PubMed · 6665526
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W C Gogel, P McNulty. 1983. Perceived velocity as a function of reference mark density.. https://doi.org/10.1111/j.1467-9450.1983.tb00499.x
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We previously demonstrated that changing the apparent extent of a target's apparent motion-in-depth, by manipulating pictorial depth cues in the surrounding, affected perceptual judgements and manual pursuit to the same extent. Here, we investigated whether a different manipulation of the extent of motion (expanding and contracting the object itself) also has the same effect on both tasks. Objects were presented that changed in size as they moved on an elliptical path. The size was related to the object's position in the sagittal plane, suggesting additional motion in depth; therefore the illusion was expected to affect sagittal measures for both perception and action. We measured manual tracking and perceptual judgements of the lateral and sagittal extents of the object's elliptical trajectories. A significant correlation was found across subjects between the effect of the illusion on the perceptual and the motor task. As expected, the illusion only had a significant influence on the sagittal dimension. The size of this illusory effect was equal for perception and action.
Perspective change within a single environment is a slow and effortful process. However, little research has addressed perspective change across multiple environments. Using a task-set switching paradigm, subjects judged spatial relationships between target locations from differing perspectives. Response times were longer when successive trials probed different perspectives. However, this cost was greater when perspective was changed within a single environment compared to when it was changed across two environments. This result indicates that the processing of perspective change, and perhaps general spatial reasoning, differs in these two cases. Implications for theories of perspective change and environmental knowledge are discussed.
A model of cue-based probability judgment is developed within the framework of support theory. Cue diagnosticity is evaluated from experience as represented by error-free frequency counts. When presented with a pattern of cues, the diagnostic implications of each cue are assessed independently and then summed to arrive at an assessment of the support for a hypothesis, with greater weight placed on present than on absent cues. The model can also accommodate adjustment of support in light of the baserate or prior probability of a hypothesis. Support for alternatives packed together in a "residual" hypothesis is discounted; fewer cues are consulted in assessing support for alternatives as support for the focal hypothesis increases. Results of fitting this and several alternative models to data from four new multiple-cue probability learning experiments are reported.