Influential language is important. Questions, listening and metaphor are important. But there could be an even more important factor in influence: the purely “incidental” behaviour of the people around you.

“Turns out your colleague’s husband’s sister can make you fat, even if you’ve never met. And a happy friend affects your happiness more than a bigger income. It turns out our connections – our friends, our friend’s friends, even our friends’ friends’ friends – have an astonishing influence on our behaviours, beliefs and even health.”

That’s the blurb from Connected by Nicholas Christakis and James Fowler, which sets out the science behind these surprising claims.

As I blogged recently, the infectious metaphors in people’s language, including their body language, provide one of the important ways in which behaviours spread through groups.

And there’s more to it than that.

Because behaviours can spread through networks of people even when there’s no intentional communication – and even no direct relationship – between the people involved.

Actions speak louder than words – and significantly louder than the small gestures which are  generally thought of as “body language”.

Here’s an example. I live very close to the Brentford football ground and yesterday, the team was playing at Wembley.

At one level, Wembley is a west London suburb about five miles away from Brentford. But of course “Wembley” has a much greater metaphorical significance than that – playing there means “We’re in the cup final!”

From early morning the street was full of flag- and scarf-waving, singing fans, joyously preparing to travel to the game together in a convoy of buses and coaches.

Now, I can honestly say that I couldn’t care less about football, and I’m sure the fans couldn’t care less about me. There was no intention to communicate.

But my heart filled with pride for my “local” team and I was almost tearful as the convoy departed, taking my good wishes with it.

The fans’ celebration was massively infectious. Their “metaphors” – waving flags and scarves, singing, shouting excitedly and all the rest – had a profound emotional influence on me.

A combination of what they were saying (singing, shouting) and doing (waving things) had an impact on my emotions…

And here’s the thing. One specific thing they were doing (waiting in a bus) influenced me at a different level. If I’d wanted to drive anywhere, I couldn’t get the car out!

There’s influence, and there’s influence.

It ties to a comment by Tim Ferris in my other favourite book of the moment, The 4-Hour Body.

Internet marketing guru Eben Pagan (aka dating guru David DeAngelo) asked him in an interview: “What’s the fastest way for someone to improve their inner game?”

Tim replied: “Improve your outer game.”

He explains: “The Cartesian separation of mind and body is false. They’re reciprocal. Start with the precision of changing physical reality and a domino effect will often take care of the internal.”

Where will you start?