There's an old joke about why grandparents and their grandchildren get on so well together. It's because they have a common enemy...

This might not be true of every family of three generations or more, but it does say something about the way people can come together and cooperate in defence against some perceived threat. And there's a paradox here relating to the question about whether competition "works" better than cooperation. Sports teams, political coalitions and international alliances are formed so that their members can together compete with an opposing group.

In sports, when the members of a team cooperate effectively with each other, the better they perform in competition with other teams. In warfare, well-drilled troops who work together usually win battles against loose groups, no matter how aggressive (competitive) their opponents may be individually. And one theme of politics today is to blame immigrants for our economic and social ills. Whether they really cause the problems or not, just like in multi-generational families, nothing unites like a common enemy.

Competition can be highly motivating. If you agree to participate in any kind of contest you usually want to win, because winning appeals to your need for self-esteem - to feel good about yourself. It's said we have a tradition in the UK (or at least in England) of respect the valiant loser. It's not the winnning, it's the taking part. I've never felt this. I don't seek conflict or competition in everyday life, but if I do join a competitive activity then I want to win - and I hate losing.

We all want to improve ourselves and to do better at what we do, and part of that is to measure ourselves against others. So competition is, in a sense, built in to our worthiest of instincts.

Now, competition isn't the only stimulus to greater effort and performance. Commitments made to others also motivate. Knowing that there's someone depending on you to play your part, to keep your promises, can really push you on.

I've got a compilation of "great poems" on CD and one of my favourites is The Listeners by Walter de La Mare. It's about a "Traveller" knocking on the door of a deserted house in the forest who gets no response from the ghostly listeners inside. It's mysterious and evocative - you wonder what brought him there. But the lines that always give me goosebumps are:

That phrase, "I kept my word", whilst telling us nothing about the circumstances seems to explain everything. You can understand why he's there.

A commitment made to someone else can be all-important. One of the worst things a sportsperson can do is to "let their team-mates down" by making a mistake or not trying hard enough. In post-match interviews you increasingly hear this as the prime motivator for an excellent performance. And in the extreme case of warfare, the same sentiment can lead individuals to sacrifice their own lives for the sake of their comrades.

But even what might look, on the face of it, to be pure selflessness can also be competitive! "I've done more than anybody else for this company / team / community", is to claim victory in the sacrifices contest. And that's important because it appeals to your strong need to be recognised, valued, or loved.

Cooperation has made our species a success. Learning to fight each other (like the ape-men at the opening of 2001: A Space Oddysey) didn't make us the dominant animals. Learning to act collectively did - the development of speech probably being the key enabler for sophisticated cooperation within the tribe.

I'm quite happy working alone. I love to solve problems all by myself. But working with others to achieve something that's beyond any one of us is really rewarding. And to keep your word, like the Traveller in the poem did, is particularly satisfying.

So what's the lesson in this for those of us who'll be voting in a couple of weeks' time? If no party gets an overall majority then no-one will be able to pursue their political agenda without regard to their opponents. Instead, there will have to be negotiation and compromise. A recipe for chaos, or at least for "weak government"? I don't think so. Having to reach consensus across different points of view surely leads to more sustainable results.

You and I benefit immeasurably from our ability to cooperate with others. So why shouldn't we benefit even more when politicians, acting on our behalf, use that skill as well?