How eating several smaller sized chocolates makes you look greedy and impulsive: the unit size effect of indulgent food

Imagine you are offered a package full of delicious chocolates. Would the size of the pieces of chocolate influences how much you eat?

Yes, the size of your piece of chocolate matters. This so-called unit size of food refers to the number of units in which a portion of food is divided. Earlier studies have shown that smaller units typically lead people to eat less. For example, Wansink and colleagues found that people being given four 100-calorie packs of crackers ate about 25% less than when given one 400-calorie pack. But why does this happen? Is it because everytime you start with a new piece, you realise you are still eating and wonder whether that is a good thing? A kind of pause moment? Or do other psychological processes play a role?

In a series of studies together with Hans van Trijp and Christos Kavvouris (published in Psychology and Health), we show that with a small unit size, people eat less because they have the impression (that others think) they eat more and are impulsive. Feeling or looking impulsive is something that many people want to prevent in our society.

Judging someone else eating chocolate (experiment 1)

In our first experiment, participants watched a movie featuring Michelle enjoying chocolate during a break. Half of the participants saw Michelle eating five small chocolates (about 50 grams in total). The other half of the participants saw Michelle eating exactly the same amount of chocolate, but now she ate one big chocolate bar. Interestingly, even though she ate the same amount of chocolate, participants considered the amount to be more excessive, impulsive and inappropriate in the case of the smaller pieces. 

 

Michelle eating 50 grams of chocolate in 5 small pieces (left) or 1 large piece (right)

 

Eating a fixed amount of chocolate (experiment 2)

In a second experiment, we asked one group of participants to eat all 5 small chocolates (50 grams) and another group to eat one entire large chocolate bar (50 grams). We asked them to imagine that they choose themselves to eat the amount they ate. Again, despite consuming the same amount of chocolate, eating smaller sized chocolates felt more excessive and inappropriate than eating one large piece.
 

Eating as much as you like (experiment 3)

Now participants got either 15 small-sized chocolates (150 grams) or 5 large-sized chocolates (also 150 grams) in a supposed taste test in which they were free to decide how much to eat. We also varied the wrapping of the chocolates (see picture below). Unwrapping a chocolate may draw attention to the decision to continue eating, which makes it less automatic.

About 23% less chocolate was eaten when it is presented in smaller units. Participants ate most in the groups being presented with unwrapped large chocolates. This unit size effect could be explained by people feeling more impulsive eating several smaller sizes chocolates than eating a large size chocolate.



Equal amounts of chocolate in the 4 conditions of study 3

Enjoy more, eat less
Across studies, the unit in which the chocolate was offered changed people's perceptions. Eating smaller units looks and feels more excessive and impulsive. Feeling more or less full had nothing to do with it. This brings us back to research on the numerosity effect in the 1990s. Essentially, we think that more pieces of something usually turn out to be more of something. In other words, bigger numbers equal bigger quantities. For example, a seven seater care is usually larger than a five seater car. A quick decision strategy that leads to good decisions most of the time, but it may also lead to wrong estimations.

Clearly, unit size is a cue that helps people to assess what an acceptable portion is. Smaller sized portions may help consumers to control themselves and eat less. Food companies could make item sizes smaller (indulgent snacks such as ice cream scoops or candies) or bigger (fruit, vegetables, whole wheat bread slices), depending on whether you want to make consumers effortlessly eat less or more.

van Kleef E., Kavvouris C. & van Trijp H.C.M. (2014). The unit size effect of indulgent food: How eating smaller-sized items signals impulsivity and makes consumers eat less, Psychology & Health, 1-41. DOI: 10.1080/08870446.2014.909426

What solutions do experts and students think of to get people to eat healthier? A summary of the Oslo workshop

This week I attended a workshop in Oslo in the beautiful building of the Norwegian Academy of Science and Letters. The aim of the workshop organized by our Food Ecology group of the Center of Advanced Studies was to come up with novel communication solutions to combat unhealthy eating habits. Guess what the typical ideas are that groups of participants came up with? First of all, apps and blogs are seen as a key solution to inspire consumers to change their behavior. The winning group came with an app for children that reward them for tasting new healthy foods. Other ideas were Facebook cooking pages and nutrition education campaigns targeting hard to reach consumers.

I admit that I am not objective, but I believe that our group came up with a very innovative nudge; a smart cap for sugary soft drink bottles that reduces the sip size. A study of Pascalle Weijzen and colleagues showed that smaller sip sizes lead to less consumption and quicker satisfaction. Our soft drink bottle concept also includes portion size indicators using clever sound and color sensors that indicate a suitable portion size. Enjoy more and drink less! However, one jury member called that 'a fantasy' and another jury member worried about Norwegian consumers traveling to Sweden to purchase cheaper soft drinks. Too bad...

