The dual process theory of reasoning

Evans, J. S. B. (2003). In two minds: dual-process accounts of reasoning.Trends in cognitive sciences, 7(10), 454-459.‏http://faculty.weber.edu/eamsel/Classes/Methods%20(3610)/Old%20Sections/Fall%202010/Fall%202010%20Project/Evans%20(2003).pdf

This theory argues that reasoning is supported by two cognitive systems:

System A is evolutionarily old, and exists in animals too.  This is a set of autonomic subsystems that includes innate modules of input, and knowledge that is domain specific.  This system includes instinctive, born behaviors.    The system's processes are fast and automatic, and only their end result is accessible to consciousness.  An example of system A reasoning would be making a decision on the basis of past experience.

System B is evolutionarily new and exists only in humans.  This system allows for abstract and hypothetical thinking.  System B thinking is slow, and is limited by the capacity of working memory.  It is highly correlated with measures of general intelligence.  An example of system B reasoning would be making a decision about situations that have never happened before, by creating mental models or mental simulations of future possibilities. 

System B has an inhibitory function – it inhibits reactions that are based on beliefs and on prior knowledge, default reactions.  This inhibition requires a lot of effort and a large investment of attentional resources.

The two systems are competing for the control of our deduction processes and of our actions.  The systems are sometimes described as implicit (system A) and explicit (system B). 

This resembles, up to a certain point, fluid ability and executive functions (like system B) and crystallized knowledge (like system A), and also Cattell's investment theory.

This field is researched by paradigms that create a conflict between reactions based on logical thought processes and reactions  based on prior belief.  For example, people are given a logical syllogism  and have to judge which conclusions are necessarily drawn from the premises.

Intelligent adults are affected by the syllogism's content and not only by the extent to which the syllogism is logically valid.  According to the dual process theory, despite   trying to think logically as they were instructed to do, people find it hard to suppress the influence of prior beliefs which are competing efficiently for control of their reactions. 

Neuropsychological studies found that when people choose a right logical result which is contrary to their belief, a different area of the brain is activated than when they choose a result that fits with their belief but is logically wrong.

In this paper, the following example demonstrates the influence of content on logical reasoning (Wason's choice task):

In problem A, every card has a letter side and a number side.  One has to choose the cards that confirm or deny the statement: "if there is an A on one side of the card, then there is a 3 on the other side of the card".

In problem B, every card has a beverage side and an age side.  One has to choose the cards that confirm or deny the statement: "if a person is drinking beer, then that person must be over 18 years of age". 

The answer to problem A is A and 7.  The answer to problem B is "drinking beer" and "16 years of age".  Despite being similar problems, the abstract version, A, is much harder than the concrete version, B.  The content in version B makes it easier.  Many researchers think that problem A requires system B and problem B is solvable with the use of system A.