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1 I N T RO D U C T I O N The Essential Nutrients of the Psychology of Eating and Drinking SIR TOBY— Does not our life consist of the four elements [earth, air, fire, and water]? SIR ANDREW— Faith, so they say; but I think it rather consists of eating and drinking. SIR TOBY— Copyright © 2014. Taylo...

1 I N T RO D U C T I O N The Essential Nutrients of the Psychology of Eating and Drinking SIR TOBY— Does not our life consist of the four elements [earth, air, fire, and water]? SIR ANDREW— Faith, so they say; but I think it rather consists of eating and drinking. SIR TOBY— Copyright © 2014. Taylor & Francis Group. All rights reserved. Thou art a scholar; let us therefore eat and drink. William Shakespeare (1623/1936)1 Have you ever noticed just how much of your time is devoted to eating and drinking, or to thinking about eating and drinking? Pick a day and try keeping a record of the total time that you spend preparing or eating meals and snacks, as well as the time that you spend just thinking about the foods and drinks that you will or won’t have. You’ll likely find that far more time is devoted to these activities than to anything else, including sex. I once used a stopwatch to record how much total time I spent thinking about or touching food. My total was 4 hours and 33 minutes, and I’m not any more obsessed with food than is the average person. A great deal of the behavior of all animals consists of obtaining and consuming foods and liquids. It doesn’t take a scientist to know this. Supreme Court Justice Sonia Sotomayor stated in her autobiography: “And always food at the center of it all.”2 But it does take a scientist to find out what causes these foodand drink-related behaviors. And once we understand the causes, then we may be able to change these behaviors, something that a lot of people would like to do for many different reasons. For example, I’m sure that you’ve noticed that a lot of people consume so much of certain foods and drinks that bad things happen—such as 1 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. Copyright © 2014. Taylor & Francis Group. All rights reserved. THE PSYCHOLOGY OF EATING AND DRINKING weight gain from eating too much chocolate, high cholesterol from eating too much of certain kinds of fats, and liver damage from drinking too much alcohol. Why do people do these things? And, even more intriguing, why do some people overconsume these foods and drinks more than other people or only at certain times? Why do women tend to crave chocolate at certain points in the menstrual cycle, for instance? We need to understand the causes of behaviors such as these. Once we do, we’ll have important information to guide us in modifying these behaviors. Our fascination with such eating and drinking behaviors and their causes has resulted in a huge industry of food-related pop science. Every bookstore, every magazine stand, every grocery store checkout counter is filled with publications about how to get your child to eat vegetables, how to tell if someone has an eating disorder, or, most commonly, how to lose weight. TV programs and movies on these subjects abound. But the degree to which any of these is based on scientific research is very limited. Thus the information and advice offered is, at best, incomplete, and is often simply incorrect. Let’s take as an example the advice that to eat less you should drink lots of water. Have you ever heard that? Well, it’s completely untrue; people don’t eat less when they drink more water. And after you read this book, you’ll understand why. This book is different from what you’ll find in most magazines or books. It will introduce you to the scientific study of eating and drinking behavior. It will show you how scientists, particularly psychologists, conduct research on eating and drinking and what they have been able to find out so far. It will tell you many of the latest discoveries in this field. The answers aren’t always simple, and they aren’t always what we’d like to hear. But if you want accurate information about what causes our eating and drinking behavior, and about what we can and can’t do to change that behavior, you’ll get that information here. And while you may not always be able to use that information to change your own behavior or someone else’s—serious eating and drinking problems require professional help—you will get much immediately useful information. What’s Psychology Got to Do With Eating and Drinking? Most of the information in this book is drawn from carefully conducted psychology experiments. Psychology is the science of behavior, the science of “how and why organisms do what they do.”3 So if your goal is to understand the behavior of people and other animals, as opposed to, say, the reproduction of plant cells, then psychology is your field. In this book we’ll look at a certain set of behaviors—the behaviors involved in eating and drinking—using many different types of psychological 2 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. Copyright © 2014. Taylor & Francis Group. All rights reserved. CHAPTER 1: INTRODUCTION approaches, from the physiological to the social. Our strategy will be to use whatever psychological science can tell us about these behaviors. We have something we want to understand—eating and drinking behaviors—and we’re going to use every possible tool to gain that understanding. Psychology is the science of behavior, and therefore the analytical method that you’ll see used throughout the entire book is the scientific method. The scientific method assumes that the laws of nature govern all things and that they do so in a consistent manner for all people and other animals at all times. Without this scientific orientation it would be impossible to conduct experiments to determine the causes of behavior. In an experiment, all conditions are held constant