Short-term memory capacity and chronic stress levels predict cognitive effort choice as a function of reward level and effort demand

Every day, we make choices about how much effort we are willing and able to use to achieve the outcomes we desire against the backdrop of constantly shifting effort demands and available rewards. While factors like visual short-term memory and chronic stress levels can predict responses to stable cognitive effort demands, we do not yet know whether they constrain ones choices of higher effort trials for larger rewards when task demands and potential outcomes shift over time. Here, we examined whether these factors predicted the choice to deploy cognitive effort given increasing effort demands and the tendency to deploy effort given shifting reward availability. Undergraduate participants first performed an online visual short-term memory task to assess capacity for visuospatial short-term memory. They then completed a series of choice trials where they could choose between high-effort, high-reward or low-effort, low-reward trials. In two blocks, we varied either the effort required on high-effort trials or the reward offered on both trial types. We found that visual short-term memory predicted the likelihood of choosing high-effort trials given shifting rewards, while chronic stress and everyday preferences for cognitively effortful strategies predicted the tendency to deploy increasing amounts of effort for a stable reward. Furthermore, participants subjective reports show a strong focus on attentional processes, and balancing rewards and losses, when making decisions about how much effort to deploy. These findings shed light on distinct trait-level factors associated with cognitive effort choices given shifting demands and outcomes. Significance statementWe must often choose how much work to put in to complete everyday tasks. However, we do not know what behavioural factors drive these choices in humans when the effort required to complete a task - or potential rewards - shifts over time. In a visual short-term memory task adapted from rodent work, we found that those with higher visual short-term memory ability chose more high effort trials as effort demands increased, while chronic stress and everyday preferences for effortful strategies predicted more effort for a reward. Furthermore, participants described prioritizing sustaining attention in order to successfully complete the task. These findings shed light on distinct trait-level factors associated with cognitive effort choices given shifting demands and outcomes.