Reward evokes value-independent arousal and value-dependent reinforcement processing as dissociable physiological consequences

Abstract

Reward is traditionally thought to drive value-dependent reinforcement processing, whereas recent work suggests reward may instead raise arousal that mimics reinforcement. Because reinforcement and arousal depend on partly distinct neuromodulatory systems yet are co-triggered by reward, they have been widely treated as closely linked, though rarely tested directly, leaving reward's physiological consequences difficult to interpret. We manipulated the value of a primary reward by varying thirst while independently inducing arousal with sound, and measured pupil diameter and electroencephalographic activity. High- and low-value rewards produced comparable pupil dilation, indicating value-independent arousal. In contrast, only high-value reward increased alpha-band power, progressing from anterior to posterior regions, whereas low-value reward and sound produced similar alpha suppression without regional progression. Thus, reward evokes two dissociable consequences: value-independent arousal and value-dependent reinforcement. Rather than a single coupled process, these arise through separable mechanisms, providing a physiological framework for distinguishing each mechanism's contribution to reward processing.