The original Iowa Gambling Task studies decision making using a cards. The participant needs to choose one out of four card decks (named A,B,C, and D). The participant can win or loose money with each card.

The task was designed by Bechera and colleagues, 1994. Note that author Antonio Damasio is one of the most famous cognitive neuroscientists and that this specific paper is very highly cited.

The original paper used real cards, whereas nowadays, the Iowa Gambling Task is often computer based. The task was originally developed to detect problems patients with damage to the ventromedial prefrontal cortex. This part of the brain is, among other things, involved in processing risk, fear, emotion, and decision making:

Following damage to the ventromedial prefrontal cortex, humans develop a defect in real-life decision-making, which contrasts with otherwise normal intellectual functions. Currently, there is no neuropsychological probe to detect in the laboratory, and the cognitive and neural mechanisms responsible for this defect have resisted explanation. Here, using a novel task which simulates real-life decision-making in the way it factors uncertainty of premises and outcomes, as well as reward and punishment, we find that prefrontal patients, unlike controls, are oblivious to the future consequences of their actions, and seem to be guided by immediate prospects only. This finding offers, for the first time, the possibility of detecting these patients' elusive impairment in the laboratory, measuring it, and investigating its possible causes.

— Bechara et al.

The original scheme

In the original paper (Bechera and colleagues, 1994), the following procedure was followed:

  • There were 4 decks of cards (A, B, C, and D)

  • Participants had to choose in total 100 cards, one at the time

  • Each time they choose a card, they get feedback about winning and/or loosing some money

  • Participants did not know what each card would yield in advance (i.e., like a lottery)

  • Participants started with a "loan" of of $2000 and were told to make a profit

  • Decks A and B always yielded $100

  • Decks C and D always yielded $50

  • For each card chosen, there is a 50% chance of having to pay a penalty as well. For decks A and B, the penalty is $250, whereas for decks C and D it is $50.

"Decks A and B are disadvantageous in the long run because they cost the most in the long run, while decks C and D are advantageous because they result in an overall gain int he long run." (Bechara et al., 1994, p.10).

About this implementation

The basics are the same except that this is an online experiment. Instead of four decks of cards, you now see four "buttons" like on a slot machine labeled A, B, C, or D.

The rewards are the same as in the original study. As you will note, it is pretty easy to figure out. Of course, you can make the rules more complicated by changing the code a bit.


When you are analyzing the data, you need to think carefully about what exactly you want to find out.

  • One interesting outcome is how often people decided for the "high risk" decks (A/B) or the "low risk" decks (C/D).

  • Another interesting question is how long it took people to decide before they made a low or high risk decision.

Currently, there are no "direct" easy ways to analyze this within the PsyToolkit website. Instead you are recommended to look at the "raw" files and read them in yourself (e.g., with R) and look for the outcomes you are interested in.

Run the demo

In this experiment, you will see a basic instruction followed by 100 trials of the Iowa Gambling Task. Each time, you need to select A,B,C, or D and you can win/loose some money. At the top of the screen you see how much money you have. You start with 2000 dollars.

Data output file

In PsyToolkit, the data output file is simply a textfile. The save line of the PsyToolkit experiment script determines what is being saved in the data output file. Typically, for each experimental trial, you would have exactly one line in your text file, and each number/word on that line gives you the information you need for your data analysis, such as the condition, response speed, and whether an error was made.

Meaning of the columns in the output datafile. You need this information for your data analysis.

Colum Meaning


reaction time (mouse click)


which button click (A=1,B=2,C=3,D=4)


whether there was a fee to pay (1) or not (0)


the amount in bank before participant clicked


the amount in bank after participant clicked


the amount won ($50 or $100)


the fee to pay ($0, $50, or $250)


If you have a PsyToolkit account, you can upload the zipfile directly to your PsyToolkit account. Watch a video on how to do that. If you want to upload the zipfile into your PsyToolkit account, make sure the file is not automatically uncompressed (some browsers, especially Mac Safari, by default uncompress zip files). Read here how to easily deal with this.

Further reading

  • Bechara, A., Damasio A.R., Damasio H., Anderson S.W. (1994). Insensitivity to future consequences following damage to human prefrontal cortex. Cognition, 50, 7-15.