Infancy is the stage of development that begins at birth and lasts between 18 and 24 months. Although infants seem to be capable of little more than squalling and squirming, research shows that they are much more sophisticated than they appear.

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New parents like to stand around the crib and make goofy faces at the baby because they think the baby will be amused. What they don’t know is that newborns have a rather limited range of vision. The level of detail that a newborn can see at a distance of 20 feet is roughly equivalent to the level of detail that an adult can see at 600 feet (Banks & Salapatek, 1983), which is to say that they are missing out on a lot of the cribside shenanigans. On the other hand, when stimuli are 8 to 12 inches away (about the distance between a nursing infant’s eyes and its mother’s face), newborns can see pretty well. How do we know? In one study, newborns were shown a circle with diagonal stripes over and over again. The infants stared a lot at first and then less and less on each subsequent presentation. Recall from the Learning chapter that habituation is the tendency for organisms to respond less intensely to a stimulus the more frequently they are exposed to it, and infants habituate just like the rest of us do. But when the researchers rotated the circle 90°, the newborns once again stared intently, indicating that they had noticed the change in the circle’s orientation (Slater, Morison, & Somers, 1988).

Newborns are especially attentive to social stimuli. For example, in one study, researchers stood close to some newborns while sticking out their tongues and stood close to other newborns while pursing their lips. Newborns in the first group stuck out their own tongues more often than those in the second group did, and newborns in the second group pursed their lips more often than those in the first group did (Meltzoff & Moore, 1977). Indeed, newborns have been shown to mimic facial expressions in their very first hour of life (Reissland, 1988) and to mimic speech sounds as early as 12 weeks (Kuhl & Meltzoff, 1996).

Although infants can use their eyes right away, they must spend considerably more time learning how to use their other parts. Motor development is the emergence of the ability to execute physical actions such as reaching, grasping, crawling, and walking. Motor behavior starts with a small set of reflexes, which are specific patterns of motor response that are triggered by specific patterns of sensory stimulation. For example, the rooting reflex is the tendency for infants to move their mouths toward any object that touches their cheek, and the sucking reflex is the tendency to suck any object that enters their mouths. These two reflexes allow newborns to find their mother’s nipple and begin feeding—a behavior so vitally important that nature took no chances and hardwired it into every one of us. Interestingly, these and other reflexes that are present at birth seem to disappear in the first few months.

The development of more sophisticated motor behavior tends to obey two general rules. The first is the cephalocaudal rule (or the “top-to-bottom” rule), which describes the tendency for motor behavior to emerge in sequence from the head to the feet. Infants tend to gain control over their heads first, their arms and trunks next, and their legs last. A young infant who is placed on her stomach may lift her head and her chest by using her arms for support, but she typically has little control over her legs. The second rule is the proximodistal rule (or the “inside-to-outside” rule), which describes the tendency for motor behavior to emerge in sequence from the center to the periphery. Infants learn to control their trunks before their elbows and knees, which they learn to control before their hands and feet (see FIGURE 10.2). Motor behaviors generally emerge in an orderly sequence but not on a strict timetable. Rather, the timing of these behaviors is influenced by many factors, such as the infant’s incentive for reaching, body weight, muscular development, and general level of activity. In one study, infants who had visually stimulating mobiles hanging above their cribs began reaching for objects 6 weeks earlier than infants who did not (White & Held, 1966).

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In the first half of the 20th century, a Swiss biologist named Jean Piaget noticed that when asked certain kinds of questions (e.g., “Does the big glass have more liquid in it than the small glass? Can Billy see what you see?”), children of the same age gave the same wrong answers. And as they aged, they started giving the right answers at about the same time. This led Piaget to suggest that children move through discrete stages of cognitive development, which is the emergence of the ability to think and understand. Between infancy and adulthood, children must come to understand three important things: (a) how the world works, (b) how their minds represent that world, and (c) how other minds represent that world. Let’s see how children accomplish these three essential tasks.

