Behavioral Diagnostics Toolkit

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Faulty Reasoning

Quasi-Magical Thinking

Post hoc ergo propter hoc – Quasi-magical thinking describes our tendency to sometimes irrationally act as if we believe that our actions influence an outcome, even when we do not really hold that belief (e.g., blowing on dice before rolling them).
This is like Schrodinger’s Cat for psychologists. The belief that all conditional probabilities have a causal basis, even though we sometimes know that none exists. i.e., Our active participation is what causes any given outcome.

Peak-End Rule

Contrary to the idea that we take an average of how pleasant or unpleasant an experience was overall, this memory bias suggests that we are more likely to remember the most intense parts (positive or negative), as well as the manner in which the experience ended.

Outcome Bias

All's well that ends well…not! Occurs when the quality of a decision and/or the competence of the decision maker is judged solely on that decision’s outcome, rather than on the quality of the initial decision process given what was known at the time.

Illusory Correlation

The scientific oasis in the desert. We should always be extremely careful about the process through which we determine that two variables are related. We sometimes perceive that two variables are related when they are, in fact, not at all related.


The idea that any entity can be reduced to a number of core attributes that form its unique identity. Attributes are often considered permanent, unalterable, and eternal.

End of History Illusion

You can’t teach an old dog new tricks. The idea that a person has reached their capacity to absorb new information, tastes, and perspectives, and will simply not evolve or significantly any further.

Confirmation Bias

I reject your reality, and substitute my own! We seek evidence that confirms beliefs that we already hold, and become likely to ignore contrary positions.

Belief Bias

The end justifies the means. The strength of an argument can sometimes be assessed by the plausibility of of its conclusion, and its congruence with our prior beliefs, rather than the merits of the argument itself.