except for one aspect that is manipulated by the experimenter. If this change in one factor is followed by a change in the behavior of the subject, the experimenter concludes that manipulating that factor has the observed effect on behavior. For example, you might take 10 people, ensure that they had eaten and drunk the exact same things for the 6 hours prior to dinner, have half of them drink a quart of water right before dinner, and then measure how much they all ate during dinner. If, on average, the people who drank the extra water ate less than the other people, you could conclude that drinking lots of water decreases how much people eat right after drinking the water. Of course, this experiment wouldn’t tell you what might happen at breakfast the next morning; the water drinkers might make up for their smaller dinners by eating larger breakfasts. You would need to do another experiment, or expand your original experiment, to determine that. All psychological scientists assume a scientific orientation in their work. The study of the psychology of eating and drinking is a huge but fascinating subject. It includes research on how you detect tastes, why you become hungry or thirsty, why you like some foods more than others, how you choose among foods, how certain foods can affect your behavior, and how and why we sometimes eat and drink in less than ideal ways. It would be impossible to cover all of the psychology of eating and drinking in one book. But I hope that this book will give you a good overview or, more appropriately, a good taste of this subject. Getting There by Degrees: Evolution and Eating and Drinking In doing any kind of scientific investigation, it helps if you have some conceptual framework that guides where you’re going, some theory or theories that suggest how things work, so that you’ll have specific ideas to test and ways to describe your findings as a whole. Psychological 3 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. Copyright © 2014. Taylor & Francis Group. All rights reserved. THE PSYCHOLOGY OF EATING AND DRINKING science, particularly psychological science as it’s applied to eating and drinking behaviors, is often organized around the concepts of evolution and natural selection. The reason that the concepts of evolution and natural selection seem particularly appropriate for the psychology of eating and drinking is that every animal, including every person, must eat and drink appropriately or it will die. This means that any animal that has some genetically influenced behavior or anatomical trait that enables it to eat and drink well will be more likely to survive and will have more offspring than will other members of that species. Therefore you would expect the eating and drinking behaviors of all species to have evolved over the millennia so as to be beneficial; you would expect that, by the process of natural selection, individuals who are well adapted with regard to how they eat and drink have survived and reproduced. Repeatedly in this book you’ll hear me say that some way in which a species eats or drinks is adaptive and has helped that species to survive. At this point I hope that you’re saying, “Wait a minute. You’re telling me that people and other animals have evolved to eat and drink well. But we all know, and you wrote yourself earlier in this chapter, that people eat and drink in all kinds of harmful ways. If we have evolved to eat well, why is it, for example, that people eat so much chocolate that they gain weight?” Just because natural selection is and has been in operation doesn’t mean that all of the behaviors of every species will be perfectly adapted for every situation. In fact, there are several reasons why an animal’s eating behavior might not be optimal. Just one such reason is that you may be observing the animal in a situation different from the one to which its species was adapted. We didn’t evolve in surroundings where chocolate was easily and cheaply available around every corner, and with our advanced medical techniques, people usually don’t die at young ages from overeating chocolate. Therefore, despite the harmful effects of overeating chocolate, those of us who are chocolate-obsessed are still having lots of children. In this book you’ll read many explanations such as this of unhealthy eating and drinking behaviors. Getting Down to the Subject Now that we have our theoretical framework for experiments on the psychology of eating and drinking, let’s suppose that you’re a scientist thinking about an experiment that you might do to find out why people like chocolate so much. Let’s assume that you’ve read research suggesting that a particular gene results in people loving chocolate after they’ve had many years of exposure to it, and you want to find out for sure if that’s true. Therefore you design an experiment in which you’ll take 50 4 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. Copyright © 2014. Taylor & Francis Group. All rights reserved. CHAPTER 1: INTRODUCTION people with identical genes, give half of them chocolate from birth to age 25 while preventing the others from having any contact with chocolate during those years, and then test all of the participants’ preferences for chocolate when they are and aren’t hungry. Sound like a great experiment? Well it is, but there are a few practical problems. To begin with, you’ll never find 50 people with identical genes. Even finding two (identical twins) is hard. Second, what scientist is going to have the patience to do an experiment that lasts 25 years? Scientists are under great pressure to publish frequently in order to keep getting research grants and to get promoted at their universities. Third, where are you going to get enough money to do this experiment? The participants will expect to get paid for their time, which will be considerable. And 25 years of chocolate for 25 people will also