Before reading about this study it’s important to recap the dual processing model of judgement and decision making. According to Kahneman (and others) we have two systems of processing information. System one is fast and unconscious, while system two is slower and considers more factors. The system of processing we use will affect our judgement, which in turn will influence the decisions we make.
In this experiment, Bechara et al. (2000) compared the decision making of participants with damage to their ventromedial prefrontal cortices (vmPFC) with healthy controls. The vmPFC has been shown in other research to play a role in regulating impulsive behaviour. From this study, it’s possible to deduce that perhaps the vmPFC regulates behaviour through its ability to enable us to use system two processing. That is to say, if we can take our time to make a decision and resist impulsive instincts, we might be able to think through our decision making and make a better choice. This study has multiple possible applications, especially in the field of criminology, which will explored later in this post.
The researchers compared the decisions made by 17 healthy controls and 8 patients with lesions in their vmPFCs during the Iowa Gambling Task. This commonly used experimental procedure (which you can watch a video of below and even try for yourself) involves participants choosing from four decks of cards. It’s a bit tricky to explain, so it really is best to watch a demonstration or even give it a go yourself.
To summarize the paradigm, there are four decks and participants select a card from one of the four decks. They do this for 100 trials. They win or lose money based on their decisions. What they don’t know from the start is that two of the decks have a high initial reward but high long-term risk factor (Decks B and D in the diagram below), whereas two decks have low initial risk and low reward. But actually, in the long run, the low risk and low reward decks are more advantageous because they will result in winning more money because they will lose less in the long-run.
It usually takes participants about 20 or 30 trials before they can realize the pattern and healthy controls typically opt for the “safe” desks, using Deck A and C. In other words, they are able to resist the initial temptation of going for the high reward decks, because they can see that in the long-term this is a bad choice; they are using system two processing of the information to make this decision because they can think through the consequences of that decision.
The results of this study showed the same trend: healthy participants were able to slowly move away from the disadvantageous decks (B and D) and chose more from the advantageous decks that had low initial reward but higher long-term gains (A and C).
The vmPFC lesion participants, however, did not demonstrate this same shift in behaviour. They continued to choose from the disadvantageous decks, regardless of the negative consequences.
In their discussion, the researchers note that “…the results reinforce the notion that VM lesion patients are oblivious to the future and are guided predominantly by immediate prospects. This `myopia for the future’ persists in the face of increasing adverse consequences” (Bechara et al., 2000).
This study suggests that the vmPFC plays a role in our ability to use system two processing. If this part of our brain is damaged, we may not be able to think past initial impulses, way up more factors, and base our decisions on consequences, which are all fundamental characteristics of system two processing. This might lead to decisions being made based on system one, which is impulsive and automatic.
- Thinking and Decision Making: This study provides evidence that system two processing might have a biological base in the vmPFC. Damage to this part of the brain, therefore, could affect our thinking and decision making.
- Localization of Brain Function: Similar to the point above, this study can be used to demonstrate the role of the vmPFC in system two processing and decision making.
- Techniques to Study the Brain and Behaviour: This study highlights the value of being able to use MRI to identify patients with damage to a particular part of the brain to study. This enables the functions of specific parts of the brain to be explored.
- Research Methods Brain and Behaviour: Sometimes a variable that is hypothesized to have an effect is desired to be studied, but researchers can’t manipulate this variable – the vmPFC lesions in this case. This is where the quasi experimental method is valuable.
- Ethics in the Brain and Behaviour: In this particular case, one example of an ethical consideration based on the results of the study could be anonymity. The results reveal interesting and unique features about participants’ decision making based on the damage to the brain. This is sensitive information and so participant details should be anonymous and confident. If this were publicized, in extreme cases this could even lead to manipulation of vmPFC lesion patients.
- Criminology: This study is a core component of our study of criminology in IB Psychology because it shows how damage to the PFC may affect behaviour. Low function and volume in the PFC has been correlated with violent crime and antisocial adults. This could be because this abnormality in brain function reduces the ability to think through one’s actions and consider long-term consequences. Without this ability to make good decisions, people may act on impulse. This is important to comprehend because in this unit we explore the role of serotonin and testosterone on the PFC.
Critical Thinking Questions
- Ethics: What other ethical considerations do you think are relevant to this study?
- Generalizability: Is it really possible for behavior observed in the Iowa Gambling Task to be applied to explain violent behaviour?
- Internal Validity: Is this study really measuring system one and two processing? It is plausible to apply these results to this concept, but this was not the researchers’ initial intention. Are there any reasons why the methodology might influence the applicability to the dual processing model of judgement and decision making?
You can play the Iowa gambling task here.
Disclaimer: This link goes to an external site that requires downloading software, and while we have had no issues with this software or the site ourselves, we take no responsibility for the results of downloading software from external sites. This must be done at the users own discretion.
You can see a short video by PBS that outlines the Iowa Gambling Task here. David Eagleman is a leading neuroscientist and his article in the Atlantic “The Brain on Trial” is a fascinating read. He hosts a documentary series called “The Brain with David Eagleman.”
Here is another short video from academicmediaservices that outlines the procedures of the Iowa Gambling Task, although it doesn’t explain what’s behind the four decks.
Bechara, Antoine, Daniel Tranel, and Hanna Damasio. “Characterization
of the Decision-making Deficit of Patients with Ventromedial Prefrontal
Cortex Lesions.” Brain. Oxford University Press, 01 Nov. 2000.
Dixon, Travis. IB Psychology: A Student’s Guide. Themantic Education, Yokohama Japan. 2017 (Purchase).
You can read the full original article here.