Interestingly, when people are asked to come up with solutions, they first of all seem to think of the educational route to persuasion. This may be obvious, but Walls and colleagues wrote in their paper called 'Why education and choice won't solve the obesity problem' in the American Journal of Public Health: 'Although education and access to information are fundamental rights and are important in a democracy, they have a negligible impact on obesity'.

Anyway, it was fun to see how education is like the first intuitive way to go, even though it is getting more and more clear that focusing solely on increasing people's knowledge will not be sufficient in changing eating habits.

De invloed van calorie- en beweeginformatie op hoeveel je eet: Noraly Duizer's presentatie tijdens Student Research Conference

 Afgelopen week had Noraly Duizer de eer om haar bachelor thesis te presenteren tijdens de Student Research Conference (SRC) te Amsterdam. Op de SRC presenteren geselecteerde studenten hun bacheloronderzoek. Hoewel Noraly niet in de prijzen viel ging haar presentatie erg goed.

 

Afgelopen voorjaar gaf Noraly aan 148 deelnemers een portie chips met daarbij op de verpakking gemanipuleerde informatie over het aantal calorieen in een portie en hoe lang je moet sporten om deze calorieen te verbranden. Heeft deze informatie invloed op hoeveel mensen eten en hun concrete sportplannen? Maakt het de chips juist lekkerder en het schuldgevoel na het eten groter? Lees het in de paper van Noraly hieronder!

 

 

Portiegrootte bepaalt sterk hoeveel we eten; of het nu komkommers zijn of chips

Kinderen worden in ons land steeds zwaarder; ongeveer 1 op de 8 kinderen heeft overgewicht. Dit komt niet alleen door te weinig beweging, een belangrijke reden is ook dat we steeds grotere porties eten. De laatste decennia zijn portie groottes van veel voedingsmiddelen gegroeid. Een voorbeeld is de familiefles Coca-Cola die in 1957 werd geïntroduceerd in ons land. Deze fles bevatte maar 750 ml cola. Nu bevat een familiefles het dubbele of zelfs 2 liter. Dit fenomeen is ook te zien bij plakjes kaas, zakken chips en bakjes friet. Als consumenten houden we van ‘waar voor ons geld’ en fabrikanten en restaurants gaan hier op in door grotere porties aan te bieden. Onderzoek heeft echter laten zien dat mensen helemaal niet zo goed zijn in het bepalen van wat een normale portie is. Wat op ons bord of in de verpakking zit eten we voor 95% op. Het blijkt dat we dit teveel aan eten meestal niet compenseren door later minder te eten. Dit wordt ook wel het ‘portie grootte effect’ genoemd en is een belangrijke oorzaak van het overgewichtsprobleem.

Maar wat als we dit ‘portie grootte effect’ gebruiken om kinderen meer groente te laten eten? Groente bevat vitamines, vezels en is van nature ‘light’, maar kinderen eten er, net als veel volwassenen, te weinig van. Ga je ongemerkt meer eten als je meer krijgt, of stop je omdat je vol zit of je het niet meer lekker vindt? Deze vragen waren, kort gezegd, de aanleiding van de ‘komkommerstudie’ waarin 255 kinderen van de basisscholen de Springplank in Rhenen en de Koning Davidschool in Ede aan hebben meegedaan. Ilse Bruggers heeft de studie uitgevoerd als haar afstudeerproject, begeleid door mijzelf en Emely de Vet.

Hoewel een koekje de populairste schoolsnack bleek te zijn (bijna 77% van de kinderen gaf aan koekjes mee te nemen naar school), namen alle kinderen enthousiast deel aan de studie. ‘Ik vond het heel leuk en lekker! Kunnen jullie de volgende keer terugkomen met aardbeien?’ schreef een 9-jarige meisje op de vragenlijst. Elke klas kreeg de komkommer op een andere manier aangeboden. In sommige klassen kreeg elk kind wel twee derde komkommer en in andere klassen een derde. We varieerden ook de grootte van de stukjes; sommigen kregen plakjes komkommer en andere een heel stuk. Er mocht net zo veel of weinig gegeten worden als je wilde; zelfs niets of alles opeten was prima. Na het invullen van een vragenlijst namen we de resten op het bordje weer mee en wogen hoeveel elk kind gegeten had.

