Biological Properties of Motivation

P A R T T W O

Biological Properties of Motivation

Does the makeup of the human body and mind determine what is motivating? In 1748, the Frenchman La Mettrie published his book Man a Machine, which introduced the idea that the human body is a machine. This machine, however, is different because it has self- awareness/consciousness. Chapter 3 (Evolutionary Antecedents of Motivation) examines how the machine progressed to its current form. The human body evolved because it be- came the best solution for problems of survival. As a result of evolution, humans possess motives and values that are geared toward survival. Motives and values include what we prefer for the beginning and the maintenance of interpersonal relationships, for what we fear, the foods we prefer, even the music we enjoy. These preferences emerge in conscious- ness as likes and dislikes, which motivate behaviors.

Hedonism motivates beneficial behavior, but can it also explain behavior that is detri- mental to a person? Chapter 4 (Addictions and Addictive Behaviors) assumes that pleasure is the reward provided by the natural environment for behaviors that benefit survival. How- ever, we have learned to enhance these pleasures by artificial means with psychoactive drugs like nicotine and alcohol and activities like gambling. Addictive behaviors are exam- ples of natural motivation gone awry. Pleasures designed to reward behaviors necessary for survival are now enjoyed for their own sake to the point of being detrimental to our health.

If the body is a machine, then what motivates a person to keep it in good condition? Chapter 5 (Homeostasis: Temperature, Thirst, Hunger, and Eating) states that sources inside and outside a person provide the motivation for the maintenance of the body. Internally, unpleasant feelings of hot or cold, thirst or hunger motivate behaviors to reduce those feel- ings. Externally, incentives like food, especially sweets and fats, and clothes for tempera- ture control also prompt motivation. The incentive value of food can be so strong, however, that people eat to obesity while others shun it to the point of emaciation (anorexia).

Is behavior always performed as efficiently as possible? Or does efficiency depend on the level of body arousal? Chapter 6 (Behavior, Arousal, and Affective Valence) exam- ines how the body’s degree of arousal determines the efficiency of behavior. Physiological arousal that is too low or too high is associated with poor performance; intermediate arousal is best. Arousal is also associated with the pleasantness of affect. Arousal is most pleasant

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at middle intensities; too little arousal is akin to boredom and too much arousal is distress- ing. Arousal comes from stimulus novelty, incongruity, and complexity as found in humor, music, and suspenseful films.

Finally, can the body as machine have too many demands placed on it? Chapter 7 (Stress, Coping, and Health) shows that if the demands for motivation are too many or too intense, then the machine does not fare well. It breaks down both physically by getting sick and psychologically by worry, anxiety, tension, and unhappiness. Appraisal, social support, and personality traits, however, can intervene between a demand and its potential negative impact. Also, a person can deal directly with the stressor through problem-focused coping or with the stress through emotion-focused coping.

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Evolutionary Antecedents of Motivation

Human nature is the same all over the world, but its operations are so varied by education and habit that one must see it in all its dresses in order to be entirely acquainted with it.

—Lord Chesterfield, 1747

Human action can be modified to some extent, but human nature cannot be changed.

—Abraham Lincoln, 1809–1865

■ In reading this chapter, keep the following questions in mind. They concern universal dispositions, which are characteristic of all people and which play a role in motivating certain behaviors.

1. What is human nature, and how does it relate to motivation and emotion?

2. Are there dispositions or universal motives that apply to all humans?

3. What are the evolutionary and social characteristics for mate preferences, reproductive behavior, and jealousy?

4. What is the contribution of evolution to fear?

5. How did food preferences evolve?

6. Why do people the world over enjoy music?

Evolution of Universal Motives Where in a person’s past is the motivational origin of his or her behavior? By way of anal- ogy, what caused the fall of the last domino pictured in Figure 3.1? Notice that some event must have toppled the first domino, which eventually led to the fall of the last one. Is the cause the domino prior to the last one or the one prior to it and so on back to the initial event? In the case of a person’s current behavior, is the motivation in the recent past like the fall of an immediately preceding domino or in the remote past like the very first domino? Now imagine a man and woman of average height dancing together. First, the man most likely is taller than the woman. This height difference reflects our evolutionary history, which is analogous to the fall of the early dominos. In addition, our imaginary couple is taller today than they would have been a century ago. This increased height is part of our personal history during which more nutritious food became available (Floud et al., 1990)

