Belief bias

Belief bias is the tendency to judge the strength of arguments based on the plausibility of their conclusion rather than how strongly they support that conclusion. A person is more likely to accept arguments that supports a conclusion that aligns with our values, believes and prior knowledge, while rejecting counter arguments to the conclusion.   Belief bias is an extremely common and therefore significant form of error; we can easily be blinded by our beliefs and reach the wrong conclusion. Belief bias has been found to influence various reasoning tasks, including conditional reasoning, relation reasoning and transitive reasoning.

A syllogism is a kind of logical argument in which one proposition (the conclusion) is inferred from two or more others (the premises) of a specific form. The classical example of a valid syllogism is:

An example of an invalid syllogism is:

Typically, a majority of test subjects in studies incorrectly identify this syllogism as one in which the conclusion follows from the premises. It might be true in the real world that a) girls study and b) this is because they are ambitious. However, this argument is a fallacy, because the conclusion is not supported by its premises. The validity of an argument is different from the truth of its conclusion: there are valid arguments for false conclusions and invalid arguments for true conclusions. Hence, it is an error to judge the validity of an argument from the plausibility of its conclusion. This is the reasoning error known as belief bias.

When a person gives a response that is determined by the believability of the conclusion rather than logical validity, this is referred to as belief bias only when syllogism are used. This phenomenon is so closely related to syllogistic reasoning that when it does occur, in areas such as Wason's selection task or the THOG problem, it is called "memory cueing" or the "effects of content".

Many researchers in thinking and reasoning have provided evidence for a dual-process cognitive approach to reasoning, judgement and decision making. They argue that these two systems (system 1 and system 2) engage in a constant battle for control over our brain to reason and make decisions. System 1 can be described as an automated system characterised by “unconscious” , "intuitive" and "rapid"”; whereas system 2 is said to be a controlled system, characterised by “conscious”, “Analytic” and “Slow”; some researchers (Reber 1993, Stanovich 1999) even claimed to have found a link between general intelligence and the effectiveness of decision making. It is important that note that the dual-process cognitive theory is different from the two minds hypothesis. A research done by Johnathan Evans in 2007 provided evidence for the view that System 1 which serves as a quick heuristic processor fights for control over System 2’s slower analytical approach. In the experiment, participants were asked to evaluate syllogisms that have valid arguments with unconvincing conclusions; valid arguments with convincing conclusions; invalid arguments with unconvincing conclusions; invalid arguments with convincing conclusions. The results show that when the conclusion is believable, people blindly accept invalid conclusions more so than invalid arguments are accepted.

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