Why We Buy (Behavioural Science In Marketing)

I’ve got a bit of a soft spot for behavioural science in marketing. Mostly because it reminds us of something very important:

People don’t make decisions logically.

Or at least… not entirely logically.

We like to think we do. We justify things after the fact. We tell ourselves neat little stories about why we chose one product over another. But underneath all of that? It’s emotion, bias, shortcuts, and a whole lot of subconscious nudging.

I was at The Marketing Meetup conference recently and two talks really brought this to life. One (from Phil Agnew) focused on how people make decisions, and the other (from Sam Conniff) on how people respond to uncertainty.

And together, they offered a pretty useful reminder: if we want to influence behaviour, we need to understand what’s actually going on in people’s heads.

Distinctiveness beats best practice

One of the first ideas that stuck with me was something called the Von Restorff Effect.

In simple terms: we remember things that stand out.

Which sounds obvious, right? And yet…

Marketing is full of brands copying each other. Same tone of voice. Same formats. Same ideas dressed up slightly differently. Particularly within a sector. Look at car adverts, watch adverts, perfume adverts. They’re all the same as their competitors.

It’s a fast track to being completely forgettable.

A good question to ask is: what about this would actually stick in someone’s mind tomorrow?

And if you need more guidance on being distinctive, check out this blog post on how to tell stories people actually remember.

Effort = value

Another idea I loved was how much we value things we’ve had a hand in creating.

This is known as the IKEA Effect. People place a higher value on things they’ve built themselves. In one study, participants were 63% more likely to pay more for furniture they assembled themselves.

Which is slightly mad when you think about it. Flatpack furniture is objectively more effort. And yet… we value it more.

You see this everywhere:

A bottle of wine with a cork (that you have to open yourself) feels more premium than a screw top.

Picking your own lottery numbers feels more satisfying than being assigned them.

Customising a product makes it feel more “yours”.

The takeaway? Involvement boosts value.

If your audience can interact, contribute, customise, or co-create (even in small ways) they’re more likely to feel invested in the outcome.

We follow others

Show people that others are buying, using, or recommending something, and they’re around 15% more likely to buy themselves.

This is social proof in action. Again, not surprising. But often underused. Or used in quite a flat way.

It’s not just about slapping “5-star rated” on something. It’s about making that social proof feel real, relevant, and visible at the right moment. Because when we’re unsure (which, let’s be honest, is most of the time), we look to others to guide us.

Small nudges, big impact

One of the simplest but most effective ideas shared was around input bias.

If something is labelled as a “best seller”, we’re more likely to choose it.

Not because we’ve done a deep evaluation. But because it reduces effort. It gives us a shortcut. It makes the decision feel easier and safer.

The same goes for autonomy.

If we feel like we’re making the choice ourselves (even if we’ve been gently guided there), we’re more likely to follow through.

No one likes feeling pushed. But we’re very open to being nudged.

And then there’s uncertainty…

Something we all experience but rarely talk about in marketing:

Uncertainty.

Because a lot of buying decisions happen in moments of uncertainty.

“Is this the right choice?”

“What if it doesn’t work?”

“What if there’s a better option?”

There’s actually research (including work from University College London) that looks at uncertainty intolerance: how comfortable people are with not knowing what’s going to happen next.

Some people find uncertainty deeply uncomfortable. Others are more able to sit with it.

People who regularly operate in uncertain environments, whether that’s entrepreneurs, performers, or even people in extreme real-life situations, often develop ways to work with uncertainty rather than fight it.

They don’t eliminate it. They navigate it.

What this means for marketing

As marketers, we often focus on persuading people.

But sometimes, the bigger job is helping people feel comfortable enough to decide.

That might mean:

Reducing uncertainty with clear, simple information

Building trust through credibility and transparency

Using social proof to reassure

Giving people a sense of control in the process

Or even just acknowledging the uncertainty in the first place. Because when people feel emotionally steadier, they’re far more open to taking action.

So what should we take from all of this?

A few things I’m trying to hold onto:

1. Different is memorable
If it doesn’t stand out, it probably won’t stick.

2. Get people involved
The more someone puts in, the more they value what comes out.

3. Make decisions feel easier
Use cues like social proof and “best seller” labels to reduce friction.

4. Give people a sense of control
Autonomy matters more than we think.

5. Don’t ignore uncertainty
People aren’t just making decisions, they’re managing how they feel about those decisions.

View from The Den

Behavioural science isn’t about tricking people.

It’s about understanding them.

Understanding that we’re not perfectly rational. That we’re influenced by what others do. That we value effort in strange ways. That uncertainty can hold us back. Or, if handled well, move us forward.

And if we can design our marketing with that in mind?

We’re not just pushing messages out into the world.

We’re actually helping people make decisions.