Abstract
Humans are often tasked with making decisions about bundles of multiple items and very little is known about how the human brain aggregates, computes, and represents value in such cases. We investigated how the brain evaluates consumer items, both individually and in bundles, and how this activity relates to choice behavior. Human participants (N=14; 7 female, 7 male) completed a three-day deep-fMRI protocol while we elicited behavioral valuations for single and bundled items. Behaviorally, we find that bundle values are sub-additively discounted compared to the sum of individual item values. Neurally, we find that the same distributed network in pre-frontal cortex computes the value of a bundle and its constituent individual items, but the value representation undergoes a normalization that actively rescales across bundle and single item contexts. These findings suggest that generalized value regions contextually adapt within a valuation hierarchy, as opposed to utilizing an absolute value code.
Significance Statement Humans routinely choose among bundles—meals, device-plus-plan, vacation packages—yet how the brain evaluates multi-component options is unclear. Behaviorally, we show that bundle values are sub-additive relative to the sum of their parts. Using a three-day deep-fMRI protocol, we find that ventromedial prefrontal cortex and a distributed prefrontal network encode value for both single items and bundles, indicating a condition-independent, general value code. Critically, this code is scaled by context: activity is attenuated for bundles, and representational analyses favor models with relative, normalized value over absolute value. These findings reconcile a putative “common currency” with divisive normalization, demonstrating that value representations generalize across objects yet rescale to their distribution—an important principle for multi-component choice.
Footnotes
We would like to thank Whitney Griggs for assisting with data collection.
This work was supported by a National Institute of Mental Health Caltech Conte Center grant project on the neurobiology of social decision-making (P50MH094258) to JPOD, a National Institute on Drug Abuse (R01DA040011) grant to JPOD and LC, and a SSHRC Insight Development Grant (430-2019-00246) to RW.
