Fig. 1.

Value adaptation task. (A) Bid trial and rating trial designs. In bid trials, subjects reported their willingness to pay for a snack food item using a slider bar. In rating trials, subjects reported the pleasantness of a presented item on a visual analog scale. (B) Experimental session block design. Blocks of bid trials (Test block) and rating trials (Adapt block) alternated across a session. Test blocks presented all 30 items, and Adapt blocks presented a subset of 10 low (Lo) or 10 high (Hi) value items, enabling a quantification of how valuation behavior changed following adaptation to either low- or high-value exposure. The sequence of Adapt block conditions (Lo-Hi or Hi-Lo) was randomized across subjects. (C) Repeat bid stability. First versus third bids for individual items are plotted for all subjects. Consistent with items having intrinsic subjective valuations, repeat bids were significantly correlated across the population (r = 0.89, P = 5.40 × 10⁻⁴⁶) as well as in each individual subject (P < 0.05). (D) Example bid distribution and item classification. Data show sorted mean bids for all 30 items (error bars, SEM). The 10 lowest- and 10 highest-value items were designated Lo-value (blue) and Hi-value (red) items, respectively. (E) Example item rank structure. Crosses show the value rank of items presented in Test blocks (black), Hi-value Adapt blocks (red), and Lo-value Adapt blocks (blue).