Whenever I speak at conferences, the delegates tend to fall into three categories. Those in a trance, those in a deep sleep, and those who are fully comatose. Only kidding. No, really, I am.

The truth is, there are those who sit up nice and straight, obviously eager to maximise their learning. Always bright and alert, I call them the sheep dogs. After those come the ones who are slightly sceptical about learning anything useful but are nonetheless willing to give you the benefit of the doubt. Often they lean backwards in their chair, surveying the room in the manner of a guard dog, just waiting for the occasional tasty tit-bit to be tossed their way. And then there are the mongrels. The cross between a hound and a St Bernard. They slouch in a slovenly manner and give the impression of not being interested in anything. Their body language tells you they really don't want to be there.

I remember from my school days that it wasn't cool to be seen sitting up straight and paying attention. In fact, if you wore two matching shoes you were considered posh. But apart from indicating your attitude to the situation and your willingness to take part, does sitting up straight and not slouching actually influence how much you learn? Does the way you sit at a sales meeting or a marketing conference make a difference to what you take away?

A new study by Pablo Briñol of Madrid university has examined how people's self-confidence and self-evaluation is affected by the pose they strike. He divided a class of students into two groups: half were told to slouch while the other half were asked to sit up straight. They were given some cover story about the experiment being concerned with curvature of the spine to throw them off the scent. These two groups were then split again, and half were asked to write down three positive personal traits about themselves, while the other half had to write down three negative personal traits.

The results showed that people who had been sitting up straight were much more likely to believe the positive things they'd written about themselves, whereas those who were slouching were much less sure. In short, their posture actually affected whether they really believed the positive or negative things they wrote about themselves. Proof that what you decide to do with your body position feeds back to your brain and affects your thinking.

So the next time you're at a conference or sales meeting, sit up straight, shoulders back, and no slouching. Because you won't just be giving the right impression, you'll probably learn a lot more too.

Philip Hesketh is a professional speaker on the psychology of persuasion and author of Life's a Game so Fix the Odds.