De resultaten waren duidelijk; hoe groter de portie komkommer op het bordje, des te meer er werd gegeten. De kinderen aten gemiddeld wel 54% meer komkommer. Dat is al ruim 70 á 93% van de aanbevolen dagelijkse hoeveelheid groente voor kinderen tussen de 9 en 13 jaar. Of de komkommers nu in stukjes waren gesneden of niet had geen invloed op hoeveel de kinderen aten. De grote stukken komkommer maakten wel indruk; kinderen dachten dat ze meer gegeten hadden dan de kinderen die dezelfde hoeveelheid in plakjes voorgeschoteld hadden gekregen. Wat betekent dit nu in de praktijk? Als u wilt dat u kind meer groente of fruit eet, geef dan meer. Snijd het wel even in stukjes, dan hebben ze niet door dat ze er veel van eten.
 

Impulsive snacking at the checkout counter: nudging consumers towards healthier 'grab-and-go'-snacks

Candy aisle near checkout 

Tempting snacks placed right near the checkout counter can be hard to resist. Even though you know buying one is not in your best interest, they catch attention. These high-profit 'grap-and-go' snacks are particularly hard to ignore at the end of a shopping trip after making dozens of decisions. Even at my local shoe store, they tried to tempt me in buying candy (see picture).

In our recent paper published in BMC Public Health, we (that is Hans van Trijp, Kai Otten and myself) report two nudging studies on whether assortment structure and accessibility of healthier snacks influences consumer choices. The idea was that providing a larger assortment of healthier snacks and putting them on top of shelves makes these snacks more salient, attractive and convenient, leading hopefully to higher sales.

To test this idea, we first carried out a study among students in which we asked them to make a hypothetical choice from a shelf displayed at their computer screen. The results of this study showed that when the majority of snacks is healthy, students were are more likely to choose such a snack. Although this may seem obvious, they were equally satisfied with their choice and did not feel restricted.

However, lab studies do not always provide reliable predictions about how people behave in real-life. Therefore, we conducted a  field experiment in hospital 'De Gelderse Vallei'. We now put an actual snack shelf near the checkout of the staff canteen. Each week, an alternative snack assortment was on display. The assortment included either 25% or 75% healthy snacks. We also altered their place on the shelf (either on the higher shelves or the lower shelves). On completion of the study, we also conducted a brief survey among employees.

When 75% of the assortment consisted of healthy snacks, sales of healthy snacks were higher. In contrast to our expectations, putting healthy snacks at the most convenient (top) shelf space did not impact consumer choices and sales. It could be that our manipulation was not strong enough (see picture). Interestingly, the majority of surveyed employees did not notice assortment changes. When asked, however, they preferred the shelf displays including the larger variety of healthy snacks.

Overall, these studies show the size of a healthy assortment of snacks matters. A relative large assortment of healthy snacks is able to influence consumer choices. However, we do not know whether this intervention really leads to better snacking habits at the longer term. Moreover, these types of interventions are typically more successful in canteens than those in restaurants and grocery stores, where financial interests are at stake.  


While not all nudges are effective (see for example our nudging study among children), this nudge might be worth to give a try. Without forbidding any foods, a larger assortment of healthy snacks may catch consumer attention and even seduce them to purchase. 


Nudging paper in BMC Public Health: Healthy snacking at the checkout counter: a lab and field study 


van Kleef E, Otten K, & van Trijp HC (2012). Healthy snacks at the checkout counter: A lab and field study on the impact of shelf arrangement and assortment structure on consumer choices. BMC public health, 12 (1) PMID: 23231863

A nudge that did not work: a virtual supermarket study among children to promote healthier snacking

Nudging consumers towards healthier food choices is still a hot topic. Drawing on psychology and behavioural economics, nudges are simple intervention strategies to move consumers towards healthier choices. This is done without banning foods products or telling consumers what to eat or avoid.

There are quite a few examples of successful nudges that help consumers in making better food choices. For instance, if consumers were asked to downsize their side dish, they ended up eating less in the study of Schwartz and colleagues. Still, there is a lot of debate about the usefulness of nudging. Consumers need more than a nudge, is the argument put forward by Lucy Handley. Lord Krebs recently argued in the Guardian that nudging alone will not convince people to do important things like lose weight. They both might be right, but at the same time I think it very useful to collect empirical evidence on the effectiveness of nudging.

Last Summer, we carried out a nudge study among 113 primary school children (10-12 years old) to encourage them to go for a healthier snack. We were inspired by the proven marketing tactic to offer a free gift with purchase (think of McDonald's Happy Meal). Typically, children are confronted with these free gifts on energy dense snacks. But would it be effective to use this classic marketing tactic to encourage children to switch to something healthier? That was the key question in our virtual supermarket study on which Charlotte Petri graduated last August.

