Ignoring minority while generalizing about a group, any theoretical reference? In conversation, we might define a particular group by the characteristics that the majority of that group holds even if a minority in that group doesn’t possess those characteristics.  

Some possible examples:


Human being eats meats (even though ~3-5% of human are total vegetarians)
Russians like vodka (many don’t drink there)
Asians are brown (though there are many who are white)
(Ignore the figures or classification it’s just for explaining purpose)


The point is, why are we programmed to make generalizations this way, i.e., disregard the small or even significant but minority of a group while taking it as a whole, this is understood by common sense, but, I was wondering is there a scientific basis for this, perhaps some kind of theory presented by someone or a research that established this rule?
I think the exceptions are implied. If someone says, "All Russians like vodka" then we understand that there are no exceptions to the rule. People get frustrated when you're overly specific about the percent of Russians who like vodka. Instead it's safer to just say Russians like vodka. And bears.

Influence: The Psychology of Persuasion talks about why we operate based on generalizations. We would freeze if we analysed all the details of every situation before we act, so we make generalizations.

Thinking, Fast and Slow is an excellent book talking about the latest research in human biases from one of the foremost experts in the field.