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FIGURE 3.1 A Metaphor for Evolutionary and Personal History. The toppling of the initial dominoes represents evolutionary history, which topple later dominoes that represent personal his- tory. The 10th or last domino represents motivated behavior in the present.

and is analogous to the fall of later dominos. In other words, the current height of men and women resulted from the interaction between our evolutionary and personal past. Al- though determined in the past, men and women’s current height has an effect on their current behaviors. For example, during conversation women might gaze slightly upward while men gaze downward, women pass more easily through small doorways while men must stoop, and women may need a stool to reach the top shelf that men can reach flat footed. In addition, compared to a century ago, today’s beds are longer, clothes are bigger, and doorways are higher all because of our increased height. Just as these differences in height affect certain behaviors, so too other unspecified characteristics affect behavior. For example, if the couple were ballroom dancing, then the man would lead and the woman would follow.

The purpose of this section is to describe how our evolutionary history and our per- sonal history interact to affect motivation and emotion. There will be an emphasis on the uniformity of certain motives despite the variety of environmental and cultural situations in which people live.

Evolutionary History and Personal History Just as human evolutionary history has shaped the difference in height between men and women, it has also shaped psychological characteristics that determine what does and does not motivate people.

Evolutionary history as a source of motivation focuses on what behaviors humans have in common in spite of vast social and cultural differences. For instance, all humans have brains and faces, but each brain and face is different. All humans are motivated by incentives, but the same incentive does not motivate everyone. All humans laugh and cry, but what triggers these behaviors may differ among humans. Human nature refers to the behavioral, motivational, and emotional similarity among people that results from their common evolutionary history. It is their disposition to behave in a particular fashion,

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C H A P T E R T H R E E / Evolutionary Antecedents of Motivation 51

Environment

a

H er

ed ity

H er

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Environment

b

H er

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Environment

c Environment

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FIGURE 3.2 Relative Contributions of Heredity and Environment. Length and width both contribute to the area of a rectangle, since Area = Length × Width. The relative contribution of length decreases, and width increases from a to d, yet both length and width still contribute to the total area of each rectangle. Similarly, heredity and environment both contribute to the motivation of behavior. The relative contribution of heredity decreases and that of environment increases from a to d, yet both heredity and environment still contribute to the motivation of behavior.

depending on the situation. Human nature is most striking when similarities occur in spite of environmental and cultural differences. It is shaped by natural selection and is geneti- cally transmitted from one generation to the next. It is universal, which means it is the same in societies all over the world. Finally, the behavioral expression of human nature tends to be innate—that is, it is influenced little by experience. The term universal motives will be reserved for the commonality of motives among humans that has evolved over their evolu- tionary history. For example, this term refers to the commonality in what motivates sexual behavior, fear, food preferences, and music enjoyment.

Evolutionary and Personal History Interact. Evolutionary history created human nature, which in turn interacts with our personal history much like the fall of later domi- noes depend on the fall of earlier ones (Figure 3.1). The interaction between evolution- ary history and personal history is another way of stating that the interaction between heredity (nature) and environment (nurture) motivates behavior. The nature of this inter- action was recognized more than 125 years ago by Sir Francis Galton (1883). He claimed that it was difficult to distinguish between that part of human character that results from education and circumstances and that which results from the human constitution. Today, it is accepted that both heredity and environment interact to determine behavior (Plomin et al., 2001).

