Early in my career, I was working with a senior manager on an organisational initiative that required budget approval from a leader at our head office. The amount wasn’t large, but we needed the approval quickly. I drafted the email and sent it to my manager for review.

He looked at it, smiled, and instead of hitting Send, asked me to pull up a chair beside him.

Then he rewrote the email.

Here’s roughly what happened.

My subject line read something like “Request Budget Approval” — accurate, but it could have been any of a dozen emails sitting in his inbox that week. Nothing told the approving leader why this one mattered, or why now.

The body ran two paragraphs. I’d spent four or five lines explaining the initiative in detail — background, rationale, context — before finally arriving at the ask in the last two lines. I remember thinking it wasn’t badly written — I’d even reached for a dictionary once or twice to be sure I had the right words. But it was just backwards: everything the reader needed to act on was buried under everything I felt I needed to explain.

The Rewrite

My manager flipped the order entirely. The subject line named the decision, not the topic. The ask came in the first line. The explanation — that four-or-five-line justification — collapsed into a line and a half, just enough to answer the one question the approving leader would actually have. He bolded a few key phrases too — enough that skimming just those would tell the leader everything he needed to approve it. And it wasn’t dense text either — short lines, white space, nothing that made the eye work before the brain even started.

What had taken me two paragraphs to almost say, he said in about six lines. Same information. Same request. Completely different cognitive load.

As he typed, he explained why he was making each change. Thirty minutes after he sent it, the approval came through.

That surprised me.

The approving leader had a reputation for responding with a series of questions before approving almost anything. Yet this time, there were no clarifications. No back-and-forth. Just an approval.

At the time, I thought the manager had simply taught me how to write a better email. Looking back after years of leading programmes and working with senior stakeholders at clients, I realise he had taught me something much more valuable — he had taught me how to design communication for the way the human brain makes decisions.

Over the years, I noticed that some leaders consistently received faster decisions, quicker approvals and smoother alignment. It wasn’t because they had more authority. It wasn’t because they were more senior. And it wasn’t only because they had stronger relationships.

They understood — often instinctively — how to make it easy for the other person’s brain to say “yes.” Behavioural science gives us a useful way to understand why.

The Behavioural Science Behind How We Process Information

Our brains process information in two broad modes.

System 1 is fast, intuitive and effortless. It relies on patterns, familiarity and instinct. System 2 is slower, analytical and cognitively expensive. It questions, compares and delays until it feels confident.

Every important message nudges the reader towards one of these two modes.

When your communication keeps the reader comfortably in System 1, decisions often happen quickly. When it unnecessarily activates System 2, momentum slows. Now you’re competing with scepticism, competing priorities and limited cognitive bandwidth.

In my experience, five dimensions largely determine which path your message takes. The first two are entry conditions. Without them, the remaining three seldom matter.

1. Relevance

Before the reader consciously evaluates your message, their brain asks a simple question: “Why should I care about this now?” If that answer isn’t immediately obvious, you’ve already lost valuable attention.

Relevance isn’t about making your message interesting. It’s about connecting it to something your reader already cares about — a priority, a deadline, a risk, an opportunity or a decision they own.

2. Trust

The same words are interpreted differently depending on who sends them. When trust already exists, the brain spends less effort verifying every statement. When trust is weak, scrutiny increases automatically. (System 2)

Trust isn’t built inside the message. It’s the credibility you’ve accumulated long before the message arrives.

3. Fluency

Does your message feel effortless to read?

Not just grammatically correct, but visually clean, logically organised and written in familiar language. Research on processing fluency suggests that when something is easy to process, we are also more likely to perceive it as credible.

Ease of reading is not merely good writing. It’s a cognitive advantage.

4. Simplicity

Too many objectives. Too much context. Too many attachments. When readers have to hold several ideas in working memory, they slow down — or postpone the decision altogether.

One message. One objective. One unambiguous ask.

Simplicity respects your reader’s limited cognitive bandwidth.

5. Ease

Even motivated people avoid unnecessary effort. If the next step isn’t obvious, action gets delayed.

Reduce friction. Make the desired action almost automatic.

A simple reply. A single approval. One decision.

That’s often the difference between momentum and silence.

These five dimensions work together. Relevance makes the reader care. Trust lowers resistance. Fluency makes the message effortless to process. Simplicity makes it easy to understand. Ease makes it easy to act. It’s a domino effect.

Miss either Relevance or Trust, and the remaining three rarely get the opportunity to do their job. This isn’t about manipulation. It’s about respecting how busy minds work.

I think about that approving leader’s reputation often — the one known for a volley of questions before signing off on almost anything. That reputation wasn’t really about him being difficult. It was about how much System 2 scrutiny most emails forced him into: too little relevance stated up front, too little trust established in the writing itself, too much friction between his eyes and the actual decision. Most people who wrote to him were, without knowing it, inviting the very interrogation they dreaded.

My manager didn’t get lucky that day. He’d simply removed every reason for that leader’s brain to downshift into System 2. A sharp subject line. The ask in the first line. A line and a half of context instead of five. Nothing left to question because nothing was left ambiguous.

I didn’t understand any of that at the time. I just knew my email had taken two paragraphs to say what his said in six lines — and that his got a yes in thirty minutes.

Ironically, the lesson my manager taught me that afternoon was never really about email. It was about designing communication that works with the human brain instead of against it. And communication is more than 70% of what a leader does.

Looking back, I still think that will count among the most valuable leadership lessons I’ve ever received.