cost quite a lot. Fourth, you might have to deprive the participants of food for a period of time in order to make sure that they’re hungry. Is this ethical? Issues such as these have resulted in scientists often using animals other than people in their experiments, something that you’re going to read a lot about in this book. This should give you some concern; after all, only people behave just like people. However, in addition to the practical considerations, when you’re trying to understand people’s eating and drinking behaviors, there are good reasons for using animals other than people in the experiments. If I’ve convinced you that evolution has shaped eating and drinking behaviors, then you must also accept that different species will have at least some similar eating and drinking behaviors. One reason for this is that some species have evolved from relatively recent common origins. For example, all mammals have ancestors in common and, therefore, have some genes in common. Thus the process of evolution ensures that, even if your primary interest is the eating and drinking behaviors of people, you can learn something of value from studying the eating and drinking behaviors of other species. Let’s consider some of the advantages and disadvantages of using different species in our hypothetical chocolate experiment. As you read this material, you should be able to see many similarities in the eating and drinking behaviors of different species, while at the same time noting significant differences in the ways that these different species interact with their particular surroundings. Let’s start with the sea slug Pleurobranchaea. This slug is a carnivore—a meat eater. It’s not much to look at; the beauty of this animal is definitely more than skin deep. Pleurobranchaea, similar to people, has specialized cells (known as neurons) in its body that collect information about its surroundings and cause it to move. Together these cells are known as a neuronal system. Pleurobranchaea’s neuronal system is less complex than ours. Therefore its neurons are relatively easily identified and manipulated. 5 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. Copyright © 2014. Taylor & Francis Group. All rights reserved. THE PSYCHOLOGY OF EATING AND DRINKING Some of Pleurobranchaea’s neurons, called food command neurons, are responsible for making Pleurobranchaea move automatically in order to eat food that it has detected. This is an example of a reflex, a specific response that occurs reliably following exposure to specific aspects of the surroundings. In such a case no learning is involved. Scientists have been able to determine that what Pleurobranchaea has recently eaten affects this reflex—Pleurobranchaea’s motivation—by influencing how much certain inhibitory neurons decrease the activity of the food command neurons. Whether or not this slug eats can also be affected by learning— Pleurobranchaea’s knowledge about which events occur together. For example, if an experimenter shocks Pleurobranchaea whenever it eats, it will be less likely to approach and consume food.4 Exciting as it is to be able to see the precise changes in neuronal activity that represent changes in feeding behavior, the usefulness of Pleurobranchaea as a model of our feeding behavior is limited due to this species’ limited behavioral repertoire. To begin with, due to its carnivorous proclivities, Pleurobranchaea would be useless in an experiment on chocolate. Let’s consider using a mammal for our experiment. People are mammals—animals that suckle.5 Therefore, other mammalian species would seem the most likely choices for studies on the eating and drinking behaviors of people. In the early days of physiological investigations of hunger, one mammalian species—dogs—was a frequent choice for experimental subjects. Dogs, although technically considered carnivores, can consume a wide variety of foods,6 making their eating behaviors more similar to ours than is the case for Pleurobranchaea. Dogs will, on occasion, eat chocolate. In addition, their social behaviors and ability to learn quickly can make them useful in studying a number of eating behaviors that are similar to behaviors seen in people. Some of the earliest and best known feeding research with dogs was conducted by one of the most famous parents of psychology, Ivan Pavlov, beginning around 1900.7 Pavlov showed that if an attendant repeatedly gave a dog food, the dog would come to salivate simply on hearing the attendant approaching. If you have a cat, you have certainly seen something similar. (See Figure 1.1.) My pet cat, like everyone else’s, went crazy when he heard any can being opened. Pavlov’s research became the foundation of one of the two major branches of learning theory, the branch concerned with learned and unlearned reflexes that is known as classical conditioning. Nevertheless, despite the fact that dogs sometimes eat chocolate, they are rarely used in current research because they are relatively large in size, take a relatively long time to reach maturity, and are popular pets. Chimpanzees, another mammalian species, are close evolutionary relatives of people. Therefore, not surprisingly, many of their eating and drinking behaviors are similar to those of people. (See Conversation Making Fact #1.) For example, just like people, they’re omnivores; they 6 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. CHAPTER 1: INTRODUCTION “Zelda! Cool it!... The Rothenbergs hear the can opener!” Copyright © 2014. Taylor & Francis Group. All rights reserved. Figure 1.1 D  rawing by Gary Larson. Copyright 1989 FarWorks, Inc. (Reprinted with permission from Gary Larson, Wildlife Preserves: A Far Side Collection, Kansas City: Andrews and McMeel, 1989, p. 92.) can eat fruit, insects, and meat. In addition, similar to people, chimpanzees use spatial memory to find and remember good food sources.8 Some