Fig. 4. Comparisons for cognitive tests in humans and rodents.

Humans and rodents can both perform cognitive tasks that feature actions to obtain rewards (a) The primary differences in testing are that humans can receive monetary rewards whereas rodents tend to be given food rewards. Furthermore, rodents require more initial training to learn the action (i.e., lever pressing or nose poking). To test for goal-directed action (b) both humans and rodents are trained to associate two actions (left and right button/lever presses) with two separate food rewards. One of these rewards is then devalued through an aversive video (cockroaches on the food item) for humans or feeding to satiety in rodents. Healthy controls will demonstrate outcome-specific devaluation by biasing their response towards the food reward that was not devalued. Serial reversal learning (c) requires the subject to learn a simple discrimination between two choices of which one is associated with a reward. Once certain criteria are met, the contingencies are reversed so that the non-rewarded stimulus is now rewarded and the previously rewarded stimulus does not attain a reward. This is classified as the first reversal. Once the criteria are met for the new contingencies, the rewarding stimulus is switched again (back to the original pairings) for the second reversal. This switching back and forth continues until completion of the test