Most people, if asked to judge which family is more likely--family A with three children consisting of an firstborn daughter, a son in the middle and a lastborn daughter or family B with three daughters--most people will judge that family A is more likely to occur. However, the odds for either family A or B is the exactly same, 12.5%. However, the prototype of "family with three children" held by most people consists a family with both sons and daughters in any order (which make up 75% of families with three children). Thus the unconscious prototype that people have of a family of three children leads them to overestimate the probability that a family will have exactly a daughter, son, and daughter. This reasoning error illustrates:

a. the gambler's fallacy.
b. the availability heuristic.
c. the representativeness heuristic.
d. confirmation bias.

Answer: c. the representativeness heuristic.