The relationship between vertical stimulation and horizontal attentional asymmetries

Abstract

The original aim was to examine the effect of perceived distance, induced by the Ponzo illusion, on left/right asymmetries for line bisection. In Experiment 1, university students (n = 29) made left/right bisection judgements for lines presented in the lower or upper half of the screen against backgrounds of the Ponzo stimuli, or a baseline. While the Ponzo illusion had relatively little effect on line bisection, elevation in the baseline condition had a strong effect, whereby the leftward bias was increased for upper lines. Experiment 2 (n = 17) eliminated the effect of elevation by presenting the line in the middle and moving the Ponzo stimuli relative to the line. Despite this change, the leftward bias was still stronger in the upper condition in the baseline condition. The final experiment (n = 17) investigated whether upper/lower visual stimulation, which was irrelevant to the task, affected asymmetries for line bisection. The results revealed that a rectangle presented in the upper half of the screen increased the leftward line bisection bias relative to a baseline and lower stimulation condition. These results corroborate neuroimaging research, showing increased right parietal activation associated with shifts of attention into the upper hemispace. This increased right parietal activation may increase the leftward attentional bias-resulting in a stronger leftward bias for line bisection.

Asymmetries in Distractibility: Left Distractors Improve Reaction Time Performance

“…Leftward attentional asymmetries have been reliably observed for nearly 40 years 15 , 47 . Recent evidence 32 – 34 suggests the strength of leftward biases is influenced by visual field differences in distractibility, such that upper visual field distractors increase the direction of attention to the left. Following from this work, we have demonstrated a significant performance improvement in the presence of irrelevant left side distractors, relative to equivalent distractors presented on the right, specifically when the task is highly demanding.…”

“…Similarly, upper and lower visual field stimuli show differences in their ability to attract attentional resources 24 – 31 , and furthermore, differentially increase distraction 32 – 34 . In general, stimuli in the upper visual field appear to attract more attentional resources, as a result of their higher salience 35 .…”

“…As stimuli in the upper visual field receive more selective attention, and visual search performance is superior in the upper visual field, distractors in the upper visual field might be more distracting. Indeed, prior research examining distractibility in attentional asymmetries has shown that upper visual field distractors preferentially capture attention and also draw attention toward the left side of space 32 – 34 .…”

Unstable world: Recent experience affects spatial perception

“…For example, if participants believed the left segment of the line was longer, the left button was pressed with the index finger on the left hand, with the opposite true for the right. Stimuli presentation and response timing were based on Nicholls et al (2012), with stimuli shown for 500 ms and a response period of 2,000 ms. Participants were instructed to respond only after the prebisected line was removed.…”

Spatial asymmetries (“pseudoneglect”) in free visual exploration—modulation of age and relationship to line bisection

“…Healthy subjects may show a leftward bias in the initial phase of the visual exploration of an image (Dickinson and Intraub 2009;Foulsham 2013;Nuthmann and Matthias 2014;Ossandon et al 2014;Hartmann, 2019). This so-called pseudoneglect has been interpreted as a small, but reliable, asymmetry in the distribution of attention, in which attention is preferentially directed towards the left side (Bowers and Heilman 1980;Jewell and McCourt 2000;Nicholls 2012;Thomas 2015). Pseudoneglect has been mainly reported in line bisection tasks and in visual exploration (Jewell and McCourt 2000;Foulsham et al 2013;Nuthmann and Matthias 2014).…”