Weizhen Xie (UC Riverside)
Effects of concurrent physical effort on working memory and cognitive control

Cognitive processing is often paired with physical effort in daily life, but is often separated in the lab setting. To counter this issue, we investigate the interaction between effortful physical action and visual working memory (VWM), a central cognitive process, to find any shared mechanisms between physical effort and cognitive effort. In Experiment 1, we investigated the tradeoff between physical effort and cognitive effort using a novel choice paradigm. In this task, participants repeatedly choose between a handgrip task and a VWM change detection task, with correct responses rewarded monetarily. For each task, both the effort level (handgrip strength to be retained over delay interval) and number of to-be-remembered items is parametrically manipulated. As expected, the probability of choosing each task decreased as its effort level increased. Choice performance is fit with a hierarchical Bayesian decision model allowing us to equate a physical load with a cognitive load. The resulting equivalent cognitive load (VWM set size) shows a linear relationship with physical load in log scale. To investigate this further, Experiment 2 investigated the effect of concurrent physical load on VWM capacity. Participants were instructed to hold the handgrip at either 20% (low load) or 40% (high load) of their maximum handgrip strength while performing a VWM change detection task. A difference in K estimates is found between high load and low load at set size 6. Interestingly, the shift in the subjective equivalent numbers of VSTM items from 20% to 45% maximum hand strength correlates with the reduction in the number of actually retained VSTM items due to the increase of physical load from 20% to 45% maximum hand strength. Additional behavioral and ERP findings on the detrimental effects of physical efforts on cognitive control will also be discussed. Together these Results suggest a shared mechanism between physical and VWM effort.