of the most fascinating information about the eating and drinking behaviors of chimps has come from the pioneering investigations of primatologist Jane Goodall and her colleagues at the Gombe National Park in Tanzania, East Africa. Goodall was the first to discover that chimps make tools for obtaining food and water: twigs, stripped of leaves, to which termites cling when the twigs are stuck into their nests, and chewed-up leaves that can be used as sponges to obtain water from tree hollows (see Figure 1.2). Never before had a species other than ours been seen to construct tools.9 Goodall was also the first to discover that chimpanzees hunt other animals and consume their meat. Usually males engage in these hunts and they demonstrate elements of cooperative hunting behavior. One chimp creeps toward the prey while other chimps position themselves to block the prey’s escape routes. After the hunters 7 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. THE PSYCHOLOGY OF EATING AND DRINKING Conversation making fact #1 Copyright © 2014. Taylor & Francis Group. All rights reserved. Do you sprinkle salt on your french fries or on your eggs? Some monkeys also “season” their food. Travel to a small island called Kashima in Japan, and you might see a group of monkeys seasoning their sweet potatoes in saltwater using a method that Japanese scientists saw develop about 60 years ago.10 In 1952, the scientists began giving the monkeys sweet potatoes to eat. The sweet potatoes were frequently covered with sand. In 1953, a female monkey named Imo began to wash the sweet potatoes. Imo would dip a sweet potato into the water with one hand and then brush off the sand with her other hand. By 1958, approximately 80 percent of the monkeys were washing sweet potatoes. During the period that most of the monkeys began to do this, the way that they washed the potatoes began to change. At first the sweet potatoes had been dipped only in fresh water. By 1961, the potatoes were being dipped primarily in salt water. Further, the monkeys would take a bit of a sweet potato, dip it, and then take another bite, “seasoning” the sweet potato—much yummier than plain sweet potato, and just like what we often do with our food. Figure 1.2 Chimpanzee obtaining termites from a termite nest. 8 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. Copyright © 2014. Taylor & Francis Group. All rights reserved. CHAPTER 1: INTRODUCTION catch and kill the prey, they often share the food among themselves, as well as with other chimps.11 The similarities between our and chimpanzees’ eating and drinking behaviors are indeed remarkable. Yet it’s precisely this close similarity that makes many people consider chimps an inappropriate choice for experiments. Because chimps are so similar to people, ethical constraints that would apply to using people in experiments might also apply to using chimps. There are also several practical disadvantages to using chimps in experiments. Just as with people, chimps are very expensive to maintain, can be difficult to handle, and take a long time to produce sexually mature offspring. For all of these reasons, psychologists have usually not worked with chimps—or other primates—in the investigation of eating and drinking behaviors. This brings us, finally, to the rat (surprise!). Perhaps the rat isn’t your favorite animal, but without question it’s the favorite subject for experiments on the psychology of eating and drinking. There are many reasons for this. The rat’s diet is diverse and very similar to that of people, which accounts for its ability to flourish for so many centuries in close association with us. Rats, for example, absolutely love chocolate. In addition, except that they can’t vomit, the individual and social behaviors that rats use in avoiding poisons and identifying beneficial foods are in many ways similar to those of people. Further, laboratory rats, bred for docility, are easy to handle.12 They’re also relatively inexpensive to buy and maintain, and they reach sexual maturity only about 2 months after birth.13 Finally, the extensive amount of information that scientists have already collected concerning rats provides a rich framework into which to place the results of any new investigations.14 The scientific literature lists these reasons for why the rat has become the favorite experimental subject. However, I’ve always wondered whether there might be other contributing factors. Having spent many years with laboratory rats, I can attest to the fact that they can be quite cuddly, even affectionate, similar to hamsters or guinea pigs. At least for me, it’s a lot harder to imagine snuggling up to a slug or a chimp than to a rat. Conclusion In addition to justifying the liberal use of rat research in the rest of this book, I hope that this chapter has given you a sense of the rich variety and also enormous similarities among different species’ eating and drinking behaviors. Similar principles govern the behaviors of many species. Yet each species has adapted to a different part of the world, a particular ecological niche. Each species obtains food and drink from its surroundings in its own particular way.15 Therefore each species has much to tell us 9 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04. THE PSYCHOLOGY OF EATING AND DRINKING Copyright © 2014. Taylor & Francis Group. All rights reserved. about the nature and origins of eating and drinking behaviors. For many reasons, rats are usually the best choice for studies in which the goal is to apply the results to people. Nevertheless, other species have provided and will provide us with much sustenance in our quest to understand the psychology of eating and drinking. 10 Logue, Alexandra W.. The Psychology of Eating and Drinking, Taylor & Francis Group, 2014. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=1873771. Created from mqu on 2023-11-06 09:33:04.