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Measuring Delay Discounting in Humans Using an Adjusting Amount Task
Published on: January 9, 2016
Effort discounting in human nucleus accumbens.
Matthew M Botvinick1, Stacy Huffstetler, Joseph T McGuire
1Princeton University, Princeton, New Jersey, USA. matthewb@princeton.edu
Cognitive, Affective & Behavioral Neuroscience
|February 28, 2009
Summary
Effort discounting, where reward value decreases with effort, shows a neural basis in the brain's nucleus accumbens. Higher mental effort led to lower nucleus accumbens activation for the same reward.
Area of Science:
- Neuroscience
- Behavioral Economics
- Cognitive Science
Background:
- Behavioral and economic research indicates that the perceived value of a reward decreases as the effort required to obtain it increases (effort discounting).
- The nucleus accumbens (NAcc) is a key brain region involved in processing reward information and value.
- Previous studies suggest the NAcc encodes reference-dependent reward information, but its response to varying effort demands was not directly examined.
Purpose of the Study:
- To provide the first direct neural evidence for the principle of effort discounting.
- To investigate how neural responses in the human nucleus accumbens (NAcc) are modulated by both reward magnitude and the mental effort required for reward acquisition.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was employed to measure brain activity in human participants.
- Neural responses were recorded in the nucleus accumbens (NAcc) while participants undertook tasks involving monetary rewards with varying effort demands.
- Activation patterns in the NAcc and dorsal anterior cingulate cortex (dACC) were analyzed in relation to reward outcome and mental effort.
Main Results:
- Nucleus accumbens (NAcc) activation varied significantly with both the magnitude of the monetary reward and the level of mental effort required.
- For a constant reward amount, NAcc activation was significantly lower when the mental effort demand was high compared to when it was low.
- The magnitude of this effort-related modulation in the NAcc positively correlated with preceding activation in the dorsal anterior cingulate cortex (dACC).
Conclusions:
- The study presents the first direct neural evidence supporting the concept of effort discounting in the human brain.
- The nucleus accumbens (NAcc) exhibits a neural analogue of effort discounting, showing reduced activation with increased mental effort for equivalent rewards.
- The dorsal anterior cingulate cortex (dACC) may play a role in monitoring effort demands and mediating the subjective experience of effort, influencing NAcc responses.
