Oh Oh, Visual Capabilities Seriously Limited

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“Despite the brain’s immense processing power, it has finite resources…visual imagery is severely limited by the perceptual and phenomenal bottleneck of visual representation. These capacity limits appear to be independent of generation time, depend on visual feature heterogeneity, are attenuated by concurrent retinal stimulation and are endowed with good metacognition. Additionally, the precision of visual representation declines rapidly with the number of stimuli, which is governed by a simple power law. We anticipate that this assay will be important for mapping the limits of human information processing.

Despite the great processing power of the human brain, when we are asked to remember or process multiple things at once our performance tends to decline with more items. These capacity limits are found across most cognitive domains, such as general intelligence, multi-tasking, auditory and visual short-term memory and visual attention. Much of the research into human cognitive capacity limits to date has focused on high-level working memory and attentional capacity limits, however exactly where these capacity limits originate is still an open question. Surprisingly, relatively little research has examined any low-level sensory contributions to these limitations, such as the inherent two-dimensional map-like representation of the visual cortex, which likely intrinsically limits the amount of visual information that can be concurrently held.

Mental imagery research suggests that both the vividness and sensory strength of mental imagery plays an important role in almost any cognitive function that involves some form of sensory simulation…

Together our data suggests that visual imagery has severe capacity limits to the amount of content that can be simultaneously generated. It is unlikely that a strict rigid ‘slot’-like model drives these limits, with decreases in both strength and precision emerging with increases in total content. Further, the heterogeneity of the content places further limitations on representational sensory strength suggesting that the type of information being imagined, and not just the number of items, influences capacity limits. It is unlikely that such capacity limitations are driven by limits to attentional resources for two reasons. First, the perceptual capacity limits were accompanied by phenomenal limits, with participants reporting lower levels of imagery vividness with larger…

visual imagery appears to have its own capacity limits with decreases in strength, vividness and precision with increases in set size. We propose that these capacity limits are due, in part, to an individual’s ability, or lack there of, to create precise ‘maps’ of the mental representations in the early visual cortex. Competition between generated content imposed by the inherent anatomical limitations of the two dimensional representational architecture of V1, likely results in the observed limitations to visual representations in thought.”

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