What is mental effort: a clinical perspective

Abstract

Although mental effort is a frequently used term, it is poorly defined and understood. In neuroscience research, the term is used to mean both the cognitive ‘work’ that is done in meeting task demands, and the subjective experience of performing that work. We argue that this dual usage is problematic, as many neuropsychiatric conditions are characterised by specific changes either in the cognitive apparatus that carries out the work, or in the subjective experience that accompanies it. We suggest that the most coherent and clinically useful perspective on mental effort is that it is a subjective experience. This makes a clear distinction between cognitive impairments arising from changes in the cognitive apparatus, as in dementia and brain injury, and those arising from subjective difficulties in carrying out the cognitive work, as in attention deficit hyperactivity disorder, depression, and other motivational disorders. We review recent advances in neuroscience research, suggesting the experience of effort has emerged to control task switches so as to minimise ‘costs’ relative to ‘benefits.’ We consider how these advances can contribute to our understanding of the experience of increased effort perception in clinical populations. We suggest that this more specific framing of mental effort will offer a deeper understanding of the mechanisms of cognitive impairments in differing clinical groups, and will ultimately facilitate better therapeutic interventions.