Pupil-linked arousal counteracts the positive effects of reward anticipation on incidental memory encoding

The anticipation of a potential reward has been shown to enhance episodic memory, but the underlying mechanisms remain unclear. While previous research has highlighted the role of attention in improving memory for reward-associated stimuli, the impact of arousal during encoding has been less explored. In this study, we used a monetary incentive delay task followed by a surprise memory test 24 h later to examine whether pupil-linked arousal mediates the beneficial effect of reward anticipation on memory. Contrary to our expectations, we found that higher arousal during encoding impaired subsequent memory performance, counteracting the dominant positive direct effect of reward anticipation on memory. This result suggests that, rather than facilitating memory, increased arousal during reward anticipation may disrupt encoding, possibly by heightening decision urgency. Our findings offer new insights into the complex interplay between reward anticipation, arousal, and memory encoding, highlighting the importance of considering time pressure as a potential influencing factor when studying the central arousal system.