Wednesday, April 13, 2011

No dessert until you eat your vegetables!

As a child I had a love of sweets. Well maybe not just sweets, but junk food more generally. In fact one year I begged Santa for a bottle of ketchup at Christmas. Needless to say I didn’t get. Thanks Santa=( Like many parents, my Mom and Dad struggled to get me to eat full, balanced, healthy meals. I poked, prodded, and scattered the brown rice, fresh fish, and local veggies. I made many valiant attempts to trick my parents into believing I had consumed enough of the healthy stuff so that I could finally get to the good stuff, dessert.

So what do parents, like mine, do when they are faced with a ding dong craving, pringles loving, child like me?  If we look to classic psychology theory for an answer, the results are mixed. Research on behaviorism  has shown that positive reinforcement – when a behavior is followed by the presence of rewards – makes the behavior happen more often. Applied to the green veggie quandary - when children eat the healthy parts of a meal, parents provide rewards (e.g. smiles, stickers, or simply cold hard cash). If the theory is correct this will increase the likelihood the child will eat more healthy foods in the future.

This idea has been challenged by another line of research, however. Self-determination theory suggests that providing extrinsic rewards actually undermines, or diminishes intrinsic motivation. Again, applied to the green veggie quandary, if parents reward children for eating the healthy parts of a meal, children will actually come to like those healthy parts less, and will only be motivated to eat them, in order to obtain the reward. Take away the reward, and the green veggies will stay on your child’s plate. So who is right?

Researcher Lucy Cooke and colleagues at the University College London tested this question formally in their study of 450 4-6 year old children. Almost every day for a period of two weeks participants were asked to try a vegetable that they didn’t like very much. Dr. Cooke divided her sample into a few groups: the social reward group received praise from the experimenter if they tasted the vegetable, the external reward group received stickers if they tasted the vegetable, and the exposure group saw the vegetables but were given no reward. After this intervention period participants rated how much they liked their target vegetable and the researchers measured how many vegetables participants consumed when the rewards were no longer present.

What did Dr. Cooke find? Do rewards reinforce healthy eating like behaviorism tells us or do they diminish liking a la self-determination theory? In this study, children who were given rewards (praise, stickers) for eating a disliked vegetable ended up liking the vegetable just as much as participants who were exposed to the vegetable but were given no reward. In fact all of the groups came to like the vegetables more over the course of the study, simply through exposure to them.

The different groups didn’t fare equally well over time, however. Those participants who initially received rewards for eating the vegetable maintained a higher level of consumption even after those rewards were removed. In sum: kids who were given external rewards for eating their vegetables, be it stickers or praise, liked the vegetables more, and continued to eat them when they no longer received a reward.

These findings support classic research on behaviorism, and provide parents with some options when their child looks at broccoli and says yuck. Remember, participants liked and consumed more veggies whether they were given external enticement in the form of stickers, or social praise – “Brilliant – you’re a great taster!” Continue to expose your child to veggies, and when they taste them, clap your hands, cheer, smile! Perhaps you can reserve the sticker option for particularly unsavory looking foods. I know mushrooms gave me the heebie-jeebies as a child.

So what about no dessert until you eat your vegetables? It’s important to note that this research did not evaluate the efficacy of punishment, another tactic addressed by research on behaviorism. Negative punishment is when a behavior leads to the removal of something desirable. Many parents employ negative punishment - when they refuse to give their child something good, like dessert, if the child doesn’t eat something healthy first. Future studies should pit rewards against punishments in predicting liking and consumption of healthy foods.

 Although I still love a good bag of chips, and often indulge in a tub of ice cream, for the most part, I cook and thoroughly enjoy the very full, balanced, and healthy meals that my parents struggled to get me to eat as a child. How did I evolve into such a model of nutritional excellence? I suspect my parents continued to cook healthy foods, and when I was bold enough to try them, I got plenty of smiles and cheers.

What do you do when your child refuses to eat the nutritional (yet tasty) meals you slaved over? Did your parents do anything special that worked for you?

 Here's the article: 
Cooke LJ, Chambers LC, AƱez EV, Croker HA, Boniface D, Yeomans MR, & Wardle J (2011). Eating for pleasure or profit: the effect of incentives on children's enjoyment of vegetables. Psychological science, 22 (2), 190-6 PMID: 21191095


  1. Wow, very interesting. This is great reading material for my morning coffee. :)
    My son is almost two and I have to admit I have been very lucky in the sense that he has no problems eating vegetables. However, I have a feeling this will change at some point. Maybe when he starts to realize his cousins won't eat them? or when he starts to learn that as a kid he is "not supposed" to like veggies? Not sure but it would be interesting to see a study that says if kids at some point stop liking veggies. Is it a learned behavior? Also I never noticed until you mentioned it, but I have heard his father say the whole, "no yogurt until you eat all your food," etc. I would love to see more studies done on the negative punishment to see if it even works.
    However his father and I have different styles and I tend not to push my son to eat. I know that usually when he is hungry he will tell me and he will happily eat everything on his dish.
    So everyone has different styles but this again shows that positive reinforcment is effective. Good to know :)

  2. Thanks for your thoughtful comment. Though I’m new to this topic I found some interesting information on neophobia – the reluctance to eat new foods – which may help to address your questions (Dovey, Staples, Gibson, & Halford, 2008). Young babies seem to show little aversion to new foods – presumably because they are safely eating what their parent’s provide. Once they become mobile, children show a sharp increase in neophobia, when they are able to pick up and eat objects in their environment outside of their parents’ control, objects that could potentially be toxic. Neophobia peaks between age two and six, and then shows steady declines - likely when children are better able to decide what is safe and what is not. As you suggested parental and peer modeling do influence which foods a child is willing to try. For example, one study found that children were more likely to eat a new food when in the presence of a parent eating that food (Addessi, Galloway, Visalberghi, & Birch, 2005). This is great, if you, as a parent, eat healthy foods in front of your child. It could be problematic, however, if your child’s friends show aversion to healthy foods. Nevertheless, over time it appears as if this negative modeling is overcome, as children show a steady decrease in neophobia with age.

  3. Great information!!! Thank you so much for adding this! I had never even heard of neophobia before. That's so interesting.
    As far as modeling goes, we feed our son the same foods we eat every night, and we all sit down and eat it together. So I'm happy to know it's a good thing. Now I just have to get his Dad to stop drinking soda in front of him :)