We asked children to do some groceries in the virtual supermarket and select their own snack and drink near the checkout counter. This simulated supermarket of Wageningen University looks like a real supermarket with various shelves which display three-dimensional images of a wide range of products. The children could walk through the aisles of the store and put products in their virtual shopping cart.

Participant chooses a snack in the virtual supermarket

Participants did not see the same snack shelf, however. One third of all participants were confronted with a shelf poster that promised them a free gift (a tattoo) when they would buy a product with a star. These 'star products' were all healthier options as indicated by the Dutch Nutrition Centre. Another group were similarly promised the same gift, but now the star was attached to relative unhealthy snacks. The third group was the control group who did not get to see any promise of a free gift.

Snack shelf with poster promising free tatto gift with healthy 'Star' purchase

Most children were very enthusiastic about 'shopping' in the virtual supermarket ('Where can I download this game?'). Less than half of all children selected a healthy snack and drink. They were, however, not influenced by the promised free gift, regardless of the type of product to which the star was attached. It could be that the gift was not attractive enough, although a pre-test indicated differently. Another explanation is that children might have been too focused on the shopping task. In other words, they were too 'busy 'walking' through the shop, impressed by the new experience.

About one fifth of all participants was overweight. This percentage is similar to the percentage Dutch children who is overweight. Although overweight children more often tended to go for unhealthy snacks, they were not more sensitive to the free gift than normal-weight children. Children chose snacks based on familiarity and preference. Health was less important in their choice.

Overall, although the nudge was not effective in its present form, we learned a lot about the possibilities of the virtual supermarket for choice experiments with children. Have a look at the video, in which a participant walks through the supermarket and makes her snack choice.

Wanting to eat healthier, but little healthy foods sold at McDonalds

Most fast food restaurants do not share their sales data of healthy foods, but that did not stop Lyndall Wellard and colleagues to find out how many healthy items are actually sold at the biggest fast food chain in the world. They observed what people bought at 20 McDonalds restaurants in Australia. Of the 1449 meal purchases observed, only 1% could be considered healthy, 65% were unhealthy and 34% were take-away (so impossible to determine whether food is healthy or not).

Only 1% of all meals eaten in the restaurant! That is not much... Why would you sell healthy foods in a restaurant when hardly anyone is buying it? As a service to the 1% die-hard dieters who really do not want burgers and fries? Or to create a healthier image which may lead to higher overall sales?

According to a survey among Americans, 47% said they wanted restaurants to offer healthier items like salads. Even 23% said they tend to order those foods. Apparently many consumers like to have these items on the menu. Maybe as a license to indulge? Research of Wilcox and colleagues already showed that adding a salad or fruit to the menu makes you more likely to order fries. And to make it worse: consumers also tend to believe that adding a healthy item to a meal magically decreases the number of calories of the total meal.

In my previous blog post, I discussed the essay of Marion Nestle and David Stuckler on the influence of large food companies on public health. They are right, healthier foods are inherently less profitable. At least when eating out, most consumers seem to just want to indulge (without feeling too guilty).

Have a look at the new virtual supermarket of Wageningen University

In the video below, Erica van Herpen (my colleague at the Marketing and Consumer Behaviour Group) explains the advantages of doing research with the virtual supermarket. This simulated supermarket looks like a real supermarket with various shelves which display three-dimensional images of a wide range of products. As a consumer, you can walk through the aisles of the store and put products in your virtual shopping cart. The virtual supermarket allows us to easily manipulate various types of choice environments and promotion techniques. Interesting shopping patterns can be tracked, such as the time spent shopping or looking at a particular shelf, the number of products bought and the amount of money spent.

As reported in a previous blog post, we are currently working on a nudging project. Nudges are simple, low-cost interventions to move consumers towards healthier choices without banning food products or telling them how to live. According to what many consumer say themselves, health and sustainability are key reasons to select a certain product. In practice, however, this does not always appear to be the case. How can we best help these consumers in making the right choice by changing the shelf lay-out of healthy and sustainable products in supermarkets? Our new virtual supermarket is now used to study choice environments to stimulate healthier and more sustainable food choices.

Keep an eye on this blog, I will update you about new study results obtained with this exciting and innovative research tool.

Six principles of a good Choice Architect - inspiration for nudging consumers towards healthier food choices

Nudging is hot, as I described in an earlier blog post. Nudges are simple, low-cost interventions to move consumers towards healthier choices without banning (food) products or telling them how to live.

A freely available paper of Richard Thaler, Cass Sunstein and John Balz sketches the six principles of good choice architecture. A choice architect has the responsibility for organizing the context in which people make decisions.

