Fig. 1.

Experimental design. A: prestudy rating. One or two days before coming to the laboratory, participants rated the attractiveness of 1,000 everyday items on a scale of 1 (very unattractive) to 9 (very attractive). Based on the individual ratings, we selected 450 low-value and 450 high-value items for each participant, which were used in the low- and high-value conditions, respectively (see C). B: sample items, as classified for 1 of the participants. All of the items had the same objective market value (100 yen); in the actual experiment, the Japanese rather than English word for each item was displayed, and images were comparable to those shown here but obtained from the Internet. C: sequential choice task used during scanning. In each trial, for choice 1, 2 numbers were presented for up to 4 s on the left and right side of the monitor, and participants chose 1 of the 2 sides. One number corresponded to the number of choices, that is, the number of items (1, 2, 4, or 8) available from which they would be able to choose in choice 2 should they choose the choice option in choice 1. The color on which this number was displayed indicated whether the items were of low or high subjective value (here: green for high and orange for low value; color scheme holds for all figures). The other number corresponded to a monetary amount (10, 30, 50, 70, 90, or 110 yen) that participants would receive in choice 2 if they chose the monetary amount option instead of the choice option in choice 1. All brain activations reported (Figs. 3–6) are from choice 1. The option chosen in choice 1 was highlighted for 1 s, followed by a delay of 5–6 s. Choice 2 followed, for which 8 items were always displayed for 5 s, regardless of the option chosen in choice 1 and the number of choice alternatives. This allowed us to hold overall visual stimulation constant for all trial types. If participants had chosen the choice option in choice 1, they would now select either a low- or high-value item, depending on condition; otherwise, they would select a monetary item. The number of items available to choose from was equal to the number of items displayed in choice 1. To match difficulty of choosing the final outcome in the choice and the monetary amount options, we showed as many monetary amount duplicates as we would have shown in the corresponding choice option (illustrated is the case of 2 instances per outcome). Moreover, the proportion of duplicate monetary amounts shown in choice 2 was inversely related to the number of items offered in choice 1. After a delay of 2–3 s, the chosen item or monetary amount was displayed for 2 s. The participants then had 3 s to rate the attractiveness of the chosen item. After an intertrial interval of 2–3 s, the next trial started. ¥, yen.