In a highly unusual critique published yesterday, the Stanford University biologist -- who used to be Barbara -- said his experience as both a man and a woman had given him an intensely personal insight into the biases that make it harder for women to succeed in science.

After he underwent a sex change nine years ago at the age of 42, Barres recalled, another scientist who was unaware of it was heard to say, "Ben Barres gave a great seminar today, but then his work is much better than his sister's."

And as a female undergraduate at MIT, Barres once solved a difficult math problem that stumped many male classmates, only to be told by a professor: "Your boyfriend must have solved it for you."

"By far," Barres wrote, "the main difference I have noticed is that people who don't know I am transgendered treat me with much more respect" than when he was a woman. "I can even complete a whole sentence without being interrupted by a man."