Overgeneralization is an error that involves coming to a conclusion based on information that is too general and/or not specific enough. This is like looking at a whale and concluding that "since it lives in water and has fins it must be a fish." This conclusion doesn't take into consideration all the facts, such as whales breathe air and nurse their young, which makes it a mammal. In science, as well as other areas of study, overgeneralization can lead to significant mistakes.
Another example is when a man would think that all women are bad drivers just because of a lady acquaintance who happened to be not so good at driving. Overgeneralization is one of the most common types of cognitive distortions based on Aaron Beck’s cognitive theory. These different types were developed by David Burns, a student of Beck.