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Dynamic Perception of Well-Learned Perceptual Objects

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Abstract

Eight initially novel objects with four features were learned by three participants over about 70 sessions in a variety of present-absent search tasks. This article analyzes and models trials with a single object presented for test. The features of the object were presented simultaneously, or successively at rates fast enough that the objects appeared to be simultaneous (inter-stimulus intervals were 16, 33, or 50 ms). Classification of a test object as target or foil required a conjunction of two features. When successively presented, features diagnostic for target presence could arrive first or last, and vice versa for features diagnostic for foil presence. Two results were particularly important: (1) the order in which target-diagnostic or foil-diagnostic features appeared produced large changes in accuracy and response times; (2) simultaneous feature presentation produced lower accuracy than sequential presentation with target-diagnostic features arriving first, despite the delay in such features arriving. The results required a dynamic model for perception and decision. The model has features perceived at independent times. It accumulates evidence at each moment based on the features perceived up to that time, and the diagnosticity of those features for classifying the test object as target or foil. The model also assumes that configurations of features provide evidence as processing continues: when all four features of an object are perceived the evidence points without error to the correct response. The results and modeling support the view that perceptual and decision processes operate concurrently and interactively during identification, recognition, and classification of well-learned objects, rather than in successive stages.

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Notes

  1. Standard evidence accumulation processes are both time- and state-homogeneous. A number of newer approaches we discuss are time-inhomogeneous: the rate of progression through the states changes over time. We present a model best described as both time and state inhomogeneous, because the states include the features that have been perceived and these change as evidence is accumulated.

  2. Due to discretization of time, and the use of integral response boundaries and steps, there are undesirable cases that arise. For example, when the response boundaries are equally spaced from the starting position, e.g., at A = +2 and B = −2, the process will always finish after an even number of steps. In order to smooth the process, we allow the walk at each epoch to stay with some probability in the same position, rather than take a step.

  3. Parameters 2–5 must have integer values, so their posterior distributions are not normally distributed.

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Correspondence to Samuel M. Harding.

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Harding, S.M., Cousineau, D. & Shiffrin, R.M. Dynamic Perception of Well-Learned Perceptual Objects. Comput Brain Behav 4, 497–518 (2021). https://doi.org/10.1007/s42113-021-00107-0

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  • DOI: https://doi.org/10.1007/s42113-021-00107-0

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