Imagine a scenario where you're in a queue and patiently waiting to pay for your groceries. As you move forward you suddenly become aware of the face of the checkout operator. The face of the twenty-five-year-old male is contorted into a face that can only be described as miserable. Even as people cheerfully say hi and move off, the face of the checkout operator doesn't change.
You feel yourself getting heckled and conclude that he must be a laugh a minute at home - a real life and soul of the party. Other similar irritated thoughts go through your mind...congratulations you have just committed the fundamental attribution error.
The fundamental attribution error is the tendency for an individual to ascribe personality traits without considering alternative explanations such as environmental causes. Another example would be to see someone slip and conclude that they are clumsy by nature, and not posit that the ground might be slippery or that there is an issue with the footwear.
The fundamental attribution appeals to our tendency to seek quick explanations rather than see alternate explanations. In this way, it also appeals to our habit of judging quickly.
Next time you're at the checkout, and someone is apparently miserable, try and think of possible reasons for this such as having to work on a weekend or the death of a friend. In this way, you train yourself to work beyond the error and mental heuristic as well as develop a spirit of non-judgment.
Have you ever attributed someone with a negative personality trait...only to discover there was another reason for the way they acted at the time?