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Discovering the World

Piaget (1954) suggested that cognitive development occurs in four stages which he called the sensorimotor stage, the preoperational stage, the concrete operational stage, and the formal operational stage (see TABLE 10.1). The sensorimotor stage is a period of development that begins at birth and lasts through infancy. As its name suggests, infants at this stage are mainly busy using their ability to sense and their ability to move to acquire information about the world. By actively exploring their environments with their eyes, mouths, and fingers, infants begin to construct schemas, which are theories about of the way the world works.

As every scientist knows, the key advantage of having a theory is that it can be used to predict what will happen in novel situations. If an infant learns that tugging at a stuffed animal causes the toy to come closer, then that observation is incorporated into the infant’s theory about how physical objects behave when pulled, and the infant can later use that theory when he or she wants a different object to come closer, such as a rattle or a ball. Piaget called this assimilation, which is the process by which infants apply their schemas in novel situations. Of course, if the infant tugs the tail of the family cat, the cat is likely to sprint in the opposite direction. Because an infants’ theories about the world (“Things come closer if I pull them”) are occasionally disconfirmed, infants must occasionally adjust their schemas in light of new experiences (“Aha! Only inanimate things come closer when I pull them”). Piaget called this accommodation, which is the process by which infants revise their schemas to take new information into account.

Piaget suggested that infants lack some very basic understandings about the physical world and therefore must acquire them through experience. For example, when you put your shoes in the closet, you know that they exist even after you close the closet door, and you would be rather surprised if you opened the door a moment later and found the closet empty. But according to Piaget, this wouldn’t surprise an infant because infants do not have a theory of object permanence, which is the belief that objects exist even when they are not visible. But modern research suggests that infants may acquire a sense of object permanence much earlier than Piaget realized (Shinskey & Munakata, 2005).

For instance, in one study, infants were shown a miniature drawbridge that flipped up and down (see FIGURE 10.3). Once the infants got used to this, they watched as a box was placed behind the drawbridge—in its path but out of their sight. Some infants then saw a possible event: The drawbridge began to flip and then suddenly stopped, as if impeded by the box that the infants could not see. Other infants saw an impossible event: The drawbridge began to flip and then continued, as if unimpeded by the box. Four-month-old infants stared longer at the impossible event than at the possible event, suggesting that they were puzzled by it (Baillargeon, Spelke, & Wasserman, 1985). The only thing that could have made it puzzling, of course, was the fact that the unseen box was not stopping the progress of the drawbridge (Fantz, 1964). Studies such as these suggest that infants may indeed have some understanding of object permanence by the time they are just 4 months old.

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Discovering the Mind

The long period following infancy is called childhood, which is the stage of development that begins at about 18 to 24 months and lasts until about 11 to 14 years. According to Piaget, children enter childhood at the preoperational stage, which is the stage of cognitive development that begins at about 2 years and ends at about 6 years, during which children develop a preliminary understanding of the physical world. They then pass through the concrete operational stage, which is the stage of cognitive development that begins at about 6 years and ends at about 11 years, during which children learn how actions or “operations” can transform the “concrete” objects of the physical world.

The difference between these stages is nicely illustrated by one of Piaget’s clever experiments in which he showed children a row of cups and asked them to place an egg in each. Preoperational children were able to do this, and afterward they readily agreed that there were just as many eggs as there were cups. Then Piaget removed the eggs and spread them out in a long line that extended beyond the row of cups. Preoperational children incorrectly claimed that there were now more eggs than cups, pointing out that the row of eggs was longer than the row of cups and hence there must be more of them. Concrete operational children, on the other hand, correctly reported that the number of eggs did not change when they were spread out in a longer line. They understood that quantity is a property of a set of concrete objects that does not change when an operation such as spreading out alters the set’s appearance (Piaget, 1954). Piaget called the child’s insight conservation, which is the notion that basic properties of an object do not change despite changes in the object’s appearance.

The main reason why preoperational children do not fully grasp the notion of conservation is that they do not fully grasp the fact that they have minds and that these minds contain mental representations of the world. As adults, we naturally distinguish between appearances and realities. We realize that things aren’t always as they seem: A wagon can be red but look gray at dusk, and a highway can be dry but look wet in the heat. Visual illusions delight us precisely because we know that things look like this but are really like that. Preoperational children don’t make this distinction. When something looks gray or wet, they assume it is gray or wet.