The relative contribution of heredity and environment is different for various be- haviors. Some behaviors are genetically disposed to occur and thus require little envi- ronmental experience. Other behaviors are genetically neutral and require much environmental experience to occur. For instance, learning to eat is almost automatic, whereas it takes a lot of practice to master long division. The interaction between hered- ity and environment in motivating behavior is illustrated in Figure 3.2 by a series of rectangles (Plomin et al., 2001). A rectangle’s length and width both contribute to its area, since Area = Length × Width, although the relative contribution of each may vary. Simi- larly, heredity and environment both contribute to behavior, but their relative contributions may also vary. Changes in the contribution of heredity and environment are illustrated by

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rectangles a through d in Figure 3.2: the contribution of length (heredity) decreases, and the contribution of width (environment) increases. Although the change from rectangle a to rectangle d represents a decrease in heredity and an increase in environment, both heredity and environment contribute to behavior. Behaviors that are strongly influenced by heredity (rectangle a) are known as innate, which means not taught or not benefitting from experience.

It is important to remember, however, that heredity can influence behavior in more than one way. First, inherited physical features affect a person’s behavior, such as the rela- tionship between the thumb and fingers. How difficult would it be to write, tie a ribbon, or grasp a ball without the use of either a thumb or fingers? Or consider how size and strength differences between men and women contribute to a general division of labor. Men, on average, are bigger and physically stronger and so tend to do heavy work, such as farming, mining, and construction. Women, on average, are smaller and have less muscle mass and so tend to do lighter work, such as cooking and clerical tasks. Second, the hereditary nature, or innateness, of certain feelings or motives disposes humans to react in one way rather than another to various stimuli. The influence of these seemingly innate feelings becomes ap- parent in the prevalence of sexual behavior, certain fears, a baby’s taste preferences, and the universal pleasure of music.

Experience and Motives. As the rectangles in Figure 3.2 illustrate, even behaviors that appear to be totally innate may actually require at least some minimal environmental ex- perience in order to occur (rectangle a). Other behaviors require the benefit of additional experiences (rectangles b through d). To illustrate, we might think of walking as being in- nate, but some prior experience in sitting upright and crawling appears necessary for walking to occur in a timely manner (Dennis, 1960). Other examples of behaviors that occur with little experience are an infant’s crying to indicate hunger or distress. This behavior is fairly complete immediately following birth. As new parents quickly learn, their baby requires little if any practice at this activity. Facial reactions to taste stimuli also seem to be in place in the first few hours of an infant’s life. Little practice, if any, is needed to indicate whether something is tasty or awful (Menella & Beauchamp, 1998; Steiner, 1977).

Finally, an individual’s innate disposition and personal experience usually operate in tandem, which happens for example in the development of gender roles. Thus, infants iden- tified as girls and boys are nurtured along feminine and masculine roles, respectively.

Evolutionary Psychology Human minds are not blank slates at birth upon which experience begins to write. Neither are minds passive recipients of experience. Instead, human minds have been shaped by evolution to adapt to their environment. Our evolutionary past interacts with people’s experiences to determine current motivation. This interaction is the view of evolutionary psychology, which analyzes universal motives in the context of evolution. According to evolutionary psychol- ogy, psychological mechanisms have evolved through natural selection to solve specific problems of adaptation to the environment (Buss, 1995, 1999, 2005). Several of these psy- chological mechanisms are represented by universal motives. Fear of snakes, for instance, evolved to motivate behavior to escape or avoid such dangerous creatures. Food preferences

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TABLE 3.1 Categories of Universal Motives

Universal Motive/Incentive Characteristics

Aesthetics: art, hygiene, music, standards of beauty

Control environment: fire, mood altering substances, shelter, tools

Emotions: anger, contempt, disgust, fear, happy, sad, surprise

Facial expressions: for emotions, for communication, and are modifiable

Fears: loud noises, snakes, strangers in childhood

Goal setting: predict and plan for the future

Self-concept: self as subject, object, and different from other person

Sexual interactions: attraction, sexual jealousy, and regulation

Social milieu: live in social units, rights, obligations of membership, and status

Source: Based on Human Universals by D. E. Brown, 1991, Chapter 6.

for sugar and fat evolved to ensure a person liked food that provided sufficient calories. Women evolved a preference for mates who had the economic resources to provide for them and their children. Male attraction to beauty and desire for sexual variety evolved to ensure the selection of fertile mates and to motivate the seeking of more sexual partners. The func- tion of male sexual jealousy developed to increase a man’s confidence regarding the pater- nity of his children. Each human motive can be considered an instance of a psychological mechanism that evolved because it aided humans in adapting to their environment.

