From ancient mythology to modern advertising, the face of a beautiful woman has been regarded as a powerful motivator of men's behavior. Now a group of researchers based at Massachusetts General Hospital (MGH) has shown that, while heterosexual men recognize attractiveness in both female and male faces, they will expend effort to increase their viewing of attractive female faces only. The research also shows that areas of the brain previously identified as responding to such rewards as food, drugs and money also respond to facial beauty. The study appears in the November 8 issue of Neuron. "Our group has been studying the physiological mechanisms that underlie a variety of motivated behaviors," says Hans Breiter, MD, of the Motivation and Emotion Neuroscience Center in the MGH Department of Radiology, the paper's author and leader of the research team. "While many neuroscientists have been studying the visual processing of faces, we wanted to find out if watching beautiful faces can itself be rewarding and can activate the brain's motivation centers."
To answer these questions, the researchers conducted three experiments with groups of young, heterosexual men. (Men were chosen as study subjects because other recent research has shown that women's response to facial stimuli can change during their menstrual cycles.) Each experiment utilized a series of 80 photographs of faces that fell into four standard categories: beautiful females, average females, beautiful males, and average males.
One group of men was asked to evaluate the faces from 1 ("very unattractive") to 7 ("very attractive"). The participants were not told of the faces' standard categories. Another group was able to control how long they viewed each face by pressing certain keyboard keys - they could either decrease or increase the amount of time a face was displayed. And a third group had images taken of their brains as they viewed the faces; the functional MRI (fMRI) images focused on areas of the brain previously identified as being activated by such stimuli as food, money and drugs like cocaine.
Nancy Etcoff, PhD, an MGH psychologist and one of the study's lead authors, explains, "Earlier studies that I and others have conducted follow evidence that the perception of beauty is inborn, that similar features are regarded as beautiful universally. If beauty is indeed hard-wired into the brain by natural selection, we would expect to find circuits in the brain that respond to beauty." Etcoff is author of Survival of the Prettiest: The Science of Beauty, as well as a number of research studies in the area of facial recognition.
In the study's evaluation phase, participants' ratings of the faces they viewed corresponded to the faces' established ratings, and attractive males received ratings similar to those given attractive females. However, in the keypress task, the participants clearly worked to increase the time they viewed the attractive female faces and to decrease the time all other faces, including attractive males, were displayed.
The brain imaging study found that the same brain areas previously identified as part of a "reward circuitry," showed increased response to the viewing of attractive females only. In fact, the reward areas exhibited decreased activity when the young male participants viewed the attractive male faces.
"It looks like there can be a difference between what the brain 'likes,' an image that is judged to be attractive, and what the brain 'wants,' something that is regarded as a reward in and of itself," says Breiter, who is a psychiatrist. "It's particularly interesting that the attractive male faces actually produced what could be considered an aversion response, even though they had been recognized as attractive."
Etcoff adds, "This is the first time we've seen that what is often regarded as a social stimulus can activate these areas, which are in very old, prelanguage parts of the brain. While we know that experience, learning and personal idiosyncracies all have an impact on attraction between particular individuals, these results show that this basic reward response is deeply seated in human nature."