But as children move from the preoperational to the concrete operational stage, they begin to realize that the way the world appears is not necessarily the way the world really is. For instance, concrete operational children can understand that when a ball of clay is rolled, stretched, or flattened, it is still the same amount of clay despite the fact that it looks larger in one form than in another. They can understand that when water is poured from a short, wide beaker into a tall, thin cylinder, it is still the same amount of water despite the fact that the water level in the cylinder is higher. Once children can make a distinction between objects and their mental representations of those objects, they begin to understand that certain operations—such as squishing, pouring, and spreading out—can change what an object looks like without changing what the object is like.

Once children are at the concrete operational stage, they can readily solve physical problems involving egg-spreading and clay squishing. They learn to solve nonphysical problems with equal ease at the formal operational stage, which is the final stage of cognitive development that begins around the age of 11, during which children learn to reason about abstract concepts. Childhood ends when formal operations begin, and people are able to reason systematically about abstract concepts such as liberty and love, about events that have not yet happened, and about events that might have happened but didn’t. The ability to generate, consider, reason about, or mentally “operate on” these abstract concepts, is the hallmark of formal operations.

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Discovering Other Minds

As children develop, they discover their own minds, but they also discover the minds of others. Because preoperational children don’t fully grasp the fact that they have minds that mentally represent objects, they also don’t fully grasp the fact that other people have minds that often represent the same objects in different ways. As such, preoperational children generally expect others to see the world as they do. Egocentrism is the failure to understand that the world appears different to different people. Egocentrism is a hallmark of the preoperational stage, and it reveals itself in a variety of interesting ways. When 3-year-old children are asked what a person on the opposite side of a table is seeing, they typically claim that the other person sees what they see. They also think that others know what they know. For example, in a standard version of the false-belief task (Wimmer & Perner, 1983), children see a puppet named Maxi deposit some chocolate in a cupboard and then leave the room. A second puppet arrives a moment later, finds the chocolate, and moves it to a different cupboard. The children are then asked where Maxi will look for the chocolate when he returns: in the first cupboard where he initially put it, or in the second cupboard where the children know it currently is? Most 5-year-olds realize that Maxi will search the first cupboard because Maxi did not see the chocolate being moved. But 3-year-olds typically claim that Maxi will look in the second cupboard, because the children know that this is where the chocolate really is. Children are able to provide the right answer to this question somewhere between the ages of 4 to 6 (Callaghan et al., 2005), and children in some cultures are able to do it earlier than children in others (Liu et al., 2008).

Although very young children do not fully understand that others have different perceptions or beliefs than they do, they do seem to understand that others have different desires. For example, a 2-year-old who likes dogs can understand that other children don’t like dogs and can correctly predict that other children will avoid dogs that the child herself would approach. When 18-month-old toddlers see an adult express disgust while eating a food that the toddlers enjoy, they hand the adult a different food, as if they understand that different people have different tastes (Repacholi & Gopnik, 1997).

Eventually, the vast majority of children come to understand that they and others have minds and that these minds represent the world in different ways. Once children understand these things, they are said to have acquired a theory of mind, which is the understanding that other people’s mental representations guide their behavior. The age at which children acquire a theory of mind appears to be influenced by a variety of factors, such as the number of siblings the child has, the frequency with which the child engages in pretend play, whether the child has an imaginary companion, and the socioeconomic status of the child’s family. But of all the factors researchers have studied, language seems to be the most important (Astington & Baird, 2005). Children’s language skills are an excellent predictor of how well they perform on false-belief tasks (Happé, 1995). Language—and especially language about thoughts and feelings—is an important tool for helping children make sense of their own and others’ minds (Harris, de Rosnay, & Pons, 2005).

