Abstract
Salient visual stimuli capture attention and trigger an eye-movement toward its location reflexively, regardless of an observer’s intentions. Here we aim to investigate the effect of aging (1) on the extent to which salient yet task-irrelevant stimuli capture saccades, and (2) on the ability to selectively suppress such oculomotor responses. Young and older adults were asked to direct their eyes to a target appearing in a stimulus array. Analysis of overall performance shows that saccades to the target object were disrupted by the appearance of a task-irrelevant abrupt-onset distractor when the location of this distractor did not coincide with that of the target object. Conditional capture function analyses revealed that, compared to young adults, older adults were more susceptible to oculomotor capture, and exhibited deficient selective suppression of the responses captured by task-irrelevant distractors. These effects were uncorrelated, suggesting two independent sources off age-related decline. Thus, with advancing age, salient visual distractors become more distracting; in part because they trigger reflexive eye-movements more potently; in part because of failing top-down control over such reflexes. The fact that these process-specific age effects remained concealed in overall oculomotor performance analyses emphasizes the utility of looking beyond the surface; indeed, there may be more than meets the eye.
Highlights
When our actions are determined by the environment rather than by a conscious plan to act, such actions are often called stimulusdriven or exogenous
For the conditional capture functions (CCF) this means a negative slope toward asymptote, that is, toward the minimum chance of moving to the distractor with increasing saccade RT (SRT)
Eye-movements to the distractor rapidly reach an asymptote in the CCF, after which little further performance benefits are gained by responding even slower
Summary
When our actions are determined by the environment rather than by a conscious plan to act, such actions are often called stimulusdriven or exogenous. Distributional analysis will be used to assess the build-up of top-down control of eye-movements in an oculomotor capture task. This task, originally devised by Theeuwes et al (1998), involves searching for a color singleton in a stimulus array that has six circles positioned on an imaginary circle around a central fixation point. The circle not changing color forms the target. With the color change an abrupt-onset distractor in the form of an extra circle is presented. Subjects are to react manually to the orientation of a line segment inside the target circle that is only recognizable when the eyes fixate on the correct circle directly. The automatic movement of the eyes toward an irrelevant onset distractor was termed oculomotor capture
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