...in one interesting study, a group of researchers led by Roy Baumeister at Florida State University found that if you made people feel socially isolated..., it would decrease their sensitivity to the plight of those around them. To demonstrate this, they created a clever (though somewhat harsh) experiment. They had participants complete a bogus personality questionnaire and then told some of them that, based on the results, they were the type of person who most likely would not be able to develop meaningful relationships later in life and thus would end up alone....
Turned out that the people led to believe that they would become socially isolated did indeed care less about [others]. Not only that, it also made them less likely to engage in any prosocial behavior in general, and even made them less sensitive to emotional and physical pain. In short, it numbed them. It seems that when the possibility of developing beneficial long-term relationships is removed, either because the person in need doesn't appear to be the type of person who is worth your efforts (i.e., is dissimilar to you) or because you have reason to believe that you are unlovable and so your efforts would be fruitless, ... your impulse to care about the suffering of others switches off. If you can't count on anyone besides yourself, you might as well live only for yourself, right? [Desteno & Valdesolo, Out of Character, 147-148]
This research suggests that socially isolated individuals would be more receptive to the idea of living only for oneself. This could mean one of two things when related to Objectivism: (1) it could mean that Objectivism would appeal to social isolated individuals; and (2) that Objectivism has a built-in incentive to make people social isolated, since this will increase the chances that this individuals will accept and remain true to the Randian creed.
Let's first examine the appeal that Objectivism might have to the socially isolated. One issue that Objectivists tend to be naive about is the degree to which ideologies are, in a sense, self-selecting. That is to say, people tend to choose ideologies, not because of the acceptance of some premise or the logic of some argument, but because that ideology appeals to their needs, desires, and/or weaknesses. Generally speaking (there may be exceptions), people don't become Objectivists because they are convinced by Rand's premises or arguments; rather, there is something they find emotionally appealing in Objectivism, which leads them later to adopt a speculative allegiance to Rand's premises. Rand's philosophy strikes them as true and enlightening, despite the absence of sound argument and compelling evidence.
Now there may be any number of factors that draw individuals to Objectivism beyond social isolation. But it does not seem implausible to suggest that a socially isolated individual will more likely be drawn to Objectivsm than individuals who are better integrated into society.
However, it's also possible that the causation might flow in the other direction: that rather than being socially isolated to begin with, Objectivism may encourage people to become more socially isolated over time, which then reinforces their commitment to Objectivism. There are reasons to believe that this might be the case in some instances. In recent posts, I've been emphasizing the lack of social virtues in Objectivism. While Rand was not necessarily opposed to such values, her refusal to emphasize them (and sometime to write in a way that may suggest, to some readers, disparagement or indifference to them) could have a bad influence on those intensely drawn to her philosophy. I would also note that Objectivism doesn't always have the best record for providing social support to its members. The worst example of this on record involves Ellen Plasil, who was ostrasized by the Objectivism community (and ignored by the Objectivist elite) after she exposed the wrong-doing of "Objectivist" therapist Lonnie Leonard. But there are other examples of anti-social behavior, not only in the behavior of at least some Objectivists online, but even in the behavior of Objectivist elites, including Rand and Peikoff. Rand wound up breaking with nearly all of the original Objectivists who made up her inner circle in the fifties and sixties. And Peikoff has continued that tradition; indeed, he has even admitted to being "on terms of personal enmity" with "a few longtime [ARI] Board members." Why is it that at least some Objectivists struggle to get along even with other Objectivists? To be sure, getting along with other people can be a huge challenge. But that is precisely the reason why social values need to be emphasized. Those who understand and appreciate the limits of human nature realize the need for a kind of chivalry in human dealings. We're not always going to see eye to eye with those around us. People have different desires, tastes, emotions, sentiments, and values, so conflict is inevitable. But as long as we don't always assume that our own personal values represent some kind of gold standard applicable to everyone (despite innate differences in temperament and environmental differences in circumstances), it becomes much easier to tolerate differences in others. After all, we can't be at open war against everyone who thinks differently from ourselves. Freedom requires a certain degree of tolerance. It means allowing other people to think and act in ways that may go against our own deepest convictions. Being at open enmity not only with the world at large, but even with individuals in one's own clique, is hardly a wise way to live. It encourages precisely those elements in human nature that lead to social isolation and intolerance. It's not clear that a free society can exist among intolerant, socially isolated individuals.