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Two groups of children lag far behind their peers in acquiring a theory of mind. Children with autism (a disorder we’ll cover in more depth in the Disorders chapter) typically have difficulty communicating with other people and making friends, and some psychologists have suggested that this is because they have trouble acquiring a theory of mind (Frith, 2003). Although children with autism are typically normal on most intellectual dimensions—and sometimes far better than normal—they have difficulty understanding the inner lives of other people (Dawson et al., 2007). They do not seem to understand that other people can have false beliefs (Baron-Cohen, Leslie, & Frith, 1985; Senju et al., 2009), and they have special trouble understanding belief-based emotions such as embarrassment and shame (Baron-Cohen, 1991; Heerey, Keltner, & Capps, 2003). The second group of children who lag behind their peers in acquiring a theory of mind consists of deaf children whose parents do not know sign language. These children are slow to learn to communicate because they do not have ready access to any form of conventional language, and this restriction seems to slow the development of their understanding of other minds. Like children with autism, they display difficulties in understanding false beliefs even at 5 or 6 years of age (DeVilliers, 2005; Peterson & Siegal, 1999). Just as learning a spoken language seems to help hearing children acquire a theory of mind, so does learning a sign language help deaf children do the same (Pyers & Senghas, 2009).

Cognitive development is a complex journey, and Piaget’s ideas about it were nothing short of groundbreaking. Few psychologists have had such a profound impact on the field. Many of these ideas have held up quite well, but in the last few decades, psychologists have discovered two general ways in which Piaget got it wrong. First, Piaget thought that children graduated from one stage to another in the same way that they graduated from kindergarten to first grade: A child is in kindergarten or first grade, he is never in both, and there is an exact moment of transition to which everyone can point. Modern psychologists see development as more fluid and continuous—a less steplike progression than Piaget believed. Children who are transitioning between stages may perform more mature behaviors one day and less mature behaviors the next. Cognitive development is more like the change of seasons than it is like graduation. Second, children acquire many of the abilities that Piaget described much earlier than he realized (Gopnik, 2012). Every year, clever researchers find new ways of testing infants and children, and every year, textbook authors must lower the age at which cognitive milestones are achieved.

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Discovering Our Cultures

Piaget saw the child as a lone scientist who made observations, developed theories, and then revised those theories in light of new observations. And yet, most scientists don’t start from scratch. Rather, they receive training from more experienced scientists. According to Piaget’s contemporary, the Russian psychologist Lev Vygotsky, children do much the same thing. Vygotsky believed that cognitive development was largely the result of the child’s interaction with members of his or her own culture rather than his or her interaction with concrete objects (Vygotsky, 1978).

For example, in English, the names of numbers beyond 20 follow a logical pattern: twenty followed by a digit (twenty-one, twenty-two, twenty-three, etc.). In Chinese, the numbers from 11 to 19 follow the same rule (ten-one, ten-two, ten-three …), but in English they do not (eleven, twelve, thirteen …). The difference in the regularity of these two systems makes a big difference to the children who must learn them. It is obvious to a Chinese-speaking child that 12 is 10+2 because the number is actually called “ten-two,” but this fact is not so obvious to an English-speaking child, who calls the number “twelve” (see FIGURE 10.4). In one study, children from many countries were asked to hand an experimenter a certain number of bricks. Some of the bricks were single, and some were glued together in strips of 10. When Asian children were asked to hand the experimenter 26 bricks, they tended to hand over 2 strips of 10 plus 6 singles. Non-Asian children tended to use the clumsier strategy of counting out 26 single bricks (Miura et al., 1994). Results such as these suggest that the regularity of the counting system that children inherit can promote or discourage their discovery of the fact that two-digit numbers can be broken down (Gordon, 2004; Imbo & LeFevre, 2009).

Counting is just one of the many things that children learn from others. In fact, human beings are better than any other animal on earth at learning from other members of their own species, and that’s because they have three important skills that most other animals lack (Meltzoff et al., 2009; Striano & Reid, 2006).

Joint attention (“I see what you see”), imitation (“I do what you do”), and social referencing (“I think what you think”) are three of the basic abilities that allow infants to learn from other members of their species.

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Unlike baby turtles, baby humans cannot survive without their caregivers. But what exactly do caregivers provide? Some obvious answers are warmth, safety, and food—and those obvious answers are right. But caregivers also provide something that is far less obvious but every bit as essential to an infant’s development.

