Imaging Reveals what the Brain Values May Not be what it Buys

When humans see attractive faces, their brains are continually computing how much the experience is worth to them. New brain-imaging research shows it is even possible to predict how much people might be willing to pay for a particular face.

Researchers from Duke University Medical Center (Durham, NC, USA) discovered that as participants were watching a sequence of faces, their brains were simultaneously assessing those faces in two distinct ways: for the quality of the viewing experience and for what they would trade to see the face again. The research's findings were published in the Journal of Neuroscience online on February 16, 2010.

The investigators showed college-aged men a parade of female faces, intermixed with images of money, while measuring brain activation using functional magnetic resonance imaging (fMRI) scanning. In a later experiment, the same participants could pay more or less money to view more or less attractive faces.

"One part of the frontal cortex of our participants' brains increased in activation to more attractive faces, as if it computed those faces' hedonic [quality of the experience] value,” said senior author Scott Huettel, Ph.D., an associate professor of psychology & neuroscience who directs the Center for Neuroeconomic Studies at Duke. "A nearby brain region's activation also predicted those faces' economic value--specifically, how much money that person would be willing to trade to see another face of similar attractiveness.”

During the fMRI experiment, heterosexual men viewed a set of female faces that had earlier been rated for attractiveness by peers. Interspersed with the face pictures were pictures of money, shown in several denominations, which indicated real monetary gains or losses that the participant could later spend during the next phase of the experiment. The participants made a series of economic decisions: Should they spend more of their money to see a more attractive face, or spend less money but see a less attractive face? Each participant made about one hundred of these decisions, spending from 1 to 12 [U.S.] cents each time.

The researchers measured fMRI activation while the participants viewed the faces and money. In a region near the front of the brain, the anterior ventromedial prefrontal cortex (VMPFC), there was increased activation when participants saw a more attractive face or saw an image of a larger amount of money. That pattern of brain activation was comparatively stable across participants in the study. However, a little farther back in the brain, within the posterior VMPFC, the researchers also could see the relative activation to the faces compared to money, which strongly predicted how each person would later spend to see a more attractive face.

Dr. Huettel noted that findings from neuroscience might lead to new directions in marketing. "People often respond to images in a very idiosyncratic fashion,” he said. "While we can't use neuroscience to identify the best images for every person's brain, we could identify types of images that tend to modulate the right sorts of value signals--those that predict future purchases for a market segment.”

Lead author David V. Smith, a Duke graduate student in psychology & neuroscience, explained further, "Previous studies have shown that active decisions about the value of real goods, such as candy or consumer products, evoke activation in the VMPFC. Our study demonstrates that the VMPFC actually contains two signals for value: one that indicates how much value we are currently experiencing, and another that indicates how much we'd be willing to pay to have that experience again later.”

Why were all subjects male? "For this new study, we built on prior work from colleagues who showed that young adult males not only value the experience of seeing a female face, but will treat that experience like an economic good--they will trade experience for money in a predictable manner,” Dr. Huettel said. "We expect that the functioning of the brain's reward system is essentially similar between males and females. However, what sorts of stimuli seem attractive--whether an image of a face or some other social cue--may differ between the genders.”

Dr. Smith added that they plan to continue the research with other kinds of rewards, including different types of pictures. "A key issue in future research will be examining how different value signals are communicated between different parts of the brain to produce our decisions,” he concluded.

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Duke University Medical Center