Behavioral economics

In his just-published book, How Pleasure Works, Yale psychology professor Paul Bloom, described by Harvard psychologist Steven Pinker, as “among the deepest thinkers and clearest writers on the science of mind today,” writes:

Freud claimed "when you meet a human being, the first distinction you make is 'male or female' and you are accustomed to making the distinction with unhesitating certainty." This is true for me at least; I get e-mails from strangers with foreign names and when I can't tell whether the sender is a man or a woman, it is oddly unsettling. It shouldn’t matter — I have no intention of mating with them — but it does. When we see a baby in a diaper, the first question that many of us ask is: Is this a boy or it is a girl?

source: Dennis Prager