If you work in a UK ad agency, you can probably give yourselves a big pat on the back for the progress you’ve made towards creating a fairer, more inclusive workplace. There’s still plenty of work to do, but the long march to that fabulously exciting melting pot of genders, sexualities, abilities, ethnicities and nationalities is definitely heading in the right direction.

Then ask yourself how cognitively diverse you are as an organisation – how diverse in the way you think about, perceive and experience the world. Agreed, it’s a much harder thing to measure, but I bet you’ve got some people with a pretty far-out way of thinking about things.

Now consider how many were far out enough to, say, support Brexit. That should be every other person, if your agency is in any way representative of the cognitive diversity of the electorate. Is every other person you work with a Leaver? Is anyone?

Ah yes, but that’s not exactly a fair example, is it? There’s a self-selection bias in our industry. Marketing tends to attract open-minded, progressive, liberal types, not the sort of reactionary, swivel-eyed nut jobs who’d vote Leave.

The problem with that sort of thinking is that not all Brexiteers are reactionary, swivel-eyed nut jobs. That’s just a dumb stereotype that provides a pretext to dismiss rather than debate; to censor rather than understand. It crushes cognitive diversity and reinforces homogenising groupthink.

Irving Janis, the Yale psychologist who first described the theory of ‘groupthink’, defined the problem.

“The more amiability and esprit de corps there is among the members of a policy-making in-group, the greater the danger that independent critical thinking will be replaced by groupthink, which is likely to result in irrational and dehumanising actions directed against out-groups.”

But we’re in advertising. It would be crazy to suggest that we dehumanise people. Unless, perhaps, those people are the good half of the electorate who were swivel-eyed and nut-jobby enough to vote Leave. In a business whose function it is to communicate with the masses, it seems reckless – irrational even – to wilfully ignore what large chunks of the population are thinking and why they are thinking it. But we do it all the same.

So while we may all eventually work in fabulously exciting melting pots of genders, sexualities, etc, etc, it’s entirely possible for the same place to be a convergent intellectual monoculture that is dangerously unrepresentative of many of the people we’re trying to reach.

A huge part of the problem is the old adage that “we recruit in our own image”. Cognitive diversity suffers at the hands of recruiters looking for ‘a good fit’ (for which read someone who thinks like us) and recruitees suppressing their cognitive diversity in the hope of fitting in (for which read might have voted Leave but certainly isn’t going to tell anyone).

We are an industry that favours privilege and privilege is an homogenising force.

This doesn’t apply to everyone, of course, but we heavily over-index on private school-educated, top university/college-attending high achievers with strong networks, whose upbringing included things like foreign holidays, first cars and character-building extracurricular activities. How cognitively diverse can we really be if most of us came up the same way?

Sure, you may have worked hard to get to where you are today, but it’s easier to win the race when you start halfway to the finish line. As writer Helen Rosner tweeted in reply to Forbes’ latest “30 under 30” list, “all 30 Under 30 lists should include disclosure of parental assets”.

That’s not to say that the opinions of the privileged many are invalid. These are smart, gifted and committed individuals who are, very often, very good at their jobs. But the reason they’re good at their jobs is precisely because they’ve spent a lifetime on the conveyor belt of generational success, being efficiently trained to the task.

In his (properly excellent) book ‘Poverty Safari’, Darren McGarvey eloquently describes his own “botched attempts to move among the affluent … those in society who appeared to be doing much better than the rest of us, those who were gliding through life unimpeded by the constraints of poverty and the material disadvantage and self-doubt that comes with it” – and the profound resentment it caused when he found he couldn’t.

Our challenge is to find ways to draw people into the industry who haven’t been trained to the task. Those who have the talent but are held back by their personal experience and their lack of access to the tools. Those who might have kicked your arse if they’d started from the same line. Those who, on account of their different life experience, are cognitively – and welcomely – very different to the rest of us.

It’s not about worthiness or, worse still, charity. It’s about enlightened self-interest. Cognitive diversity simply makes us better.

Harvard Business Review recently completed a study that pitted teams of different cognitive diversity against each other. It found that the teams with low diversity “have limited ability to see things differently, engage in different ways … or create new options.” By contrast, the most successful teams were more diverse, showing “accelerated learning and performance in the face of new, uncertain, and complex situations.”

New, uncertain and complex is a pretty neat description of the future we face as an industry. We encounter existential threats from disruptive new technologies on a near daily basis. We need to adapt and, in some cases, completely revolutionise the way we do business, but it can be very hard to get individuals to understand the need for change when they believe their livelihood depends on them not understanding it.

The answer, of course, is to cognitively diversify – bring in people who understand these changes at a fundamental, instinctive level because they are a product of them. But too often ‘bring in’ means to build an archipelago of isolated practitioners or a ghettoised new specialism. And, too often, the acceptable face of change is only acceptable when it starts to think, walk and talk like the rest of us.

We’re well past the point where superficial makeover is going to get the job done. We need to completely re-engineer our DNA if we’re to overcome the phenomenal muscle memory of the traditional disciplines, adapt and survive. We need to set our agencies up, not to try and fathom the new world, but to think like it.

By failing to foster cognitive diversity, we hurt the work, diminish its effectiveness and expose ourselves to the risk of becoming obsolete. There is power in difference. We should embrace it in all its forms.