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Why your grocery shopping is never cheap

Updated: May 17, 2022

I would be sincerely surprised if you have never walked out of a supermarket with more in your hands than what you came for. Perhaps you just walked in to get some milk and cereal, but along the way you picked up that new type of coffee that was on sale at the end of the shelf. After all, the milk was all the way in the back of the supermarket, and there were many really lovely, colourful items that called out to you. You were also in a bit of a hurry, so when you got to the cereal aisle, you just reached out for the Kellogg's even though you usually go for the cheaper store-brand. But hey, it was right there on the middle shelf. Perhaps while walking towards the checkout, you even picked up a chocolate bar. They're not too expensive, and at this point you were feeling a bit hungry.

Well, if this could be you, you've felt the power of carefully curated choice architecture, which is psychologist-speech for the more popular term 'nudging'. That is, you've experienced how environments encourage you to make certain decisions, and not others, and your quick trip to pick up breakfast became more, perhaps much more, expensive than planned. For nudging is about making certain decisions easier or more attractive, resulting in you being much more likely to engage in whatever behaviour its designers wanted.

Despite having studied why and how such influences work, I fool for the same tricks as everyone else. Should I know better? Maybe. But having knowledge is often not enough.

Why nudging works

What nudging traditionally is thought to rely on is what the Nobel Prize winning psychologist Daniel Kahneman called System 1 thinking (1). System 1 thinking is intuitive, quick, and very helpful in navigating our everyday lives without overworking our brains from all the decisions we need to make. System 1 thinking doesn't require much (if any) conscious effort. It's instinctive. You therefore don't need to consider which of two items are the furthest away, or if to stop for a red light. Really, it's all automatic. This is opposed to what he calls System 2 thinking, which is the slow, deliberate process required e.g., to park in a narrow space, or to solve a math problem (given its more advanced than 1+1 = ?). If it we had to use System 2 in order to pay attention to everything we encountered, we would be immensely tired from all the effort we would have to put into every little part of our lives. We therefore really benefit from system 1 thinking, and conveniently, we are able to extend and apply this thinking across similar scenarios.

What nudging is doing is targeting such automatic behaviours. If the nudge designers desire to see a certain behaviour, they can make this behaviour the most obvious choice. You are then more likely to automatically engage in said behaviour. The UK government has since 2010 very successfully employed a behavioural insight team (BIT, or also known as the Nudge Unit) who has explored the use of behavioural insights in policy making. This team, led by David Halpern, has done experiments on how to get people to fill out their tax-return forms on time, save for their pensions, get off their sofa to vote, insulate their roofs, or cut down on household energy consumption (2).

What they developed based on this research was a strategy for behavioural interventions called the EAST framework. This is an acronym for Easy - Attractive - Timely - Social and describe the dimensions to target in order to promote certain behaviours over others. For instance, they found that by offering the service of emptying out people's attic, more people got their roofs insulated, despite the cost of this additional service (3). The hassle of sorting through everything was enough to keep a large proportion of people from installing insulation. This was despite the unnecessary cost of extra energy to heat the house and the invaluable cost to the climate by letting good heat go to waste. Simply making the job easier made more people insulate. Nudging using the other dimensions can have a similar effect. Take social, in my opinion the most interesting one. Making a behaviour social is utilising the fact that humans like to identify with a group. We have a desire to fit in – perhaps to avoid social sanctions, perhaps because we consider it part of our identity. This explains why providing accurate information about drinking habits among students as US campuses actually decreased drinking. Most estimated drinking rates to be higher than they actually were. By telling people drink rates are actually lower than perceived, people don’t feel the need to drink so much to fit in (4). Similarly, it explains why some people actually used more electricity after learning that they used less than the average in their neighbourhood: an undesired boomerang effect that taught us that norm-interventions can go wrong (5). When we learn what the norm is, people adjust their behaviour to fit that norm, for better or for worse.

