Friends are important; they support you, listen to you, laugh at your jokes and have fun with you. Online they share information with you, point you in the right direction to useful material and support you with their feedback. There is little doubt that both online and offline friends are important. Indeed, for many years doctors have known that those of us with plenty of good friends tend to be the healthiest; friendship boosts our positive biochemistry helping our immune systems and protecting us from disease.

But your friends do more than this; they influence your thinking. Everyone you meet has some kind of influence upon you, but the people you have the most connection with are the ones who have the greatest power over you. New research on schoolchildren confirms that the attitude of those around us influences our feelings and our behaviour. The study from the University of Chicago showed that female teachers who believe that girls are no good at maths end up with girls in their class who - you guessed it - are not much cop at adding up. In other words they are passing on their anxiety to the children they teach, almost by a process of osmosis.

This research confirms many previous studies which show that our thoughts and feelings are often not of our own making. They arise as a result of the thoughts and feelings of the social groups which we inhabit. The whole notion of "group thinking" is an interesting one - how, for instance, do groups of people all think the same thing at the same time? They do. We seem capable of transmitting thoughts between us using all sorts of behaviours.

Online you can see this happening in places like Facebook groups. A thought, attitude or feeling takes hold and everyone in the group tends to think the same thing. It happens online with people who collectively support WordPress, for instance, all claiming that Blogger is garbage in comparison - and no amount of arguing can shift them. That's because unless the entire group changes its attitude, individuals are less likely to alter their opinion.

It all means that you are influenced heavily by the groups you get involved with online. Even in subtle ways they are affecting your thoughts, feelings, attitudes and online behaviour. This new research on schoolgirls shows us that we are open to influence not only in our thoughts but in the results of the way our thinking affects our behaviour. In other words, if you inhabit a group that suggests using a social network is tough, you will find it practically difficult. If we measured your knowledge and ability with social networks - and you have friends who tell you that social networking is difficult - then your results would be lower than people whose friends love social networking and say it is brilliant. In other words, your actual abilities in online technology are probably affected by the people who surround you.

It's the same with making money. The friends of millionaires tend to be millionaires. The friends of would-be millionaires are also millionaires. If you are poor and all your friends are poor - guess what? Yes, you remain poor. If you inhabit online networks that tell you blogging is a waste of time - guess what? You will find every excuse in the world not to do any blogging.

Your online friends influence you in many ways. Make sure you choose the right ones.

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