Hidden in every attempt at gaining knowledge is an array of old beliefs ensconced at the corner of your mind, ready to ambush your reasoning at any moment and jump to a conclusion when you least expect it. Belief bias refers to these moments when the old haunts the new, molding the latter to its form and mitigating any chance for progress. By understanding how our old beliefs interfere with our cognition, we can learn why, more often than we like to admit, we tend to only believe what we want to believe.
What Is Belief Bias?
Belief bias is a cognitive bias where we evaluate the validity of an argument based on how believable its conclusion sounds to us. Our old beliefs determine how believable a knowledge claim appears, regardless of whether it is logically valid or invalid. Belief bias is considered an error of reasoning where our existing beliefs interfere with our evaluation of knowledge and is one of the earliest cognitive biases to be discovered in the field of cognitive psychology. This error of reasoning particularly disrupts our capacity for syllogistic reasoning – to draw a logical conclusion from a set of two or more premises.
Consider the following example. From the premises (1) “All healthy people exercise” and (2) “John exercises”, we can conclude that “John is a healthy person”. Although the conclusion may seem believable because we associate physical exercise with health, the argument is logically invalid. John is not necessarily healthy because he exercises, and may very well be extremely unhealthy. Nothing in the argument validates the conclusion, yet because it sounds believable, we accept it as truthful. Premise (1) states that exercise is a condition for being healthy, not that being healthy is a condition for exercise.
The argument is an example of a logical fallacy known as affirming the consequent. Just as in the case of our assessment of John’s health, belief bias may distort our assessment of knowledge about ourselves, the world, and even the things that matter to us the most. We will believe what is believable to us regardless of whether it is supported by sufficient evidence or not. Effectively, our old beliefs limit our acceptance of knowledge to the borders of what we already know and believe.
What Is the Significance of Belief Bias?
The significance of belief bias lies in how it determines our knowledge and decisions. Belief bias leads us to accept believable, yet invalid, knowledge, and reject unbelievable, yet valid, knowledge. In so doing, it distorts our cognition to a great extent, which could, in extreme cases, result in a false worldview and self-image. By rushing to a conclusion based on what we already believe, we risk being led to unwanted decisions.
This is particularly evident in political discourse where an argument for extreme and unjust measures is justified by a claim that appeals to common values and beliefs. Here, belief bias may lead people to accept the argument regardless of its logical validity and immorality. On a personal level, belief bias may influence very important decisions in your life, because what you believe to be true informs all your decisions. When that knowledge is distorted, you may make wrong decisions about matters you care about.
What Causes Belief Bias?
A prominent explanation of belief bias is the dual-process theory. According to this theory, we have two distinct types of mental processes – implicit and explicit, also known as System 1 and System 2. The System 1 implicit process is considered automatic. According to psychologist John Bargh, it is automatic in so far as it is non-intentional, unconscious, uncontrollable, and efficient (i.e. requiring the least cognitive resources to operate). System 1 contains our implicit body of knowledge, including our old beliefs.
The System 2 explicit process refers to our conscious and deliberate capacity for sequential rational thinking. It is a rule-based analytic system, the source of our recent evolutionary ability of logical thinking. Unlike System 1, System 2 requires more cognitive resources and is therefore slower.
According to cognitive psychologist Jonathan Evans, dual-process theories “essentially posit two minds in one brain with a range of experimental psychological evidence showing that the two systems compete for control of our inferences and actions” (Evans, 2003). Belief bias is generally explained as a moment when System 1 cognitively overpowers System 2 in this cognitive competition, resulting in an error of reasoning. This is more likely to happen when one must arrive at a conclusion or decision under time pressure, because our implicit reasoning process is more efficient and faster than our conscious and deliberate rational process.
So, the next time you need to make an important judgment or decision, take your time.
