While jogging around the neighborhood, you are more likely to get bitten by someone’s pet dog than by any member of the canine species.
If the foregoing statement sounds about right, consider that a pet dog is a canine.
Related to representativeness is the conjunction fallacy, which is the logically inconsistent assumption that a more specific condition is more probable than a general one. Another example:
Linda is 31 years old, single, outspoken, and quite bright. She majored in philosophy. As a student, she was deeply concerned with social justice and discrimination, and participated in civil-rights demonstrations.
Which is more probable?
Linda is a librarian.
Linda is a librarian and active in the feminist movement.
85% of those asked thought option 2 was more likely, even as it is a more specific observation than option 1.
The representativeness heuristic makes option 2 seem more like the personality profile of Linda than the vaguer option 1, even as 2 is statistically less probable. The mind is more satisfied with an easy fullness than a sheer statistic.