Abstract
Cognitive effort is typically aversive, evident in people's tendency to avoid cognitively demanding tasks. The ‘cost of control’ hypothesis suggests that engagement of cognitive control systems of the brain makes a task costly and the currency of that cost is a reduction in anticipated rewards. However, prior studies have relied on binary hard versus easy task subtractions to manipulate cognitive effort and so have not tested this hypothesis in “dose-response” fashion. In a sample of 50 participants, we parametrically manipulated the level of effort during fMRI scanning by systematically increasing cognitive control demands during a demand-selection paradigm over six levels. As expected, frontoparietal control network (FPN) activity increased, and reward network activity decreased, as control demands increased across tasks. However, avoidance behavior was not attributable to the change in FPN activity, lending only partial support to the cost of control hypothesis. By contrast, we unexpectedly observed that the de-activation of a task-negative brain network corresponding to the Default Mode Network (DMN) across levels of the cognitive control manipulation predicted the change in avoidance. In summary, we find partial support for the cost of control hypothesis, while highlighting the role of task-negative brain networks in modulating effort avoidance behavior.
Highlights
Cognitive effort influences our everyday decisions about whether to perform challenging mental tasks
Participants were highly accurate on the categorization task across both phases, and participants missed the deadline on few trials (2.3% of Learning phase trials, SE=0.003, 1.4% of Test phase trials, SE=0.01)
The ‘Cost of control’ hypothesis makes two core proposals: 1) effort registers as disutility by the brain, 2) the cost derives from cognitive control demands
Summary
Cognitive effort influences our everyday decisions about whether to perform challenging mental tasks. One account of demand avoidance behavior is the ‘cost of effort' hypothesis, according to which the brain codes cognitive effort as disutility (Botvinick, 2007) Consistent with this hypothesis, the value of reward is discounted as a function of effort requirements (Westbrook et al, 2013). This hypothesis predicts that this cost should be computed by the same networks that typically process reward, such as the mesolimbic dopaminergic system, including the medial prefrontal cortex and the ventral striatum (VS) This prediction is supported by at least one fMRI study which observed reduced activation in VS following effortful task performance (Botvinick et al, 2009). Evidence that the brain registers effort as disutility has received limited, albeit conflicting, support
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