During World War II, psychologists studied infants who were living in orphanages while awaiting adoption. Although these children were warm, safe, and wellfed, many were developmentally impaired, both physically and psychologically (Spitz, 1949). A few years later, psychologist Harry Harlow (1958; Harlow & Harlow, 1965) discovered that infant rhesus monkeys that were warm, safe, and well fed but that were not allowed any social contact for the first 6 months of their lives developed a variety of behavioral abnormalities. They compulsively rocked back and forth while biting themselves, and if they were introduced to other monkeys, they avoided them entirely. These socially isolated monkeys turned out to be incapable of communicating with or learning from others of their kind, and when the females matured and became mothers, they ignored, rejected, and sometimes even attacked their own infants. Harlow also discovered that when socially isolated monkeys were put in a cage with two “artificial mothers”—one that was made of wire and dispensed food and one that was made of cloth and dispensed no food—they spent most of their time clinging to the soft cloth mother despite the fact that the wire mother was the source of their nourishment. Clearly, infants of both species require something more from their caregivers than mere sustenance. But what?

Becoming Attached

Few things are cuter than a string of ducklings following their mother. But how do they know who their mother is? In a series of studies, the biologist Konrad Lorenz discovered that ducklings don’t actually know who their mothers are at all. Rather, they simply follow the first moving object they see after they are born—even if that object is a tennis ball or a biologist! Lorenz theorized that nature designed ducklings so that the first moving object they saw was imprinted on their brains and became “the thing I must always stay near” (Lorenz, 1952).

Psychiatrist John Bowlby was fascinated by Lorenz’s work, as well as by Harlow’s studies of rhesus monkeys reared in isolation and the work on children reared in orphanages, and he sought to understand how human infants form attachments to their caregivers (Bowlby, 1969, 1973, 1980). Bowlby began by noting that from the moment they are born, ducks waddle after their mothers and monkeys cling to their mothers’ furry chests because the newborns of both species must stay close to their caregivers to survive. Human infants, he suggested, have a similar need, but because they are much less physically developed, they can’t waddle or cling. So instead they smile and cry. When an infant cries, gurgles, coos, makes eye contact, or smiles, most adults reflexively move toward the infant, and Bowlby suggested that this is why infants have been designed to emit these signals.

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According to Bowlby, infants initially send these signals to anyone within visual or auditory range. For the first 6 months or so, they keep a “mental tally” of who responds most promptly and often to their signals, and soon they begin to target the best and fastest responder, also known as the primary caregiver. This person quickly becomes the emotional center of the infant’s universe. Infants feel secure in the primary caregiver’s presence and will happily crawl around, exploring their environments with their eyes, ears, fingers, and mouths. But if their primary caregiver gets too far away, infants begin to feel insecure, and they take action to decrease the distance between themselves and their primary caregiver, perhaps by crawling toward their caregiver or perhaps by crying until their caregiver moves toward them. Human infants, Bowlby suggested, are predisposed to form an attachment—that is, an emotional bond with a primary caregiver.

Attachment Styles

Of course, not all emotional bonds are of the same kind. Research suggests that most infants show one of four basic patterns of attachment, known as attachment styles (Ainsworth et al., 1978), which can be inferred by watching how they respond when their caregivers leave them alone for a few minutes and then return:

Where do these attachment styles come from? Childrens’ attachment styles are determined in part by their temperament, or characteristic pattern of emotional reactivity (Thomas & Chess, 1977). Whether measured by parents’ reports or by physiological indices such as heart rate or cerebral blood flow, very young children vary in their tendency toward fearfulness, irritability, activity, positive affect, and other emotional traits (Rothbart & Bates, 1998). These temperamental differences among infants appear to result partly from innate biological differences (Baker et al., 2013). But culture also plays a role in determining attachment style. For example, although the secure attachment style is the most common one among infants of all cultures (van IJzendoorn & Kroonenberg, 1988), German children (whose parents tend to foster independence) are more likely to have avoidant than ambivalent attachment styles, and Japanese children (whose mothers typically stay home and do not leave them in the care of others) are more likely to have ambivalent than avoidant attachment styles (Takahashi, 1986).