➣ To learn more about evolutionary psychology go to http://www.psych.ucsb.edu/research/cep/

Universal Motives. For a motive to be considered universal it must occur in all countries and cultures of the world even though it might be expressed differently. Different geographical regions, climates, societies, cultures, and customs exist around the world. These differences produce differences in the foods people eat, in social customs, and in educational practices. In spite of these geographical, climatic, and societal differences, uni- versal motivation and behavior are presumably the same for food, custom, and learning. The existence of universal needs or motives was noted by the anthropologist Bronislaw Malinowski (1941), who derived a list of basic needs that he believed existed in societies all around the world. The existence of these needs pushed cultures into ways of satisfying them, although the manner by which this was accomplished varied from culture to culture. Thus, the need for food was satisfied by hunting, gathering, and today a sophisticated system of farm- ing, ranching, and the commerce of bringing food to market. Other bodily needs such as sex, physical comfort, and safety resulted in marriage, shelter, health practices, and systems of laws and justice.

Brown (1991) uses the term universals to describe traits that are found in almost all cultures and societies the world over. Some items in his list can be categorized together for their relevance to universal motives and universally valued incentives (see Table 3.1). Emotional behaviors seem to predominate the list as reflected by the presence of fears, emo- tions, and their accompanying facial expressions. The social nature of human motives is

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exhibited in categories of sexual interactions and the social milieu. Universals with external characteristics express themselves in terms of controlling the environment and setting goals, which contribute to the prevention and alleviation of stress. Universals that seem more removed from human biology are beliefs about aesthetics and concepts about the self. The universal motive categories in Table 3.1 are taken for granted. We forget that entire institu- tions and customs have developed in order to satisfy these motives or attain these valued incentives in today’s societies.

Inherited Structures for Behavior, Motives, and Emotions. How can universal motives, such as fear or food preferences, evolve and pass on to succeeding generations? They do so by way of natural selection (see Chapter 2), which operates at the level of the individual. In turn, an individual’s genes transmit universal motives to the next generation (Mayr, 2001). Genes are those parts of a person’s DNA content that provide the informa- tion necessary for the construction of proteins, which form the building blocks of the var- ious neurophysiological structures that make up the brain and nervous system. Humans receive one-half of their genes from each parent at conception. At this time the sperm con- taining the male’s genetic information unites with the ovum (egg), which contains the female’s genetic information. The resulting combination contains information from each parent, which in turn came from their parents, and so on. Our genes or our genetic past do not influence motivation or behavior directly. Genes provide the information for the build- ing of proteins that are used to create “the skeletal system, muscles, the endocrine system, the immune system, the digestive system, and most important for behavior, the nervous system” (Plomin et al., 2001, p. 47). To say that genes or heredity influence behavior is re- ally a shorthand way of stating that genes are the recipes for various proteins, which in turn produce neurophysiological systems that determine the particular reaction to environmen- tal stimulation (Plomin et al., 2001). Thus, the seeming genetic inheritance of motives or psychological mechanisms simply means that the brain or body appears sensitive to the stimuli evoking or satisfying those motives. For example, different neurons in the tongue and brain react to sweet and bitter stimuli such that infants prefer sweet taste. Genes carry the information for how the tongue’s neurons and the brain’s structure are constructed. At a more global level, however, it appears that variation and selection occur at the level of behavior. After all, behavioral and environmental events are visible, while genes are not; only their end results are visible.

