leftward bias in the line-bisection task in healthy humans (Bowers & Heilman, 1980;Jewell & McCourt;2000).…”

“…The left-right asymmetries in fixation patterns happen within a few fixations at the beginning of a trial and later disappear (Nuthmann & Matthias, 2014;Ossandón et al, 2014). In a dynamic task like MOT, it is an open question whether a left-right asymmetry would be observed.…”