Although biology and culture both play a role, for the most part a child’s attachment style is determined by interactions with his or her primary caregiver. Studies have shown that mothers of securely attached infants tend to be especially sensitive to signs of their child’s emotional state, especially good at detecting their infant’s “request” for reassurance, and especially responsive to that request (Ainsworth et al., 1978; De Wolff & van IJzendoorn, 1997). In contrast, mothers of infants with an ambivalent attachment style tend to respond inconsistently, only sometimes attending to infants who are showing signs of distress.

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As a result of their interactions with their caregivers, infants develop an internal working model of relationships, which is a set of beliefs about the self, the primary caregiver, and the relationship between them (Bretherton & Munholland, 1999). Secure infants seem certain that their primary caregiver will respond when they feel distressed; avoidant infants seem certain that their primary caregiver will not respond when they are distressed; and ambivalent infants seem uncertain about whether their primary caregiver will respond. Infants with a disorganized attachment style seem to be confused about their caregivers, which has led some psychologists to speculate that this style primarily characterizes children who have been abused (Carolson, 1998; Cicchetti & Toth, 1998).

Differences in how caregivers respond are largely due to differences in their ability to read their infants’ emotional states. Mothers who think of their infants as unique individuals with emotional lives and not just as creatures with urgent physical needs are more likely to have securely attached infants (Meins, 2003; Meins et al., 2001)? It appears so. Mothers whose infants were particularly irritable and difficult participated in a training program designed to sensitize them to their infants’ emotional signals and to encourage them to be more responsive to their infants. A year or two later, those infants whose mothers had received the training were considerably more likely to have a secure attachment style than were those whose mothers did not receive the training (van den Boom, 1994, 1995).

This is potentially good news, because children and adults who were securely attached as infants have greater psychological well-being (Madigan et al., 2013) higher academic achievement (Jacobson & Hoffman, 1997), and better social relationships (McElwain, Booth-LaForce, & Wu, 2011; Schneider, Atkinson, & Tardif, 2001; Simpson, Collins, & Salvatore, 2011; Steele et al., 1999; Vondra et al., 2001). Some psychologists suggest that this is because people apply the working models they developed as infants to their later relationships with teachers, friends, and lovers (Sroufe, Egeland, & Kruetzer, 1990). But other psychologists argue that an infant’s attachment style is correlated with later outcomes only because both the style and the outcome are caused by the same environment: In other words, sensitive and responsive caregivers cause both the infant’s attachment style and his or her later adult outcomes (Lamb et al., 1985).

From the moment of birth, human beings can make one distinction quickly and well, and that’s the distinction between pleasure and pain. Before they hit their very first diapers, infants can tell when something feels good or bad, and they can demonstrate to anyone within earshot that they strongly prefer the former. Over the next few years, they begin to notice that their pleasures (“Throwing food is fun”) are often someone else’s pains (“Throwing food makes Mom mad”), which is a bit of a problem because infants need these other people (and especially their caregivers) to survive. So they start to learn how to balance their needs and the needs of those around them, and they do this in part by developing the distinction between right and wrong.

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Knowing What’s Right

How do children think about right and wrong? Piaget identified three ways in which children’s moral thinking shifts as they grow and develop (Piaget, 1932/1965).

Psychologist Lawrence Kohlberg used Piaget’s insights to produce a more detailed theory of the development of moral reasoning (Kohlberg, 1958, 1963, 1986). He based his theory on people’s responses to a series of dilemmas like this one:

A woman was near death from a special kind of cancer. The druggist in town had recently discovered a new drug that might save her. The druggist was charging $2,000 a dose, even though it only cost him $200 to make. The sick woman’s husband, Heinz, only had $1,000. He told the druggist that his wife was dying and asked him to sell the drug cheaper. But the druggist said: “No, I discovered the drug and I’m going to make money from it.” So Heinz got desperate and broke into the drugstore to steal the drug for his wife. Should Heinz have done that?