Section Recap The motivation for current behavior has its roots in our evolutionary and personal history. Evolutionary history refers to a person’s genetic makeup or nature, and personal history is the person’s experiences or nurture. Both nature and nurture contribute to what motivates behavior just as length and width both contribute to the area of a rectangle. Usually ten- dencies that are part of human nature operate in tandem with personal experiences as in the development of gender roles. Evolutionary history created human nature, which encom- passes all the behavioral, motivational, and emotional characteristics that all people have in common despite different environmental and cultural differences. Evolutionary psy- chology supposes that part of human nature consists of psychological mechanisms, which have evolved to solve problems of adaptation to the environment. Universal motives are psychological mechanisms that refer to similarities in what motivates people, such as a set

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of basic needs, valued incentives, and social interactions. Societies developed in order to satisfy universals, which are traits found the world over such as fears, emotions, facial ex- pressions, environmental control, goal setting, and beliefs about aesthetics and the self.

Genes are DNA segments that provide information from each parent on how to build the child’s neurophysiological structures. These structures, in turn, are the physical basis for psychological mechanisms or universal motives that, according to evolutionary psychology, evolved to meet environmental problems that humans faced in their evolutionary past.

Universal Motives of Sex, Fear, Food, and Music Much like early dominoes caused the fall of the final domino, natural selection operating in the evolutionary past caused the development of psychological mechanisms and univer- sal motives. These universal motives in turn are satisfied in the current environment. This section examines four major categories of evolved universal motives. One is the motive for sexual behavior in the context of short- and long-term relationships. A second is the mo- tive to prefer certain basic foods and reject others. A third motive concerns the survival value of fear and the stimuli that humans avoid as a consequence. Finally, there is the puz- zle of music. Why do people the world over enjoy music? These motives from our evolu- tionary past push individuals to seek satisfaction, which is achieved in their environment.

Selecting a Mate “They stroke, kiss, nip, nuzzle, pat, tap, lick, tug, or playfully chase this chosen one. Some sing. Some whinny. Some squeak, croak, or bark. Some dance. Some strut. Some preen. Some chase. Most play” (Fisher, 2004, p. 27). In her book Why We Love, Fisher gives many behavioral examples of various animals engaging in behaviors that we can anthropomor- phize as romantic love. In addition to this love play, animals, like humans, exhibit a choosi- ness and do not mate indiscriminately with members of the other sex. A further similarity is that animals, like humans, appear possessive and guard their mates closely as if they are motivated by jealousy. This section examines what factors determine mate choice in humans and how jealousy affects human relationships.

The point of natural selection is to ensure survival and longevity. However, living a long time because of natural selection may benefit an individual but may not benefit the species. For a species to receive the benefits of natural selection, adaptive traits must be passed on to succeeding generations. This requires short- and long-term cooperation between men and women. Short-term cooperation is required for sexual intercourse that leads to conception, and long-term cooperation is necessary for care of any infants. Conse- quently, a major area of interest in evolutionary psychology concerns the establishment and maintenance of human relationships. In terms of pull motivation, what characteristics do men and women look for or select in the other sex to establish a relationship and what do they look for or select to maintain that relationship?

Darwin (1859/1936) used the term sexual selection to refer to the “struggle between males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring” (p. 88). The male could be very aggressive and fight off all other males, thereby having a harem of females all to himself. However, if he could not be the most aggressive then maybe he could be the most charming and attract the most females in that manner. In such cases, the female acts as the selecting agent because it is what she likes

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TABLE 3.2 Mate Value Inventory

Describe yourself as accurately as possible on the traits listed below. Use the following scale:

extremely low on this trait = �3 �2 �1 0 �1 �2 �3 � extremely high on this trait

Ambitious ______ Faithful to partner ______ Kind & understanding ______

Attractive face ______ Financially secure ______ Loyal ______

Attractive body ______ Good sense of humor ______ Responsible ______

Desire for children ______ Generous ______ Shares my values ______

Emotionally stable ______ Healthy ______ Shares my interests ______

Enthusiastic about sex ______ Independent ______ Sociable ______

Note: To compute your mate value, sum your scores on all of the items. The total score reflects the amount of a person’s mate value.

