Superadditivity: why diversity works

Despite well-meant intentions, organisations have made slow progress on diversity.

Ask CEOs why diversity matters, and you'll hear an answer along the lines of: "It's the right thing to do, and of course it makes business sense too." 

I believe leaders are being earnest with their response. In their gut, they know that diversity leads to better performance.

But if they're going to rouse and coax others to change, they'll need to find a more compelling argument. One that goes beyond intuition and actually explains how diversity leads to better results.

The first step for leaders is to get clear about the issue you're solving with diversity. Else we default to identity diversity as a muddled answer to a muddled question.

My interest is in how groups solve problems and make better decisions.  This points me to cognitive aspect of diversity. That is the unique set of "perspectives, heuristics, interpretations, and predictive models'' each of us brings to the party.

Interestingly, researchers have found that cognitive and identity diversity often correlate. After all, our identities shape so much of what we think and how we think.

The good news is that you don't have to look far to find the evidence to build a cogent case for cognitive diversity.

Big word, simple idea

To demonstrate the power of diversity, Scott Page, a University of Michigan social scientist, uses the concept of superadditivity.

It's a big word, but the idea behind it is simple. 

In a nutshell, superadditivity means that the whole is greater than its parts. 

Or put it another way, 1+1 = 3.

Here's an example of how superadditivity works. Let's say you've tasked two teams to solve a problem.

In Team A, you have two non-diverse experts. They possess a similar cognitive toolkit—their core beliefs, mental models and reference points. As a result, they're more likely to reach similar conclusions. You could express this as 1+1 = 1. 

And if they get stuck, they'll probably get stuck in the same place.

Team B has two diverse experts. With differing cognitive toolkits, they're more likely to come up with diverging conclusions. This gets you to 1+1 = 2.

The difference in their ideas may be small—all it takes is a slightly different perspective on what's possible. 

But here's the best bit: you now have the possibility to remix those two ideas to conceive a third option. Which is why 1+1 = 3. 

Diverse teams have greater propensity to discover what author Steven Johnson calls the "adjacent possible".

In Johnson's words: "The adjacent possible is a kind of shadow future, hovering on the edges of the present state of things, a map of all the ways in which the present can reinvent itself…[the adjacent possible] captures both the limits and the creative potential of change and innovation."

The right tool for the job

Superadditivity emerges when three conditions are met: 

  • the right domain 

  • the right problem

  • the right ability

Increasing intellectual breadth does not improve outcomes in all domains. Research shows that the greatest impacts are in solving problems, making predictions and creative ideation. If you happen to be a knowledge worker, you'll recognise that these domains make up most of the work you do.

The right problems are complex, difficult and multi-dimensional. With simple problems, ideas tend to converge, irrespective of how diverse the team is. And if the issue is unidimensional, solvable by a single expert, diversity becomes irrelevant.

Lastly, the right ability is essential. People often misunderstand this aspect of diversity. They fall into binary thinking, where increasing diversity comes at the expense of ability. Why choose between ability and diversity if you don't have to?

Instead think about diversity as a bonus. Say you're assembling a team for a new project. You've put together a shortlist of potential team members who have the right skills. If you then make choices which optimise for diversity, you unlock the bonus level. The crucial point is that all potential candidates have already met your ability bar.

In fact, Professor Page found that diverse teams consistently outperform non-diverse teams with higher ability individuals. The only conditions set were that: the problem was hard; the people were able; the selection pool was large enough to ensure sufficient diversity.

In his experiments, he would form two teams: one chosen at random and the other made up of the best individual performers. His counterintuitive finding was that Team Diversity almost always trumped Team Ability.

Not easy, nor quick

Increasing diversity can give you a performance bonus, but it requires a lot of work.

There's the culture trade-off. Organisations exert a lot of energy to create a sense of shared identity. The more diverse your workforce, the harder this becomes.

Here's a common fallacy: increasing diversity on its own will lead to better results.

Guess what? Getting 1+1 to add up to 3 is actually really hard. It also takes time.

Decision-making in groups is fraught with pitfalls. To earn the diversity bonus, you have to design team behaviours and norms to avoid falling into these behavioural traps.

Doing this also helps capitalise on the intellectual diversity that already exists in your teams. 

There are many simple tactics you can use. For example, to avoid groupthink in a meeting, ask everyone to prepare their thoughts in advance. To tackle the HIPPO (highest paid person's opinion) bias, ask the most junior person in the room to share their ideas first and keep going in reverse hierarchical order.

Dialling up diversity in an organisation is hard. Using that diversity to make better decisions is even harder.

But when you need to wrestle with the toughest problems you face, a cognitively diverse team is always going to give you better results.

Thank you to the Compound Writing members who reviewed this post: Mikko, Ryan, Yishi, Kushaan, Joel, Brendan and Johnson.