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Marcus Cappiello, Weizhen Xie, Weiwei Zhang; The Mental Muscle: Effects of Concurrent Effortful Physical Action on Visual Working Memory. Journal of Vision 2018;18(10):705. doi: 10.1167/18.10.705.
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Action and cognition are closely intertwined in everyday life. For example, human observers frequently incorporate eye movements in mental representations and processes. However, how concurrent physical activity influences cognition beyond the oculomotor system remains unclear. Here, we ask how exerting an effortful physical action, such as hand gripping, impacts visual working memory (VWM), a core cognitive process. Using a novel choice paradigm (Experiment 1), we first evaluated how holding a handgrip to different levels (20%, 30%, 45%, 65%, and 90%) of the maximal voluntary isometric contraction (MVC) equated in perceived effortfulness to holding different number of items (1, 2, 3, 4, and 6) in VWM. This iso-effort pattern (i.e., working memory load equivalent in effort to a given physical load) can be captured by a logarithmic function, suggesting a systematic tradeoff between these two types of effort, potentially due to some shared mechanisms for physical and cognitive efforts. Experiment 2 replicated these findings from Experiment 1 and further examined how exerting different levels of handgrip force (20% vs. 45% MVC) directly affected performance in a change detection task performed concurrently. We found that the physical load of 45% MVC (vs. 20% MVC) reduced the number of items retained in VWM at a memory set size of 6, but not at smaller memory set sizes. Critically, across participants this reduction significantly correlated with the decrease in the iso-effort working memory load from 45% to 20% MVC estimated from the choice paradigm, ruling out an alternative account based on general dual-task cost. Together, these findings provide preliminary support for the direct competition between physical and cognitive efforts. Given the ubiquitous involvement of effortful physical activities in everyday life, the current study sheds light on the extent to which some core cognitive processes may be affected by physical strain.
Meeting abstract presented at VSS 2018
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