This is a classic n-armed bandit task. Participants choose between two slot machines (or bandits) with the aim of winning as many points as possible over the task. Each bandit has a different probability of paying out and different number of points on offer. Participants will learn by trial-and-error whether a bandit is:
For half of the experiment the environment is stable (i.e. 60 trials with a fixed 75:25 reinforcement schedule), in the other half the environment is volatile (i.e. a 80:20 reinforcement schedule that switches every 20 trials).
This task uses spreadsheets to assign magnitude and probability values on each trial. Different spreadsheets decide which version the participant does, i.e:
A simple bit of scripting is used to decide if participants win or lose on a specific trial, and to add winning points to the total score.
If you want to see how I created this experiment, organised and analysed the data, you can watch my video tutorials on Gorilla Academy in the Learning section.
This study is a replication of Behrens et al (2007)
Grös et al (2007)