Figure 3.

(A) Schematic of the risky decision-making task. Food-restricted rats are trained in operant chambers to make discrete-trial choices between two response levers. A press on one of the levers (“Lever one”) delivers a small, “safe” food reward (a single food pellet) and a press on the other (“Lever two”) delivers a large food reward (several food pellets) that is accompanied by a variable probability of footshock. Test sessions are organized into five blocks of trials, in which the probabilities of shock delivery are 0, 25, 50, 75, and 100% (usually in ascending order). Each block consists of 8–10 free-choice trials, which are preceded by 8 forced-choice trials used to familiarize rats with the probability of shock delivery for that block. The large reward is delivered after each choice of the large reward lever, irrespective of shock delivery [see Simon and Setlow (2012) for further details of task design]. (B) Mean (+/− SEM) performance of 42 male Long-Evans rats tested in the risky decision-making task. After 20–25 training sessions, rats on average prefer the large reward when the risk of accompanying shock is low, but shift their choices to the small, safe reward as the risk of shock increases.