Why 5:2 beats 80/80 in changing behaviour

Eighty degrees for 80 seconds. According to one tea manufacturer’s TV ad the secret to perfectly brewed green tea is the 80/80 rule – 80 degrees for 80 seconds.

I love that they are seeking to help people avoid turning their tea into a bitter experience but will creating a rule like this work?

A rule of thumb is best when it is unthinking

I’m fresh back from attending and presenting at a conference on the application of behavioural science to marketing. One of the points discussed was how we use rules of thumb (heuristics) to make decisions throughout our day.

The vice chairman of Ogilvy UK and keen advocate of behavioural economics, Rory Sutherland, made the point that marketers (and businesses more generally) can play a key role in creating and communicating rules of thumb to make adherence more likely.

Some examples of rules of thumb that you are probably familiar with:

• The 5:2 Diet
• Meatless Monday
• Dry July
• Movember
• Fish on Friday
• And possibly the most famous of all, the Sabbath

The beauty of these rules is they are straightforward – they are yes/no, either/or dichotomous choices. You either do or do not; there is no ambiguity about your behaviour. They are easy to follow because you don’t have to think too much about them. Eat normally five days a week and restrict your calories for two. Don’t drink alcohol in July. Eat fish rather than meat on Fridays.

In a world of choices and ambiguity, we respond to clarity and direction. As Rory noted, it is much easier to say you won’t drink alcohol two nights a week than it is to limit your consumption to 20 units per week. 

“Will I drink tonight?”, a yes/no question is easier than “How much will I allow myself to drink?” which requires willpower and self-regulation. Indeed, part of the challenge with 0.05 drink-driving campaigns is no one really knows what will get us to that level.

Similarly, it is more helpful to tell people to drink eight glasses of water each day rather than 2-3 litres because it makes it easier to follow.

The other benefit of these rules is that they are socially reinforcing. It’s easier to say you are doing ‘Dry July’ than moderating your alcohol intake for the month because other people know what the rule stands for.

Which brings me to the question of whether a rule like 80 degrees for 80 seconds will work?  I fear it is not easy enough to follow – it’s more like the 20 units rather than two days off type of rule. First, what is 80 degrees? The ad suggests adding water or letting the kettle cool down slightly, but who’s to know when the temperature is right? Eighty seconds is likewise something that requires monitoring.

The difficulty when you ask people to think about what they are doing is that it makes doing something harder. It requires us to expend mental energy and if the payoff is not significant, we’ll instead default to our habits or the path of least resistance. Give me a rule like 5:2 and I know what to do. Give me a rule like 80/80 and I’ll do it if I remember to think about my behaviour.

For your business, what rules do your customers use for consumer products and services in your industry? Can you make this rule more formal and use it to attract other customers? Is there a day, time or frequency that you can ‘own’ by creating a rule for it? And can you draw lessons from other industries in how they engage people to do (or not do) something?

Come up with a rule that’s easy to follow and you’ll be able to persuade customers to take action without them even having to think about it.

P.S. You can see the tea ad on YouTube here.

Bri Williams runs People Patterns, a consultancy specialising in the application of behavioural economics to everyday business issues.