A view from Rory Sutherland

Perspective: Why must agencies enforce one view of human behaviour?

Apparently, there are four fundamental forces in physics. Gravity, that's one. Then there's electromagnetism (two), the strong nuclear force (three) and the weak nuclear force (four). I think that's all.

Supposedly, a few theoretical physicists have tried hard to simplify things and reduce this to three or even fewer - by proving that gravity and electromagnetism are fundamentally the same thing, or something weird like that. But it seems they've failed because, for now, we're still lumped with four fundamental forces. Bummer.

On the other hand, marketers and marketing services folk are much cleverer than theoretical physicists. Because we can always narrow everything down to one force. For us, there's none of that shilly-shallying around with multiple influences. Stick with one - that's all that matters.

Of course, what that one force is varies according to who you are talking to. Talk to a designer and it's one damn thing, talk to a planner and it's something else. It might be "brand" or "loyalty" or "engagement". But it's always one thing. Life is so much easier when we act as though there were just one variable at work in influencing human behaviour. It's simple. In fact, the only downside with this approach is that it is such utter toss.

This peculiar marketing monism, which affects us all, is what leads to some of the worst misconceptions in our business. It means any two disciplines tend to view each other as competitive, not complementary. Anyone in an ad agency who suggests promotional activity is viewed as a heretic. It's a pity, because real business successes are usually the result of several psychological forces working in tandem. When, for instance, you produce really good advertising for Walkers crisps, but you also introduce loads of new flavours so they dominate the shelf space in the supermarket.

Now I don't know how many psychological forces are at work in driving human behaviour. But, at a scientific guess, I'd say "lots". There is the Earlsian Herd effect. There is choice architecture and framing. There is fame and saliency. Like the physical forces, some operate over great distances, whereas others operate powerfully only within a small radius of a decision. Remember, too, that your measuring equipment may not detect all forces equally - if your equipment is, say, people with clipboards asking fatuous questions in the street, brand preference may show up strongly but other, more contextual, influences won't register at all.

But we shouldn't let this pluralism bother us. If we acknowledged the existence of more than one force in human behaviour, we might end up in the same muddle as the physicists, wrestling with a near-complete and representative model of the universe. And then where would we be?

- Rory Sutherland is the IPA president and vice-chairman of Ogilvy Group UK.