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Jonathan Zadra, Simone Schnall, Arthur L. Weltman, Dennis Proffitt; Direct Physiological Evidence for an Economy of Action: Bioenergetics and the Perception of Spatial Layout. Journal of Vision 2010;10(7):54. doi: 10.1167/10.7.54.
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A good deal of evidence supports the notion that physiological state and the anticipated energetic demands of acting on the environment affect perception (e.g. Proffitt, 2006). Until recently, however, the role of such bioenergetic factors in the perception of spatial layout could only be inferred. Here, we directly assessed the role of bioenergetics by manipulating blood glucose (BG) levels (glucose is the primary source of energy for immediate muscular action). In each experiment, participants ingested either a glucose- or artificially-sweetened (placebo) drink, and multiple blood samples were obtained to assess changes in BG. Two experiments assessing perception of hill slant showed that people who ingested the glucose drink perceived hills to be less steep. An experiment in which participants gave distance estimates before and then again after ingesting a drink revealed that participants given glucose subsequently perceived distances to be shorter while those given the placebo did not. Furthermore, a battery of self-report measures assessed individual differences on a host of bioenergetically relevant properties. Regardless of the experimental manipulation, individuals with a reduced energy state perceived hills to be steeper and distances to be greater. A final study tested highly trained cyclists on two separate days before and after 45 minutes of intense pedaling on a stationary bike. They ingested glucose drinks at regular intervals on one day and placebo drinks on the other. After exercising, participants perceived distances to be shorter when given glucose and greater when given placebo drinks. Multiple direct physiological measures obtained during exercise indicated that across experimental conditions, greater energy expenditure and lower BG levels predicted greater distance estimates, and multiple indicators of physical fitness (heart rate, oxygen consumption, blood lactate) independently predicted shorter distance estimates for more fit individuals. These findings are consistent with the view that spatial perceptions are influenced by bioenergetic factors.
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