Monday, March 25, 2013

In Two Minds: Dual-Process Accounts of Reasoning

Evans, J.S. (2003). In two minds: dual-process accounts of reasoning. TRENDS in Cognitive Sciences, Volume 7 (10), 454-459.

Sometimes we take action before we’ve even realized we’re thinking about it. We hold our hand out to catch a ball; we produce a well-formed sentence. At other times, we use our brains to work out a problem like the answer to a difficult math equation, or to form an opinion on a particular issue. In this review paper, Evans (2003) describes these two distinct forms of reasoning, and argues that they are supported by separate cognitive systems in the brain.

System 1 is sometimes called our implicit reasoning, or unconscious system. It is thought to be the universal cognition that is shared between humans and other animals. Even though the brain goes through many steps using this type of reasoning, we’re usually only aware of the end product (in Evan’s terms, ‘only the final product is posted to consciousness’). System 1 processes are based on associative learning that activates specific neural networks. As a result, System 1 knowledge is based on prior experiences and beliefs. When we experience a flame and the sensation of heat together repeatedly, we begin to associate fire with heat and pull away from fire even without thinking about it. Evan’s argues that the learning mechanisms of this system are domain-general, but that the function is domain-specific.

System 2 is thought to have evolved more recently and to be unique to humans. Its processes are slower, operate in sequence, and are under voluntary control. This system requires the use of working memory (WM) and is therefore restricted to the limitations of WM (e.g., how much you can hold in mind at one time). The purpose of System 2 is for abstract, hypothetical thinking. Consider the example of how I decided to get to campus today: System 1 instinctively reaches for the car keys as this is how I have travelled to campus all winter long; however, System 2 constructs a mental model of possibilities, such as taking into account it is now Spring, the temperature is warmer, and the roads are clear, therefore I could dust of my bicycle and get some exercise while I travel to school, which has health benefits compared to sitting in a car driving. System 2 would also take into consideration the fact that my bicycle will require a tune up in order to use it and I unfortunately do not have enough time to do the work if I am to arrive on time, therefore I should drive to campus today in my car and make some time on the weekend to get my bicycle ready. It is clear from this example that the two processes interact with one another depending on what is being reasoned.

One technique used to investigate these two systems is a deductive reasoning paradigm. The participant judges whether an argument is true or false requiring reasoning using System 2. Sometimes the argument uses familiar information in a believable or unbelievable way. Judgments influenced by this prior knowledge reflect the influence of System 1.  Neuropsychological studies employing functional magnetic resonance imaging (fMRI) provides additional evidence for the distinction between System 1 and 2 processes because separate brain areas are activated on tasks tapping System 1 and/or 2.

Of interest to our lab is how these systems might influence language learning.

Blogger: Ian Gallant is about to graduate from the Masters of Clinical Science degree in Speech Language Pathology. He hangs out in the LWM lab on a regular basis.