Dissociating self-generated volition from externally-generated motivation

Insight into motivational processes may be gained by examining measures of willingness to exert effort for rewards, which have been linked to neuropsychiatric symptoms of anhedonia and apathy. However, while much work has focused on the development of models of motivation based on classic tasks of e...

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Bibliographic Details
Published in:	PloS one 2020-05, Vol.15 (5), p.e0232949-e0232949
Main Authors:	Morris, Laurel S, Norbury, Agnes, Smith, Derek A, Harrison, Neil A, Voon, Valerie, Murrough, James W
Format:	Article
Language:	eng
Subjects:	Adult Analysis Anhedonia Anxiety Apathy Bias Biology and Life Sciences Cognition Cognitive ability Decision making Decision Making - physiology Development and progression Emotional behavior Female Healthy Volunteers Hedonic response Humans Intrinsic motivation Keyboards Male Medical schools Medicine Medicine and Health Sciences Mental depression Mental disorders Middle Aged Motivation Motivation - physiology Neurosciences Novels Physical Sciences Prejudice Psychiatry Psychological aspects Reinforcement Research and Analysis Methods Reward Social Sciences Volition - physiology Will Will (Philosophy)
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Summary:	Insight into motivational processes may be gained by examining measures of willingness to exert effort for rewards, which have been linked to neuropsychiatric symptoms of anhedonia and apathy. However, while much work has focused on the development of models of motivation based on classic tasks of externally-generated levels of effort for reward, there has been less focus on the question of self-generated motivation or volition. We developed a task that aims to capture separate measures of self-generated and externally-generated motivation, with two task variants for physical and cognitive effort, and sought to test and validate this measure in two populations of healthy volunteers (N = 27 and N = 28). Similar to previous reports, a sigmoid function represented a better overall fit to the effort-reward data than a linear or Weibull model. Individual sigmoid function shapes were governed by two free parameters: bias (the amount of reward needed for effort initiation) and reward insensitivity (the amount of increase in reward needed to accelerate effort expenditure). For both physical and cognitive effort, bias was higher in the self-generated condition, indicating reduced self-generated volitional effort initiation, compared to externally-generated effort initiation, across effort domains. Bias against initial effort initiation in the self-generated condition was related to a specific dimensional measure of anticipatory anhedonia. For physical effort only, reward insensitivity was also higher in the self-generated condition compared to the externally-generated motivation condition, indicating lower self-generated effort acceleration. This work provides a novel objective measure of self-generated motivation that may provide insights into mechanisms of anhedonia and related symptoms.
ISSN:	1932-6203 1932-6203