When the reasons for the enormous success of Facebook are being listed, Mark Zuckerberg's coding skills are usually somewhere near the top.
But it's possible that another less well-known part of his studies also played an important role in the success of the world's most popular social network.
At Harvard, Zuckerberg registered for a double major in Computer Science and Psychology, and when speaking to students at Brigham Young University last year, he outlined the importance of psychology to Facebook.
"[What] is really important about psychology is that all these problems, at the end of the day, are human problems," he said at the BYU Tech Forum. "That's one of the core insights that we try to apply in developing Facebook... the things that people are most interested in are what's going on with the people they care about, and a lot of that information isn't on the internet today.
"It's all about giving people the tools and controls that they need, to be comfortable sharing the information that they want... A lot of what we are doing is as much psychology and sociology as it is technology."
Most of the discussion around social media has been on the technology that has made these networks successful — and the vast fortunes they have created for founders like Zuckerberg. However, there has been less focus on why we want to use them in the first place: the underlying psychology of social networking.
Research to understand our use of social networks is still in its early days. Even so, technology similar to Twitter and Facebook is already being incorporated into the business tools we use, and this inevitably has consequences for the way we behave at work.
Psychology and social networks
Our basic psychological motivation in using social networks is the same as face-to-face communication, says Professor Tomas Chamorro-Premuzic, professor of Business Psychology at University College, London. He believes conversations on social networks are linked to meeting three basic needs: affiliation (getting on with other people), competition (advancing your career, for example) and finding meaning.
In effect, social media is a large-scale digitised way of fulfilling these needs. The most interesting of these from a psychological point of view is finding meaning, says Chamorro-Premuzic.
"Social networks enable us to explore what other people are doing, what they are like," he told ZDNet. "It's the reason we can spend ages browsing through people's accounts, because there is a lot of information about people there you don't get in the real world. It's like a window into everybody's soul."
There is an element of voyeurism built in, and social networks are clearly aware of this and respond to it in different ways. Facebook, for example, won't let you see who has viewed your profile — although scam emails claiming the contrary still regularly do the rounds. LinkedIn, by contrast, wants you to upgrade to a premium account before telling you that information.
But understanding the detail of the psychological implications of social network usage is an ongoing project. Studies of 'Generation Y' users of social media suggest that for some, these virtual relationships are bigger, more intense and have more frequent contact than their real-world interactions.
Other studies suggest that different social media networks appeal to different Myers-Briggs personality types, though most of the major networks are so widely used that defining someone's personality from the social networks they choose is impossible.
There is even research that suggests a relationship between the number of social-media friends you have and the size of certain parts of the brain associated with social perception and associative memory.
How many friends?
In other ways, social media is little different from face-to-face conversation. For example, Facebook and other social media sites are often criticised for turning relationships into a numbers game, by implicitly suggesting the more connections you have, the better human being you are.
"A lot of what we are doing is as much psychology and sociology as it is technology" — Mark Zuckerberg
But psychology suggests that having more than a certain number of so-called friends is effectively meaningless, and that usage of social media hasn't enhanced our ability to make and retain friends. Most people have a core of five to 10 close friends, followed by a second layer of around 100 to 150 acquaintances who are still fairly relevant. Anything above that, Chamorro-Premuzic says "is just noise or just you trying to show status to others".
However, while we do not understand the intricacies of our relationship with social networks, our usage is not without its psychological risks, as Chamorro-Premuzic warns: "The danger is that people who get hooked have this narcissistic delusion... that people care about their tweets. The irony is more and more people are doing it, and nobody really pays attention to what others do."
Social media in business
All of this also goes for the business use of social networking, which is considerably behind consumer adoption. While the basic psychological motivations are the same, social media in the workplace is more complicated, in that use of it is increasingly obligatory.
For workers who have not grown up with social media this is a strain, and there are plenty of companies now offering 'social media for executives' training courses to teach CEOs when to tweet — and when not to.
Anecdotally, it seems that in business, people are far more comfortable collecting contacts in social media, even ones they don't know very well, in case they become useful later on. There's even the so-called LinkedIn Open Networkers group, who will connect with pretty much anyone to extend the reach of that network.
But social media in the workplace doesn't just mean tools like LinkedIn and Twitter: increasingly, social-media functionality is being built into business applications such as.
As the Salesforce website describes it: "Get to know your colleagues, see how influential they are, and see if they're online right now. Find and follow peers and experts to expand your network."
The idea of such tools is to make information flow more efficiently through an organisation. But implicit in this is that building your own brand — maintaining a profile, building influence — could soon be a key part of the day job, regardless of what industry you are in.
In many respects, what these social networks do is bring to light the power relationships that exist invisibly in every workplace. An ineffectual manager may find few people 'friending' him, while a bright junior exec may find many more senior managers following her updates.
This can be good for organisations and individual workers, in that it can highlight issues that might otherwise go unseen. But just as the gamification of your social life encourages some people to acquire as many 'friends' as possible, so the gamification of work could see our value as employees (rightly or wrongly) more tightly tied to our performance on these networks.
"The danger is that people who get hooked have this narcissistic delusion... that people care about their tweets" — Tomas Chamorro-Premuzic
What's measured, improves, as is well known — but just because it is possible to put metrics around the number of status updates made, or friends added, does that necessarily mean better business?
As Chamorro-Premuzic points out, being good at social networking is not enough in itself. "You can manipulate all these things," he said. "It's not a prime skill or asset on its own, but one of the things about any job anywhere in the world is that it will deal with people. So using these networks can be evidence of that skill."
Indeed, social media could skew business goals if not managed correctly, creating a professional narcissistic delusion instead of a personal one. We still don't yet understand the role of social media among consumers, so gauging its impact in the enterprise is even further away.
And for now, real-life relations still matter most, as Chamorro-Premuzic says: "Of course, a great deal of the networks and wheeling and dealings that underlie any business still happen offline. It's still your analogue or real-world connections that matter: but there is a great overlap between these things now."