Fig. 1: Experimental study design.
A An example of a sequence of trials and (B) the overall structure of the reward learning task in the main study. Participants learned through trial and error which of two categories was more rewarding in each of 4 blocks (outcomes were $10 or $0); reward contingencies were probabilistic (0.75/0.25 reward probability); half the blocks included food stimuli (‘food task’, categories: ‘raw’ and ‘cooked/baked’ food, which served as a cover for low- and high-calorie food, respectively) or scene stimuli (‘control task’, categories: indoor and outdoor scenes). After completing one block of each task, participants experienced an emotional arousal manipulation in which they ‘spun’ a computerized wheel of fortune (0.50 probability of winning or losing $8). They next completed two more learning blocks of each task (order of blocks counterbalanced across participants). Participants completed self-ratings throughout the reward learning task (indicating level of ‘alertness’ (arousal), as well as hunger, thirst, and happiness) to check for changes induced by the emotional arousal manipulation. Food images (catalog numbers 280 and 143; Blechert J, Lender A, Polk S, Busch NA and Ohla K (2019). Food-Pics_Extended—An Image Database for Experimental Research on Eating and Appetite: Additional Images, Normative Ratings and an Updated Review. Front. Psychol. 10:307. https://doi.org/10.3389/fpsyg.2019.0030764) are released under a Creative Commons-Attribution-NonCommercial-Sharealike 3.0 license (https://creativecommons.org/licenses/by-nc-sa/3.0/).
