Show a man a picture of an attractive woman, and he might play riskier blackjack. With a real-life pretty woman watching, he might cross traffic against a red light. Such exhibitions of agility and bravado are the behavioral equivalent in humans of physical attributes such as antlers and horns in animals. “Mate with me,” they signal to women. “I can brave danger to defend you and the children.”

So says Lei Chang, a psychologist at the Chinese University of Hong Kong. With colleagues there and at China’s Hebei University, Chang wondered wheth­er military weaponry and parapherna­lia hold the same seductive value as antlers, horns and risky behavior, allowing warriors to best nonwarriors in the competition for mates. The researchers also speculated about war itself. When raping and pillaging, armies resemble chimps on intergroup sex raids. Might warfare actually be driven by the opportunity it offers males to impregnate females, willing and not willing?

To begin to address such questions, Chang showed men pictures of women and tested for statistically significant effects of those pictures on men’s attitudes about war and on their cognitive processes related to war. As he and his colleagues describe in the online March 23 Personality and Social Psychology Bulletin, they asked the men to rate their agreement with war-supporting statements. Men’s responses demonstrated a positive, significant statistical correlation between seeing photographs of attractive faces and endorsing war-supporting statements. This correlation was not demonstrated for photographs of unattractive women’s faces, and the researchers found no statistically significant effect on women of pictures of either attractive or unattractive men in any measure related to war.

Chang and his colleagues suggest that any warring-mating relation in men is probably an evolutionary holdover from pre–Homo sapiens days, which explains why raping and pillaging are, unfortunately, alive and well.