There's much more to be said about the EAST framework, but a more recent model – the COM-B – has included the very relevant aspects of peoples capability and opportunity to engage in the desired behaviour (6). It is one thing motivating someone to do something, it is another thing making this outcome feasible. Think back to the most recent US election. Do you remember some controversy around closing voting stations and too few post boxes? Particularly in areas most likely to vote for the democrats. It could be, and indeed was, argued that no one was preventing people from voting. Everyone was still free to go to one of the big voting stations or find another post box. But the reason that this is more serious than it might seem is because it is targeting these very important dimensions of capability and opportunity, effectively making a certain behaviour more difficult, and therefore certain democratic voters less likely to cast their vote.

The evil twin of nudging

I suspect that we can all easily agree that the list above contains reasonably good causes, and in some sense this sort of nudging helps people to engage in a behaviour they already are keen on, but might not get around to doing. However, this voting-prevention stuff might cause you a bit of an itch. And rightly so, for it reveals to us the evil twin of the nudge, for which the ethical aspects should be of our concern. Nudges can be used for good and for bad. Some lovely, creative soul decided to call a bad nudge a sludge. And those are highly prevalent in our everyday lives too.

You might have noticed that terms and conditions boxes are always in really small print, in really small boxes? Have you ever read them? If you have, I bet it's only to be one of those edgy people who say they do. They are designed so you don’t read it, and going against that design requires persistence and resilience (or at least deliberate effort as characterised by system 2 thinking).

Or you have perhaps, like me, you’ve been persuaded to subscribe to the New York Times at the fresher’s fair (it's easy – pop your name, email and bank details and off you go), only to see 2 pounds leave your bank account monthly, which never stops because it requires a call to their international office? Perhaps, also like me, you've considered whether it would just be easier to wait until 2023 when your card expired, so you didn't have to deal with the hassle of unsubscribing.

In all fairness, I was a little inaccurate above. For a smudge is not only nudging gone bad. To be more precise a smudge is discouraging, instead of encouraging, certain behaviours which can be used both for good and bad. Making me waste my money on access to a newspaper which, as it turns out, I didn't read very much, is perhaps ethically questionable. But think of the anti-smoking efforts, which has led Denmark to hide cigarettes behind curtains or underneath the counters (7). Did the cigarettes magically disappear? No. But to a certain degree the demand did. By making it less visible, people became less likely to spontaneously engage in cigarette-buying. It is the exact opposite of what is happening when you place chocolate by the registers (everyone passes them, and your blood-sugar might be low), stack coffee on the shelf ends (studies has found a significant increase in purchases of products if it is placed visibly, the reason why producers will pay supermarkets generously to have their goods on display there) or put the on-brand items at the middle shelf (most visible and accessible). No wonder I always end up spending more than planned when grocery shopping.

However, the question both nudges and smudges should have us ask ourselves is this: Who decides what's good and bad?

Consider this a cliff-hanger. We would, after all, love to see you come back to our blog.

Signe Oehlenschläger Petersen

Blog lead of CUBISS

(Edited by Adam Shea, secretary of CUBISS)



(1) Kahneman, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux.

(2) Behavioural Insights Team (2014). EAST: Four simple ways to apply behavioural insights. Cabinet Office.

(3) Behavioural Insights Team (2013). Removing the hassle factor associated with loft insulation: Results of a behavioural trial. Department of Energy and Climate Change

(4) Lewis, M. A., & Neighbors, C. (2006). Social Norms Approaches Using Descriptive Drinking Norms Education: A Review of the Research on Personalized Normative Feedback. Journal of American College Health, 54(4), 213–218.

(5) Schultz, P. W., Nolan, J. M., Cialdini, R. B., Goldstein, N. J., & Griskevicius, V. (2007). The constructive, destructive, and reconstructive power of social norms. Psychological science, 18(5), 429–434.

(6) Michie, S., van Stralen, M.M. & West, R. (2011). The behaviour change wheel: A new method for characterising and designing behaviour change interventions. Implementation Science, 6(42),

(7) CPHPOST (2018). Danish supermarket to hide cigarettes.

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