In another experiment, Dr. Bem had subjects choose which of two curtains on a computer screen hid a photograph; the other curtain hid nothing but a blank screen.

A software program randomly posted a picture behind one curtain or the other — but only after the participant made a choice. Still, the participants beat chance, by 53 percent to 50 percent, at least when the photos being posted were erotic ones. They did not do better than chance on negative or neutral photos.

“What I showed was that unselected subjects could sense the erotic photos,” Dr. Bem said, “but my guess is that if you use more talented people, who are better at this, they could find any of the photos.”

In recent weeks science bloggers, researchers and assorted skeptics have challenged Dr. Bem’s methods and his statistics, with many critiques digging deep into the arcane but important fine points of crunching numbers. (Others question his intentions. “He’s got a great sense of humor,” said Dr. Hyman, of Oregon. “I wouldn’t rule out that this is an elaborate joke.”)