Even if you're not a rugby fan you might be aware that there was a major upset in the early stages of the World Cup when "no-hopers" Japan beat the former champions South Africa in a pool stage match. Now the latter have some of the best players in the world and would have expected to beat a second-tier team easily. The fact that they didn't on this occasion shows that, in team sports, the whole is definitely greater than the sum of the parts - or rather in South Africa's case, less than the sum of the parts.

What Japan lacked in height, weight and skills, they more than made up for in strategy and discipline. A good plan and well-practised routines carried them through. And I bet they also had a major dose of team spirit: a sense of responsibility towards their fellows and a determination not to let each other down. Doing well for the team was the most important thing in each of their lives on that day.

Most of us want to be members of a group that gives us security and a common purpose. The sense of belonging answers a deep need and we sometimes repay that by working for the collective good. Not always though. If you're driven by a need to be valued by the other members of your tribe then you'll tend to look for things to do that make you stand out - not necessarily what's actually needed. You might think you're pursuing the group's goals but really, and often unconsciously, you're aiming towards your own gratification.

This often works itself out as you pass through the stages of Tuckman's model of group formation:

Forming
The members come together, not really knowing what to do and looking for guidance.

Storming
Personalities begin to assert themselves and arguments break out.

Norming
People are getting used to working with each other and are becoming committed to the group's goals.

Performing
Everyone now knows what they're doing and they support each other. Things get done.

I've watched and participated in this evolution many times. It's important for the leader to allow the stages to be worked through and not to push too hard at the beginning. Roles and relationships have to be settled before the team can work properly.

The four stages have been added to by different authors. One enhancement is the addition of a fifth stage, "dorming", where the group works so smoothly that it seems to require hardly any guidance. So it can go its own way and the welfare of the team becomes more important than its original purpose or goals. And the sense of attachment becomes so great among the team members that they don't want to let it go, even when the job is done.

Another problem that is often overlooked is the way that close-knit groups actively exclude others. As soon as a sub-group is formed within a larger organisation, those omitted will experience feelings about it: curiosity and ambition to join in or resentment, jealousy, and hostility. Or maybe just indifference.

Negative feelings about the group might stimulate competitiveness in outsiders and so motivate them to work harder (or so some managers believe) or they might lead to obstruction or sabotage aimed at the perceived elite. Even small acts or omissions, often committed unconsciously, can adversely affect performance. For example, noticing an error in something the team has done and not bothering to tell anyone about it.

If the outsiders are perceived as enemies then the effect can be to bring the group members closer together and their exclusivity is enhanced. Nationalism and xenophobia are what we call this in the wider world.

(And yet sportspeople can shake hands and congratulate each other after the match, which reveals a degree of mutual respect that is absent from other contexts.)

Now, we want to build teams and make them as strong as possible but it's clear that this strength has to be balanced by communication and interaction with others who aren't members of the team. Keep no secrets!

Also, ensure that everyone in the organisation has a "home team" of their own. If a number of individuals don't have a team determined by the organisational structure then they'll soon form their own - and you might end up with an "awkward squad" who are disenchanted with their lot and with management.

You don't need to be a senior manager to see these things happening or to influence them. But why should you go outside your narrow job description to make things better when your efforts probably won't be appreciated, or even noticed? It's easier to turn your back and then say, "I told you so" - but that way lies resentment and rage against the world.

It's better to influence things where you can by behaving openly and inclusively yourself. Doing what you can for the greater good, whether effective or not, is good for your emotional state. You can feel positive about yourself for doing the right thing even if no-one else acknowledges it.