Why It Works: Creme Eggs and why we want what we can’t have

How do you eat yours?

Maybe this slogan is familiar to you. And it’s clever one at that – because it presumes it is inevitable that you will be eating a Creme Egg – the only question is how? But this legendary line is not Cadbury Creme Egg’s biggest marketing success.

No, what counts most is its availability. Or rather, lack thereof.

When Creme Eggs were launched in 1963 (then made by Fry’s), they quickly became an annual sweet staple.

And that’s half the magic, they are yearly treats. Released on New Year’s Day and only available until Easter, if you have a craving for a Creme Egg at any other time of year, you’re out of luck.

Creme Eggs became increasingly popular over the years. So popular in fact, that in the 1980s Cadbury’s decided to let customers have them year-round. You no longer had to wait until after Christmas to get your hit of sugary yolk.

Unfortunately for Cadbury’s, this change in availability caused sales to sag. Why? The answer lies in two psychological phenomena: scarcity and habituation. These are the true secrets to the brand’s enduring success.

The less we can have, the more we want

Cadbury’s is making textbook use of the scarcity bias, that is, we place higher value on things that are perceived as rare.

It’s a deeply embedded psychological phenomenon, and as such there’s evidence for it dating back many hundreds of years. My favourite historical example is the story of pineapples.

Pineapples are native to South America and the Caribbean and only arrived in England in the 1600s. Given the expensive and perilous journey they took to reach our shores, pineapples were extremely rare. And that’s why, much like a Rolex today, they became the ultimate symbol of status and wealth.

In fact, they were so revered that King Charles II had a portrait painted of himself being presented with a rather puny example of the fruit. Pineapples gained such prestige that people rented them as party pieces, paying the equivalent of an average week’s wage for the privilege.

What a wonderful example of how scarcity elevates the value of a thing. And, proving their status wasn’t driven by taste alone, once pineapples became abundant in the nineteenth century (due to the advent of steamships and refrigeration), their desirability plunged. We don’t sculpt decorative pineapples into our buildings anymore.

As well as countless strange stories like the pineapple, there is experimental evidence for this observation, including a famous 1975 study by Stephen Worchel, a psychologist at the University of Virginia.

He recruited 134 participants and asked them to evaluate the quality of a batch of cookies. Participants selected a cookie to taste from a glass jar that contained either two or ten biscuits.

The results were significant: even though the cookies came from the same batch when they appeared scarce, they were rated as significantly more likeable. In addition, participants were willing to pay 57 cents for them, compared to 46 cents for a cookie from the plentiful jar – a 24% increase.

So, anything in short supply clearly becomes more desirable. And this is a deep-seated and powerful influence on our behaviour. In fact, it’s one of the strongest biases, as evidenced by a review from Will Browne and Mike Swarbrick Jones from Qubit Digital.

Why It Works: How Elf Beauty uses behavioural science to power its growthLooking at 6,700 A/B tests among e-commerce sites, they found that scarcity was the most effective tactic for boosting average sales. Scarcity messages resulted in an average 2.9% uplift – the largest effect among the 29 message types tested.

These sites were using messaging, for example labelling offers as “limited time only” or “last few remaining”. But the same effect is triggered by seasonal availability. Low availability boosts desire. It’s about FOMO. Creme Eggs really are scarce, we all know we can’t get them for long, we’d better grab them while we can.

But there’s another psychological effect at play: habituation. Or lack of, in fact.

No time for boredom

Habituation is a psychological process that describes how people become less responsive to a stimulus after repeated exposure. In simple terms, when we experience something often, it loses its impact. The novelty fades, our emotional response weakens.

Any product that’s unlimited is at risk of habituation. And this is exactly what happened when Creme Eggs became available year-round. Consumers got used to them, and the sense of excitement and anticipation faded. Sales dropped as the product became just another everyday chocolate.

There’s good evidence that habituation has real impacts on behaviour. One study comes from Leif Nelson and Tom Meyvis at New York University. In 2008, they tested habituation to a pleasant experience, in this case, using a massage cushion.

Participants were split into two groups. One group received an uninterrupted 3-minute massage. The other had the same total duration, but their time was split into two 80-second sessions with a 20-second break in between. Afterwards, they rated their enjoyment on a 9-point scale (one = not pleasant; nine = extremely pleasant).

Why It Works: How McDonald’s applies behavioural science to sell friesThe results were clear: those who had a continuous three-minute massage gave an average rating of 6.05 out of 9. However, those forced to take a 20-second break during their massage gave a rating of 7.05 — that’s a 17% improvement in satisfaction.

The study shows that creating a break in a pleasant experience seems to reset people’s sensitivity to it. When restarting after a break, the massage feels fresh again.

This is exactly what’s happening with Creme Eggs. Only available for a few months of a year, the eggs don’t get a chance to bore us. There’s a limit to how many you can eat in a 3-month window. And so, we don’t habituate to the extraordinarily sweet gloopy centres.

Then we get a 9 month break from them so when the January release rolls around, we approach them as if they’re almost novel. We get that first-time high all over again.

This keeps us coming back for more year after year.

So, if you want to increase demand, ask, “should we make our offer rarer?” You could try limited runs, seasonal drops, or time-boxed offers to increase perceived value.

Or, copy Creme Eggs and create breaks in exposure, by rotating products, pausing campaigns, or staggering usage to prevent boredom.

After all, ‘How do you eat yours?’ only works because, for most of the year, the answer is: you can’t.