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Christopher Benwell, Monika Harvey, Stephanie Gardner, Gregor Thut; Stimulus- and state-dependence of systematic bias in spatial attention: Additive effects of stimulus-size and time-on-task. Journal of Vision 2012;12(9):571. doi: 10.1167/12.9.571.
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Systematic biases in spatial attention are a common finding. In the general population, a systematic leftward bias is typically observed (pseudo-neglect), possibly as a consequence of right hemisphere dominance for visuospatial attention. However, this leftward bias can cross-over to a systematic rightward bias with changes in stimulus and state factors (such as line length and arousal). The processes governing these changes are still unknown. Here we tested models of spatial attention as to their ability to account for these effects. To this end, we experimentally manipulated both stimulus and state factors, while healthy participants performed a computerized version of a landmark task. State was manipulated by time-on-task (>1 hour) leading to increased fatigue and a reliable left- to rightward shift in spatial bias. Stimulus was manipulated by presenting long or short lines. An attenuation of the leftward bias was observed in short compared to long lines. Importantly, we found time-on-task and line length effects to be additive suggesting a common denominator for line bisection across all conditions, which is in disagreement with models that assume that bisection decisions in long and short lines are governed by distinct processes (Magnitude estimation vs. Global/local distinction). Our findings emphasize the dynamic rather than static nature of spatial biases in midline judgement. They are best captured by theories of spatial attention positing that spatial bias is flexibly modulated, and subject to interhemispheric balance which can change over time or conditions to accommodate task demands or reflect fatigue.
Meeting abstract presented at VSS 2012
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