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Measuring the psychophysical effects of clutter on competitive visual selection in older and young adults

posted on 21.10.2021, 07:01 by Jason McCarley
The dataset attached are the mean data for each experimental participant.These are not the raw data. Each subject did multiple trials in each experimental condition, what is shown here are the mean response time and the accuracy rate for each condition.

This dataset contains data from an experiment that assessed the ability of young (Young adults: M = 21.26 years, SD = 2.62) and older adult subjects (Older audlts: M = 72.2 years, SD = 3.49) to divide attention between pairs of visual target objects that appeared either in the presence or absence of clutter.

The experimental task asked participants to render a same-different shape judgment of two target items each trial. Experiment 1 ran the experimental task using two sets of stimuli differing in their discriminability. The stimuli in one set were letters X and O, items that are distinguished by rudimentary visual features and were therefore highly discriminable. The stimuli in the second set were letters T and L randomly rotated in steps of 45°, items that are distinguished only by the spatial arrangement of their features and are therefore relatively difficult to discriminate.

Experiment 2 employed the same procedure but using triangles and arrows as high discriminability stimuli and using rotated letters T and F as low discriminability stimuli.

In both experiments, target items were drawn in colour and clutter, when it was present, was drawn in grey. The spatial separation between target items varied across trials.

An experimental session comprised 2 blocks of 32 practice trials each, followed by 15 blocks of 32 experimental trials each. A trial began with a 500 ms blank screen, followed by a 400 ms fixation interval then the imperative display.

During the first block of practice trials, the imperative display remained visible until a response was detected or the timeout limit was reached. For all of the following blocks, exposure duration for imperative display was limited to 200 ms in order to discourage eye movements. The trial then ended when a response was detected, or when a 2500 ms timeout limit was reached. A failure to respond before the timeout limit was classified an error.

Date coverage: 2010


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Prof Jason McCarley

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