On this site you find the experimental materials (including an online demo of the study), data, and the analysis script.

1 Demo Version of Experiment

To run an online demo version click here.

You can also run an offline version. To download the program files (.zip) of the experiment, click here. Once downloaded, the experiment can be run offline in a web browser. To do so, open the “index.html” file that is included in the files.

Note: When running the demo, you will see three buttons displayed on the screen (that need to be operated by the experimenter), “I” (for “impulse”), “D” (for “draw”), and “N” (for “next” trial). The buttons can either be operated by the computer mouse or by the corresponding keys on your keyboard.

This is how a regular trials works:

  1. You first have to give an impulse (“I”) to shuffle the balls in the urns.
  2. You then have to select an urn by clicking on it, whereupon a green frame will occur around the selected urn.
  3. You then have to draw a ball from that urn (“D”).
  4. You then can proceed to the next trials (“N”).

At the end of the experiment, an explorer window will open so you can save the data file to your hard drive.

2 Data

2.1 Data set information

The data set contains the following columns:

  • subjID: a random subject ID (anonymous)
  • age: subjects’ age in year
  • sex: subjects’ gender
  • trialNr: an identifier for the different trials in the experiment
  • n1Urn1: number of balls of Color 1 in Urn 1 (the left urn)
  • n2Urn1: number of balls of Color 2 in Urn 1
  • n1Urn2: number of balls of Color 1 in Urn 2
  • n2Urn2: number of balls of Color 2 in Urn 2
  • col1: the color that is Color 1 (yellow vs. blue)
  • col2: the color that is Color 2 (yellow vs. blue)
  • selectedUrn: the urn selected by a participant in that trial
  • correctUrn: the (correct) urn that has the higher proportion of winning balls in that trial
  • correctAns: coding of whether the participant selected the correct urn (1) or not (0)
  • drawnCol: the color of the ball that was (actually) drawn in that trial
  • winCol: the winning color
  • feedBack: the feedback that the participant saw in that trial
  • fbCongr: coding of whether the feedback the participant received matched the choice quality (bad feedback if bad urn was chosen; positive feedback if the good urn was chosen, etc.)
  • sID_new: a re-coded subject ID

2025 Sarah Placì.