Control costs

Matthew Botvinick
Princeton University

The Law of Less Work states that when two courses of behavior lead to the same terminal 
reward, there will be a preference for the less effortful course of behavior.  This principle has 
been overwhelmingly validated in the case of physical effort.  However, it has been also 
been widely assumed to hold for mental or cognitive effort.  Although this idea has been 
used to explain a wide range of phenomena, there has been surprisingly little attempt to test 
it.  Over the past several years, we've developed behavioral methods for studying the role of 
cognitive effort demands in decision making.  The results collected so far provide clear 
validation for the notion that cognitive effort is subjectively costly.  People will, in fact, 
forego monetary reward in order to avoid demands for mental effort, an effect that cannot 
be explained in terms of error avoidance or minimization of time on task. The form of effort 
involved appears to be linked specifically to the mobilization of executive functions or 
cognitive control.  Through a series of fMRI studies, we have tied control costs to activation 
of regions within medial and lateral prefrontal cortex, and demonstrated an effect of control 
costs on subcortical reward processing.  In the most recent phase of research, we have 
studied effort-based decision making through the lens of economic labor supply theory, and 
also investigated potential links between cognitive demand avoidance and individual 
differences in self-control.  I will provide an overview of established findings, and also 
discuss some brand new results that we are seeking to better understand.