Two experiments examined the effect of Object Substitution Masking (OSM) on the
perceptual errors in reporting the orientation of a target. In Experiment 1 a four-dot trailing mask
was compared with a simultaneous-noise mask. In Experiment 2, the four-dot and noise masks were
factorially-varied. Responses were modelled using a mixture regression-model and Bayesian-inference to deduce whether the relative impacts of OSM on guessing and precision were the same
as those of a noise mask, and thus whether the mechanism underpinning OSM is based on
increasing noise rather than a substitution process. Across both experiments, OSM was associated
with an increased guessing-rate when the mask trailed target offset, and a reduction in the precision
of the target representation (although the latter was less reliable across the two experiments).
Importantly, the noise mask also influenced both guessing and precision, but in a different manner,
suggesting that OSM is not simply caused by increasing noise. In Experiment 2 the effects of OSM
and simultaneous-noise interacted, suggesting the two manipulations involve common mechanisms.
Overall results suggest that OSM is often a consequence of a substitution process, but there is
evidence that the mask increases noise levels on trials where substitution doesn’t occur.
Pilling, MichaelGuest, DuncanAndrews, Mark
Faculty of Health and Life Sciences\Department of Psychology, Health and Professional Development
Year of publication: 2019Date of RADAR deposit: 2019-01-17
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