Some 80 women of various hair colors were tested on their mental capacity to work quickly and precisely in a series of psychometric tests. Before sitting the tests, half the participants had to read "dumb blonde" jokes, such as:

"Why do blondes open yogurt pots while still at the supermarket? -- Because it says 'Open Here' on the lid."

"No blonde woman believes she is stupid," said Jens Foerster a social psychologist from the International University Bremen in northern Germany on Wednesday.
"But after exposure to negative social-stereotypes about them, the fair-haired participants performed significantly more slowly in the tests."