The principles in the paper form the acronym NUDGES:

• iNcentives - make consumers aware of the incentives they face. For example, make the costs saved of certain things salient, such as the cost per hour of lowering the temperature a few degrees or the calories burned by doing certain activities.
• Understanding mappings - help consumers to improve their ability to map and hence select options that will make them better off. For example, make information more comprehensible and transparent (which is absolutely not the case with costs of mobile phone use or credit cards).
• Defaults - a large number of people end up with the default option, the choice that you will get if you do nothing. Changing the defaults regarding the way food is served and presented could also change consumer choices for the better.
• Give feedback - provide feedback on the performance of people (clever feedback systems).
• Expect error - leaving the gas tank cap or bank card behind when done are examples of such predictable errors. This is called the 'postcompletion error'. As consumers make mistakes, a well designed choice architecture assumes that people make mistakes and takes this into account.
• Structure complex choices - consumers are likely to go for a simple choice strategy when decisions are complex. So, the more complex a decision is, the more choice archictecs have to do their best to structure and organize the options.




Nudging study: changed default snack assortment



These principles are an inspiration for empirical research into nudging consumers toward healthier food choices. At the staff canteen of a Dutch hospital, we recently changed the default assortiment of snacks (both healthy and unhealthy snacks) and measured how much we sold. Student Kai Otten will soon reveal the results of this interesting field study. Keep an eye on this blog.

More student nudging projects can be found at the page of this blog called 'Student thesis info: do consumer research yourself'.

Eye tracking studies done by our research group on Dutch television

Last Tuesday, the Dutch television show 'Altijd Wat' paid attention to the debate on how to best inform consumers about making a healthy choice in the supermarket. Increasingly, information about the healthiness of a food is put front of pack in the form of a logo or health stamp. These logos are supposed to make your healthy choice more intuitive and easy.

But do consumer see these logos and labels in the midst of other information on the package? And to they use them to make a healthier food choice?

To get insights into which elements at a food package really attract consumer attention, Erica van Herpen and Hans van Trijp use eye tracking techniques. An eye tracker is a tool for measuring how the eyes move over an object (such as a food package) and at which point they stop to focus. Their latest paper on this topic examined which type of nutrition label attracts most attention, even when consumers are under time pressure (as we often are in the supermarket).

Watch Hans and Erica in action while demonstrating the eye tracker (item starts after about 10 minutes).

Are you thinking too much or too little about food?

I came across a really good paper of Dan Ariely and Michael Norton about the fascinating research being done in human decision making: 'From thinking too little to thinking too much: a continuum of decision making'.

Basically, there are two approaches to thinking; on the one end of the extreme someone is thinking too much and too carefully. On the other end of the extreme someone is thinking too little; a thinking style based on intuition, heuristics and quick short cuts. Both thinking too little and too much can have negative consequences and lead to mistakes, they argue.


More ice-cream options is definitely better... 

Thinking too much makes decisions harder or leads to postponing them. They refer to the famous study of Iyengar and Lepper who showed that grocery shoppers who were offered free samples of 24 jam flavors were less likely to buy any jam at all than those shoppers who sampled only 6 flavors. This clearly shows that considering too many options made it too hard to choose one. Barry Schwartz calls this 'the paradox of choice. Why more is less' and argues that we are faced with far too many choices on a daily basis. Nevertheless, Iyengar and Lepper's study also showed that people given more options enjoy the process of choosing. That is what I recognize when looking at my daughters in an Italian gelateria. They love to take their time to make a decision, although they typically end up with the same familiar strawberry flavour.

Dieters tend to think a lot about eating, particular negative self-thoughts. Their long history of going on and off on diets and guilty thinking patterns makes them more likely to overeat when confronted with tempting foods. Clearly an example of thinking too much, with harmful consequences. That is because their thinking is too 'concretely' and too much about the struggles of the moment ('shall I take the apple or the chocolate cake?). This uses up a lot of self-control in contrast to thinking about long-term goals (such as being fit and healthy) which can enhance your self-control. This finding came out of a study of Fujita and Han in Psychological Science.

Relying on habits ('I have always done it in this way') can be harmful as well. For example, out of habit, people tend to eat the entire portion that is served to them, even when it is stale popcorn. A little bit more thought could be good in that case. In other words, you may miss out opportunities to eat healthier when you often make quick decisions out of habit.

In an interview, Norton concludes by saying: 'What we know now is that people sometimes think too much, and sometimes they think too little. But we still don't know the right amount to think for any given decision, which is a fascinating decision yet to be solved.'