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Hakwan Lau, Brian Maniscalco; Short-term fatigue of perceptual decision making and metacognition. Journal of Vision 2013;13(9):647. doi: 10.1167/13.9.647.
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© ARVO (1962-2015); The Authors (2016-present)
In psychophysics experiments we typically give subjects short breaks between blocks of trials, presumably because they get "tired". Whereas earlier studies suggest it is difficult to maintain attention and vigilance over long periods of time, it is unclear precisely what mechanisms can benefit from rests after a short block just a few minutes. Here we show that within short blocks of 100 trials (approximately 5 minutes), there were clear instances of drops of both basic perceptual decision performance, as well as sensory metacognition capacity (i.e. how well one can introspectively distinguish between correct and incorrect perceptual decisions, by placing appropriate confidence ratings). Importantly, these two forms of short term "fatigue" effects show a trade-off relationship. In subjects whose basic perceptual performance was well maintained over time, the metacognitive fatigue effect was stronger. This result violates the prediction of a single-process signal detection model in which the same mechanism gives rise to both perceptual decisions and confidence. However, despite the dissociation, the two mechansims likely depend on common resources, which explains the trade-off relationship between the two. Based on structural MRI brain images of individual subjects, we assessed the gray matter volume of their frontal polar area, a region that has been linked to visual metacognition. We found that this region may play a role in supplying the common resources that support both the maintenance of perceptual performance and metacognition, as variability of its volume accounts for individual differences in behavior. This model is further tested by two experiments in which reduced demand of metacognition led to better maintenance of perceptual performance over time. Overall, these results support the view that during breaks between short blocks, it is the higher-level perceptual decision mechanisms, rather than low level sensory machinery, that benefit most from rest.
Meeting abstract presented at VSS 2013
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