No single feature is necessary. People are influenced by context.
People know information about variability, as well as central tendency.
4-door Sedan Greyhound Bus, Cambus Siamese Cat, Tabby Cat Irish Wolfhound, Samoyed Basic level has largest increase in similarity among members. But, while basic for humans, not for animals. Color categories are perceptually based, not linguistically based. Told some way in which the flamingo and the bat differed. If not, they go by appearances.