The first article in this edition of the newsletter explores the widely replicated

Decreasing dislike for sour and bitter in children and adults

Increasing children’s consumption of fruits and vegetables can be challenging for many parents. It doesn’t help that parents often use failed strategies. For example, many parents report giving their children a dessert to reward eating healthy food options in a meal, although only 7% of parents report that this strategy actually increases liking for that food. Some parents resort to forcing their children to consume healthier foods in a meal, often by having their children sit at a table until they have “cleaned their plates.” This also produces a negative outcome; children generally report greater dislike for foods they are forced to consume. This article focuses on an alternative learning strategy that parents can use to increase consumption of fruits and vegetables: flavor-reinforcement learning. This method not only works, but is also a practical strategy for parents.

Increasing Liking By Making Foods Taste Good!

Why won’t some children and adults eat fruits and vegetables? One reason is that some fruits are sour (e.g., grapefruit) and most vegetables taste bitter. Children and adults must learn to like these tastes since at birth, human infants reject bitter and sour tastes. One method parents can use to increase liking for the taste of fruits and vegetables is to make them taste better by mixing these foods with already liked tastes (such as sweeteners) or with nutrients. However, many of the substances that make foods flavorful not only taste good, but they also provide calories. So for the purposes of this article, I will not distinguish between making foods taste good and making them nutritious. Both methods have been shown to independently increase liking in animals and humans.

In one recent study, we noticed that some children (two to five years old) did not like the taste of sour grapefruit juice, as measured in a baseline phase. To increase liking for the sour-tasting juice, we gave children sweetened grapefruit juice over the next twenty days (conditioning phase). After conditioning, children again received the plain (unsweetened) grapefruit juice (testing phase). This test showed that children who initially disliked the juice expressed greater preference for the sour taste compared with baseline measures of liking for grapefruit juice. This increase was persistent weeks later in a follow-up test where children reported still liking the unsweetened, sour-tasting juice.

A similar result was shown using vegetables in adults. Undergraduate students received broccoli and cauliflower mixed with sugar on two occasions. Some college student’s received sweetened broccoli and unsweetened cauliflower; others received sweetened cauliflower and unsweetened broccoli. When later tested with unsweetened broccoli and cauliflower, students rated as more pleasant the vegetable that was given to them earlier as sweetened, as opposed to the vegetable given to them earlier as unsweetened. Similar to the results using grapefruit juice, this study showed that making vegetables more palatable (by sweetening them) decreased dislike for them.

A Short-term Method With Long-Term Results?

Despite the effectiveness of this learning strategy, only about one-third of parents report that they use this method to shift children’s food preferences1. One concern for parents may be with the use of sugars and sweeteners to increase liking. If this is a concern, parents should be aware of two distinct features for this method of learning: First, the sweeteners do not need to contain calories; they simply need to taste sweet. It is likely that non-caloric sweeteners, such as Equal sweetener, would also effectively increase preferences for these fruit juices and vegetables.

Second, preferences are thought to shift permanently without further training. Based on our work, sweetening foods for only a few weeks can cause permanent shifts in liking, even after the sweetener is no longer added. In fact, it has been shown that flavors that were once sweetened continue to be perceived as “tasting” sweet even without being sweetened anymore! This is one potential explanation for why the children in our study continued to like the sour tasting fruit juice weeks later.

At present we can determine that sweetening fruits and vegetables for a short while is an effective strategy to decrease dislike for these foods in children and adults. Also, while further empirical support is needed, a growing literature supports the view that these shifts in liking are long-lasting.

  • Casey, R. & Rozin, P. (1989). Changing children’s food preferences: Parents opinions. Appetite, 12, 171-182.
  • Batsell, W. R., Jr., Brown, A. S., Ansfield, M. E., & Paschall, G. Y. (2002). “You will eat all of that!’”: A retrospective analysis of forced consumption episodes. Appetite, 38, 211-219.
  • Lipsitt, L. P., & Behl, G. (1990). Taste-mediated differences in the sucking behavior of human newborns. In E. D. Capaldi, & T. L. Powley (Eds.), Taste, experience, and feeding (pp. 75–93). Washington, DC: American Psychological Association.
  • Privitera, G. J. (2008). The psychological dieter: It’s not all about the calories. Lanham, MD: University Press of America.
  • Capaldi, E. D. & Privitera, G. J. (2008). Decreasing dislike for sour and bitter in children and adults. Appetite, 50 (1), 139-145.
  • Stevenson, R. J., Boakes, R. A., & Wilson, J. P. (2000). Resistance to extinction of conditioned odour perceptions: Evaluative conditioning is not unique. Journal of Experimental Psychology: Learning, Memory, & Cognition, 26, 423–440.