German researchers asked 28 men — all heterosexual, and averaging 26 years of age — to look at a number of computer images. Some images were pornographic and some were nonsexual. The nonsexual images included pictures of people doing a number of activities, such as laughing, playing sports or carrying a weapon.

As the volunteers viewed the pictures, they touched a “yes” or “no” key to indicate whether or not the picture they were seeing was the same as one they had seen four slides previously.

The men logged a significantly greater number of incorrect answers when they viewed the porn than when they saw the nonsexual images. On average, they answered correctly 67 percent of the time when they viewed pornographic pictures but 80 percent of the time when they saw the nonsexual pictures.