“But there hasn’t been a lot of research on how using a social network affects consumer behavior, particularly its effects on how people feel about themselves and the decisions they make offline,” said Professor Keith Wilcox.

Wilcox and Andrew Stephen (PhD ’10), of the University of Pittsburgh, conducted a series of experiments to explore how social network use affects consumer behavior. In one experiment, they told users to browse either Facebook or CNN.com for five minutes, then gave them a snack choice of either a cookie or a granola bar. They found that the more Facebook users focused on people they reported to be very close friends — rather than acquaintances or strangers (people they didn’t even know offline) — the more likely they were to choose the cookie more often than those who just browsed CNN. In another instance, users participated in an auction for a new iPad after browsing. Those who had focused more on close friends while browsing Facebook again displayed less self-control, as evidenced by higher bids on the iPad compared to those who browsed CNN. In addition, when users browsed Facebook and were instructed to share information with close friends instead of distant connections, they reported levels of higher self-esteem after browsing.

“People try to put their best faces forward on social networks and browsing for as little as five minutes can enhance users’ self-esteem and make them feel better about themselves,” Wilcox says. “The downside is that it results in an overinflated ego and manifests itself in negative behaviors.”

To further test the connection between social network use, higher self-esteem, and lower self-control, the researchers also conducted an online survey with more than 500 people nationwide. The survey results were consistent with their findings on self-control in the lab experiments — users who focused more on close friends than acquaintances in their networks had higher BMIs, were more likely to engage in binge eating, and had higher credit card debt and lower credit scores. The more time people spent browsing Facebook, the less discipline they displayed in their offline decisions.

However, Wilcox cautions that the potential negatives shouldn’t outweigh the positive benefits of engaging in online social networks. “Social network use can help people feel better about themselves, enhance their social capital, and help them build relationships,” Wilcox says. “The more people are aware of these negative tendencies, the more likely they are to counteract them.”

This research may also be applicable to advertisers, who have struggled with low click-through rates on Facebook ads versus higher click-through rates for ads on other sites like Google. “If people feel higher self-esteem and less disciplined while browsing a social network, advertisers might need to appeal to these users in a different way than they would on Google, for instance,” Wilcox explains. This creates a starting point for future research, he says, on the basis that consumers use social networks to fulfill a variety of social needs. Those needs include self-expression and self-presentation — some of the same needs that underlie decisions to purchase luxury brands and affect how consumers respond to messages promoting image versus quality.

On a broader note, Wilcox stresses the importance of recognizing how behavior rules differ online versus offline; in the real world, people tend to be more modest with close friends than with distant friends. But online, those social norms do not necessarily apply, he says. “If everyone on Facebook is sharing their accomplishments, it just seems natural to do the same thing — particularly with the people you’re closest to. But users should be aware that the high self-esteem they feel from sharing online can have a dark side.”

And that effect may not be limited to Facebook — Wilcox says it could hold true for any social network where people are focused on presenting a positive self-image. “Although LinkedIn is primarily used to develop one’s career, the heart of the network is about presenting a positive image to others,” he says. “And while some Twitter users focus on sharing news and other non-personal information, many also use it as a form of self-promotion.”

Keith Wilcox is an assistant professor of marketing at Columbia Business School.

“Are Close Friends the Enemy? Online Social Networks, Self-Esteem, and Self-Control.” Working paper, Columbia Business School, 2012.