Source: Adapted from “Self, Friends, and Lovers: Structural Relations among Beck Depression Inventory Scores and Perceived Mate Values” by B. R. Kirsner et al., 2003, Journal of Affective Disorders, 75, pp. 135, 147.

about the male that determines whether she allows him to mate with her. For example, the number of copulations performed by a peacock correlates positively with the number of eyespots he has on his train of tail feathers. The greater the number of eyespots, the more likely a peahen is to consent to copulation (Petrie et al., 1991).

➣ Pictures of a peacock’s tail feather display to a peahen are at http://www.pbase.com/ lesliej/peafowl

Mate Value. The possession of characteristics that are desired by the other sex defines a person’s mate value. The higher your mate value, the greater your appeal. The Mate Value Inventory in Table 3.2 is one way to measure one’s self-perceived physical attractiveness and psychological characteristics that may be valued by the other sex (Kirsner et al., 2003). No- tice that a person’s mate value consists of physical features, psychological characteristics, and a value system. Physical features are immediately noticeable in a person but fade with time and are ones to which the other person habituates. Psychological characteristics, how- ever, take time to discover and are less likely to fade. Finally, when interests and values are shared, it increases people’s attraction to each other.

Facial attractiveness is one physical indicator of mate value in Table 3.2 that is of great interest to evolutionary psychologists (Rhodes, 2006). What makes a face attractive to the other sex? One feature is that a more attractive face is more symmetrical, which means the right and left half of a face match up. Another feature is that an attractive face also represents the average of many facial configurations that occur in the population. It is a face that has average lip, eye, and nose size, for example. A final feature that contributes to facial attractiveness is sexual dimorphism, which refers to differences in the form or structure between men and women. More attractive male faces show greater masculinity and more attractive female faces show greater femininity (Rhodes, 2006).

If facial and physical attractiveness are determinants of mate value, then one obvious question is whether increases in attractiveness do indeed increase one’s chances of attracting a mate. Rhodes and coresearchers (2005) investigated this question in an Australian sample of men and women. As a measure of success in attracting a mate, the researchers asked the

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individuals to report their number of sexual partners, age of first intercourse, and the length of each relationship. The photos of the participants were rated for attractiveness, sexual di- morphism, averageness, and symmetry by a separate group of people. Do these indicators of physical attractiveness correlate with sexual experience? The results showed that they did. Individuals with higher physical mate values had more relationship experiences. Men with attractive faces and attractive and masculine bodies had more sexual partners and also became sexually active at an earlier age. Women with attractive faces became sexually active at an earlier age and had more relationships that exceeded 12 months. The results provide some evidence that as one’s mate value increases, the likelihood of attracting others also increases.

➣ Research on attractiveness can be found at http://www.beautycheck.de/english

Good Genes Hypothesis. It is probably safe to state that both women and men prefer at- tractive partners. But what is the reason for this preference? One answer is that attractive- ness is a universally valued incentive that arose during our evolutionary past as a result of sexual selection. The member of the other sex selects an attractive individual based on the assumption that attractiveness signals genes for health, fertility, and intelligence according to the good genes hypothesis. A person with an attractive face presumably has genes for high intelligence, health, a good immune system, and for potentially good parenting skills (Rhodes, 2006). Consequently, if a person selects an attractive long-term mate, then they will produce more offspring, who are more intelligent, healthy, and have the benefit of good parents. Their children would have an increased chance of survival. However, evidence that attractiveness signals health, for example, has been difficult to establish partly because modern medicine and grooming practices obscure a person’s attractiveness and hence any relationship with health (Weeden & Sabini, 2005).

