Thirteen patients aged 17 to 39 were tested for cooperative behaviors in a computer-simulated ball-tossing game with three fictitious players. The three simulated players were programmed to each send 70 percent, 30 percent, and 10 percent of its tosses to the subject. The subject was told that each participant, including himself or herself, would receive 2 euros for each ball received. A group of 13 healthy control subjects, while playing the computer game, soon recognized the player most likely to reciprocate and preferentially sent balls to that player. After they received a dose of placebo, the autistic subjects tossed their balls with even frequencies to all three virtual players, which differed significantly from healthy controls, who were tested once without either placebo or oxytocin.