Poor Bridget Jones. At the beginning of the first film about her diary and life, the character, played by actress Renée Zellweger, is fat and alone in her apartment where she mimes one of the great self-pitying song hits of all time: "All by Myself." But Bridget's problem may be more than skin deep.

In new research, reported in the current online issue of the journal Social Neuroscience, researchers from the University of Georgia and San Diego State University report for the first time that social exclusion actually causes changes in a person's brain function and can lead to poor decision-making and a diminished learning ability.

"Our findings indicate that social rejection can be a powerful influence on how people act," said W. Keith Campbell, a psychologist who led the research. The new research is the first to examine subjects' brain patterns following social exclusion using the magnetoencephalography (MEG) technique.

Other authors of the paper include Jean Twenge of San Diego State University; Brett Clementz and Jennifer McDowell, also psychology faculty members at UGA; and UGA graduate students Elizabeth Krusemark, Kara Dyckman and Amy Brunnell.

Researchers have known for a long time that there is a link between social exclusion and the failure of self-control. For instance, people who are rejected in social situations often respond by abusing alcohol, expressing aggression or performing poorly at school or work. (Bridget Jones chooses "vodka and Chaka Khan.")

The new study, however, is the first to use MEG to show that there are actual changes inside the brain when test subjects are manipulated to feel socially excluded. MEG is an imaging technique that measures the magnetic fields produced by electrical activity in the brain. It is most often used by physicians to localize brain tumors prior to surgery or to study the brain function of patients with epilepsy.

The subjects in the current study were 30 women undergraduates in a psychology course at UGA. Each one was asked to complete a written personality questionnaire. The team leading the experiment then said they would "feed the answers into a computer," which was, in fact, untrue. Instead, half of the sample, selected randomly, was told their answers showed they would "end up alone" later in life. The others were given a more neutral assessment of their social interactions.

"At this point, we gave each of the subjects a series of simple mathematical problems, taking 25 minutes, to solve on a computer screen in front of them while they were in the MEG machine," said Campbell. "We presented participants with 180 problems, and what we found was surprising."

The MEG data revealed that those in the social-exclusion group had clear differences in activity in the brain's occipital, parietal and prefrontal cortex regions. Those in the social-exclusion group also performed more poorly on the math questions. The inference is that social exclusion actually affects the brain's neural circuitry.

The parietal cortex is involved in attention, while the prefrontal cortex helps support so-called "executive functioning" processes such as working memory and other behaviors that may support self control.

"We found that there was a direct link between social exclusion, brain activity and performance," said Campbell.

One of the advantages of the MEG technique is that brain changes can be recorded in milliseconds, not in seconds, as some research of this kind may take. MEG actually has more advantages than other brain-imaging methods when it is used to look at real-time activity during a task.

The study may indicate why those who are never picked for athletic teams in pickup games tend to stay in that group and why those socially excluded sometimes react with inappropriate behavior or even violence.

The subjects in the UGA-San Diego State study didn't have clear or obvious reactions when they were told they would be alone later in life. Campbell said none of them seemed obviously upset or wept, for instance. At the end of the project, researchers told the subjects that it was completely untrue that their personality inventories showed that some of them would be alone later in life.

Bridget Jones winds up with her dream lover, as always happens in romantic comedies. The new research, however, shows that those who are socially excluded are more apt to show self-control difficulties, and might even wind up "all by myself."

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The research was supported in part by a grant from the University of Georgia Research Foundation.