An inverse to the good genes hypothesis is that individuals reject those people whose physical appearance suggests the possibility of bad genes—that is, genes that signal poten- tial disease and low intelligence (Zebrowitz & Rhodes, 2004). The emphasis is on rejecting people, not attracting them. Zebrowitz and Rhodes (2004) tested this hypothesis with lon- gitudinal data from individuals for whom facial photos, intelligence test scores, and health indicators were available at ages 10, 11–15, 17, and 30–40 years. The photos were rated for facial quality, such as attractiveness, symmetry, averageness, and sexual dimorphism. The individuals were also judged for intelligence and health on the basis of their photos. In order to examine whether people with unattractive faces are rejected, the researchers divided the photos at the median based on attractiveness. Individuals categorized below the median were judged as less attractive at all ages, had less facial symmetry, and male faces showed less masculinity. The researchers reasoned that if facial attractiveness correlates with health and intelligence, it is likely to be exhibited in faces below the median. In other words, to be selected as a mate one must possess a face with a minimal level of attractiveness, which would indicate some minimal level of health and intelligence. The results showed a positive correlation between facial attractiveness, intelligence, and health, but only for individuals whose faces were below the median. For these faces, as rated attractiveness decreased, judg- ments of the individuals’ health and intelligence decreased correspondingly. This relation- ship was also true when actual indicators of health and intelligence were used: faces with lower attractiveness were associated with poorer health and lower intelligence. Thus,

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according to the bad genes hypothesis, people avoid mating with individuals who have extremely poor physical appearance or low facial attractiveness. In regard to sexual selection, it is not that people are pulled toward a face with high mate value but instead are repelled by one with poor mate value—that is, one that signals poor health and low intelligence.

Universality of Beauty and Health. Facial attractiveness evolved through sexual selec- tion. Consequently, the basis of attractiveness and its relationship to health is assumed to be universal and not culturally specific. This claim is based on research that has resulted in sev- eral convincing conclusions (Langlois et al., 2000). First, people agree on who is beautiful and who is not within their culture. Second, people agree on the standards of beauty for faces in cultures other than their own. Third, people agree on the degree of attractiveness among chil- dren. Presumably, then, the association between an evolved set of features and physical health or intelligence should be similar everywhere. For example, a runny nose and watery eyes that are linked to a cold would be assumed to be unattractive compared to the same face when a person does not have a cold. However, there may be instances of cultural standards of beauty that are not linked to health. For example, thinness in women is associated with beauty and health, although extreme thinness is associated with poor health (Weeden & Sabini, 2005).

Sex Differences in Long-Term Mate Selection. Once mates are selected and relation- ships are formed, then the birth of offspring and parenthood is frequently the next step. Thus, other aspects of mate value besides physical beauty are important for relationships. These aspects are important because evolutionary success is based on leaving the most number of surviving offspring. Furthermore, the biological differences between men and women determine what mate values are important. What are these differences?

First, men and women differ in the time investment they make in their offspring (D. M. Buss, 1989). After sexual intercourse, a woman invests an additional 38 weeks as the baby develops so that at birth the woman already has invested much more time in the child than the man. In addition, since she can produce many fewer children than a man, it is more important that a woman help each child that is born to survive; by doing so, she increases her reproductive success. Since a man is capable of having innumerable children, he may not in- vest as heavily in each individual child as a woman would. He increases his reproductive suc- cess by having intercourse with as many women as possible, thereby conceiving many children. Thus, the strategies a woman employs to ensure the survival of her children and hence the perpetuation of her genes is different than the strategies a man employs for the per- petuation of his genes. Consequently, we would expect a woman to look for characteristics in a man that indicate greater commitment and help in raising children. Men should prefer characteristics related to reproductive value, such as a woman’s physical health and youth. In mating with a fertile woman a man can maximize his reproductive success by having many children with her (D. M. Buss, 1989).

This difference in what men and women value in long-term mates is assumed to have universal appeal and has led evolutionary psychologists to concentrate on three mate-value characteristics: good financial prospect, ambition and industriousness, and good looks (D. M. Buss, 1989). If differences in sexual preferences among men and women are uni- versal, then ratings of these characteristics should differ in societies all over the world. This is exactly what D. M. Buss (1989) attempted to show by surveying men and women in 37 different countries. Figure 3.3 shows the results of six different countries: Japan, India,

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Motivation: Biological, Psychological, and Environmental, Third Edition, by Lambert Deckers. Published by Allyn & Bacon. Copyright © 2010 by Pearson Education, Inc.

 

 

C H A P T E R T H R E E / Evolutionary Antecedents of Motivation 59

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