Fiona Macpherson (2012) argues that various experimental results provide strong evidence in favor of the cognitive penetration of perceptual color experience. Moreover, she proposes a mechanism for how such cognitive penetration occurs. We argue, first, that the results on which Macpherson relies do not provide strong grounds for her claim of cognitive penetrability; and, second, that, if the results do reflect cognitive penetrability, then time-course considerations raise worries for her proposed mechanism. We base our arguments in part on several of our own experiments, reported herein.
A central goal in research on visual perception is to understand how the visual system represents the shapes of objects. According to many theorists, axes defined on the basis of object geometry provide a coordinate system for representing the locations and orientations of object parts. An important question that has received little attention concerns how object axes are defined—that is, what aspects of object geometry determine how axes are assigned to shapes? We evaluated 2 hypotheses. According to the elongated-part hypothesis, axes are defined on the basis an object’s most elongated part, such that, for example, the principal axis for a hatchet would coincide with the long axis of the hatchet’s handle. In contrast, the global-shape hypothesis holds that axes are defined on the basis of an object’s overall shape (e.g., for the hatchet, as the longest axis that spans the entire hatchet). Using a novel paradigm involving analysis of mirror-image confusions, we obtained evidence strongly supporting the elongated-part hypothesis. Our results also point to a role for secondary as well as principal axes in object shape representation.
Cognitive neuropsychological evidence is widely viewed as inherently flawed or weak, despite well-reasoned arguments to the contrary by many theorists. Rather than attempting yet another defence of cognitive neuropsychology on logical grounds, we point out through examples that in practice, cognitive neuropsychological evidence is widely accepted as valid and important, and has had a major impact on cognitive theory and research. Objections offered in the abstract rarely arise in the context of actual studies. We develop these points through examples from the domain of vision, discussing cerebral achromatopsia and akinetopsia, selective impairment and sparing of face recognition, perception-action dissociations, and blindsight.
Introduction
The Psychomotor Vigilance Test (PVT), the Multiple Sleep Latency Test (MSLT), and the Maintenance of Wakefulness Test (MWT) are widely used in both sleep research and clinical settings. The PVT measures reaction time to a visual stimulus, whereas time to sleep onset is measured in both the MSLT and MWT, which differ primarily with respect to the instructions (i.e., whether to try to fall asleep vs. stay awake). Compared to sleep latency tests, the PVT is relatively inexpensive and easy to administer, so it is advisable to delimit the conditions under which its administration is most appropriate.
Methods
A comprehensive search of sleep studies on healthy adults revealed 30 studies in which both PVTs and sleep latency tests were administered – usually to assess the effects of various interventions on sleepiness and vigilance. Two reviewers compiled findings from each study and graded the levels of outcome agreement based on whether a test intervention produced similar effects on vigilance across tests.
Results
Of the 13 studies that included both PVT and MWT of studies, a high level of agreement (based on the presence and direction significant effect on vigilance) between test outcomes was evident in 8 (61.5%) of the studies. In contrast, a considerably lower percentage of studies in which both the PVT and MSLT were performed (6 of 17 studies; 35.3%) had high agreement between test outcomes. It was also found that the MSLT was more sensitive to interventions (e.g., caffeine, sleep loss, and cognitive workload) than the PVT in the majority of studies in which there was low agreement (5 of 6 studies; 83.3%).
Conclusion
There is generally more agreement between PVT and MWT measures than between PVT and MSLT measures in studies involving sleep loss. This is most likely because the PVT and MWT both require application of effort to resist sleepiness, whereas the MSLT involves the withdrawal of resistance to sleepiness. This suggests that the PVT is potentially more useful in operational environments (where ability to sustain performance is the primary concern) than in clinical settings (where the focus is on determining the severity of sleepiness).
Support (If Any)
Department of Defense Military Operational Medicine Research Program (MOMRP)
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