Effort tracks difficulty
Motivational intensity theory proposes that people spend only as much effort as a task seems to require. Effort rises with difficulty until the task looks impossible or no longer worth it, at which point it falls away sharply. The strength of a person's desire sets the upper limit, and does not fix the amount spent.
Effort as a cost
Newer accounts treat mental effort as something the brain prices. In the expected value of control view, people decide how much cognitive control to apply by comparing likely rewards with the cost of exerting it. Opportunity cost models add that effort feels unpleasant partly because it signals that attention could be used elsewhere.
Open questions
Researchers still disagree about why effort feels costly. Explanations include limited processing capacity, competition between tasks and learned expectations about reward. Measuring effort is also hard, since self-report, heart-based indices and task performance do not always agree.
Further reading
- Brehm, J. W., & Self, E. A. (1989). The intensity of motivation. Annual Review of Psychology, 40, 109-131.
- Shenhav, A., Botvinick, M. M., & Cohen, J. D. (2013). The expected value of control: An integrative theory of anterior cingulate cortex function. Neuron, 79, 217-240.
- Kurzban, R., Duckworth, A., Kable, J. W., & Myers, J. (2013). An opportunity cost model of subjective effort and task performance. Behavioral and Brain Sciences, 36, 661-679.