Satiety does not abolish Pavlovian-to-instrumental transfer but accelerates devaluation in humans
Environmental cues that predict palatable food can robustly drive behavior, override satiety signals and promote maladaptive eating habits. However, conventional human paradigms often fail to capture the dynamic interplay between hunger, satiety, and cue-induced behavioral actions. To address this, we built a novel automated dispenser synchronized with task events and integrated into an adapted human Pavlovian-to-instrumental transfer (PIT) paradigm to deliver real, consumable food rewards in real time--allowing participants to eat online and thereby induce satiation or sustain hunger. In one experiment, we manipulated food rewards by varying portion size and consumption timing. Large portions consumed immediately induced rapid satiation, whereas small, trial-by-trial portions kept participants non-satiated; correspondingly, large portions accelerated devaluation of the food reward--evidenced by a pronounced decline in instrumental responding--while small portions sustained cue-driven behavior over time. In a subsequent experiment, small, immediately consumed food rewards (which kept participants non-satiated) were directly compared with real-time monetary rewards. Although both reward types initially invigorated behavior, the motivational impact of monetary rewards declined quicker, suggesting that the absence of physiological feedback renders secondary reinforcers more vulnerable to rapid devaluation. These findings suggest that satiety accelerates, rather than abolishes, the influence of food-associated cues. The distinct temporal dynamics observed for food and monetary outcomes underscore the importance of real-time ingestion in human PIT paradigms, offering new insights into the mechanisms by which physiological states modulate cue-driven devaluation.