Did your parents ever tell you to put a little more green on your plate? How about orange? Or maybe you’ve heard the phrase eat the rainbow. It may seem a bit odd to talk about nutrition in terms of colors, but we’d bet that thinking about green and orange probably got you to eat at least a few more brussels sprouts and carrots!
Why is this? From a behavioral point of view, eating the rainbow is an intuitive rule of thumb (or heuristic) that helps us get a balance of key nutrients without meticulously tracking (or even knowing!) the vitamins and minerals in each type of food we consume. It makes otherwise complex nutrition decisions simple, which in turn helps us remember what we should be eating and makes us more likely to follow through with healthy eating choices.
Rules of thumb, like eat the rainbow, are not only powerful for us in our food choices, they are also useful tools for the people producing the food we eat – farmers. In one of our agricultural projects in Kenya, our partners at Juhudi Kilimo taught us about a useful rule of thumb for identifying quality dairy cows. You can spot a high-quality dairy cow by looking for bony shoulders and a large belly. A large belly indicates that the cow has a large stomach with plenty of capacity for making milk. Bony shoulders indicate that the substantial weight of this large belly is causing the skin to pull on the shoulders, making them appear bony. This is a great rule of thumb, because it simplifies complex information about bovine anatomy into an easy-to-apply shortcut, but it is also counterintuitive.
The rule of thumb we learned about in Kenya is effective, but it also seems to go against common reason! In most situations, if you see a bony person or animal, you might think that they aren’t very healthy. Dairy cows prove an exception to this rule. Had we applied a heuristic for health that works for humans or other animals to dairy cows, we may have made a mistake. Rules of thumb can trip us up if they apply in one situation, but not another. We can also be led astray in how we interpret our rules of thumb. Thinking back to our nutrition heuristic, we could very well eat the rainbow by solely consuming multi-colored gummy bears. We would technically be following the guideline, but would definitely not be eating a balanced and nutritious diet.
In another project working with cotton farmers in Mozambique, we encountered a widely used, yet misapplied heuristic that was leading farmers astray with serious consequences. Many farmers told us that they plant their cotton on December 15th every year. From a technical perspective, the best time to plant rain-fed cotton is as soon as the soil has been saturated with water to 30mm deep. In the past, this date-based heuristic aligned with the technical guidelines and was reliable because weather patterns correlated with the time of year. However, in Mozambique, and many other parts of the world, rainfall patterns are increasingly unpredictable, meaning that a date-based rule of thumb has become misleading and often useless. In fact, we observed that many farmers were planting their cotton at a less than optimal time. After identifying this problem and recognizing the faulty heuristic, we helped farmers shift to a rain-based heuristic along the lines of: “I plant my cotton after the first big rainfall” of the season.
Whether we work on a farm in Mozambique or in an office in Manhattan, we all use heuristics. These mental shortcuts are incredibly useful and help us make hundreds of decisions on a daily basis. Useful as they are, heuristics can sometimes lead us astray – keep this in mind as you reflect on the rules of thumb that guide your life!
In light of National Nutrition Month, we want to hear some of your favorite nutrition-related heuristics. Tweet @ideas42 with your own rules of thumb– these can be about nutrition, agriculture, cooking or anything else related to food!