Figure 1.
Schematic of the experimental stimuli. A, Participants were first shown a five-outcome mixed gamble, where each outcome was associated with a probability of occurrence. This base gamble was displayed for 4 or 6 s. B, They were then presented with two options for improving the gambles, and had 6 s to choose between these. In the gain-focus trials, they chose between adding money to the extreme gain (Gmax) or to the reference outcome, which changed the overall probability of winning (Pmax). In the loss-focus trials, they chose between adding money to the extreme loss (loss-minimizing, Lmin) outcome or to the Pmax outcome. After the 6 s decision phase, two arrows identified the buttons corresponding to each choice and participants indicated their preference by pressing the appropriate button as quickly as possible. A fresh trial appeared after a variable interval of 4, 6 or 8 s, with no feedback given after each trial. C, A subset of modified gambles was resolved at the end of the experiment. The five-outcome gamble was displayed with probabilities translated to numbers from 1 to 100. A random number identifying the winning outcome changed rapidly at the bottom of the screen. After a variable delay of 2–6 s, the number generated identified the winning outcome for that gamble. A message indicating the outcome was displayed for 2 s, followed by a variable interval of 2, 4 or 6 s before the next trial.