According to Kohlberg, people’s answers to this question reveal that moral reasoning develops in three stages:

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Research supports Kohlberg’s general claim that moral reasoning shifts from an emphasis on punishment to an emphasis on social rules and finally to an emphasis on ethical principles (Walker, 1988). But research also suggests that these stages are not quite as discrete as Kohlberg thought. For instance, a single person may use preconventional, conventional, and postconventional thinking in different circumstances, which suggests that the developing person does not “reach a stage” so much as “acquires a skill” that may or may not be used on a particular occasion. Others have criticized Kohlberg’s theory on the grounds that it doesn’t apply well to non-Westerners (Simpson, 1974). For example, some non-Western societies value obedience and community over liberty and individuality; thus, the moral reasoning of people in those societies may appear to reflect a conventional devotion to social norms when it actually reflects a postconventional consideration of ethical principles.

Feeling What’s Right

Research on moral reasoning suggests that people are like judges in a court of law, using rational analysis—sometimes simple and sometimes sophisticated—to distinguish between right and wrong. But moral dilemmas don’t just make us think; they also make us feel. Consider this one:

You are standing on a bridge. Below you see a runaway trolley hurtling down the track toward five people who will be killed if it remains on its present course. You can save these people by flipping a lever that will switch the trolley onto a different track, where it will kill just one person instead of five. Is it morally permissible to divert the trolley and prevent five deaths at the cost of one?

Now consider a slightly different version of this problem:

You and a large man are standing on a bridge. Below you see a runaway trolley hurtling down the track toward five people who will be killed if it remains on its present course. You can save these people by pushing the large man onto the track, where his body will be caught up in the trolley’s wheels and stop it before it kills the five people. Is it morally permissible to push the large man and prevent five deaths at the cost of one?

These scenarios are illustrated in FIGURE 10.6. If you are like most people, you are more likely to think it is morally permissible to pull a switch than to push a man (Greene et al., 2001). And yet, both cases involve killing one person to save five, so how did your moral reasoning lead you to reach such different conclusions? The answer is that you probably didn’t reach these conclusions by moral reasoning at all. Rather, you simply had a strong negative emotional reaction to the thought of pushing another human being into the path of an oncoming trolley and watching him get sliced and diced, and that emotional reaction instantly led you to conclude that pushing him must be wrong. Sure, you came up with a few good arguments to support this conclusion (“What if he turned around and bit me?” or “I’d hate to get spleen all over my new shoes”), but those arguments probably followed your conclusion rather than preceding it (Greene, 2013).

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The way people respond to cases such as these has convinced some psychologists that moral judgments are the consequences—and not the causes—of emotional reactions (Haidt, 2001). According to this moral intuitionist perspective, we have evolved to react emotionally to a small family of events that are particularly relevant to reproduction and survival, and we have developed the distinction between right and wrong as a way of labeling and explaining these emotional reactions (Hamlin, Wynn, & Bloom, 2007). Some research supports this view. For example, in one study (Wheatley & Haidt, 2005), participants were hypnotized and told that whenever they heard the word take, they would experience “a brief pang of disgust … a sickening feeling in your stomach.” After they came out of the hypnotic state, the participants were asked to rate the morality of several actions. Sometimes the description of the action contained the word take (“How immoral is it for a police officer to take a bribe”) and sometimes it did not (“How immoral is it for a police officer to accept a bribe?”). Participants rated the action as less moral when it contained the word take, suggesting that their negative feelings were causing—rather than being caused by—their moral reasoning.

The moral intuitionist perspective suggests that we consider it immoral to push someone onto the tracks simply because the idea of watching someone suffer makes us feel bad (Greene et al., 2001). In fact, research has shown that watching someone suffer activates many of the same brain regions that are activated when we suffer ourselves (Carr et al., 2003; see the discussion of mirror neurons in the Neuroscience and Behavior chapter). In one study, women received a shock or watched their romantic partners receive a shock on different parts of their bodies. The regions of the women’s brains that processed information about the location of the shock were activated only when the women experienced the shock themselves, but the regions that processed emotional information were activated whether the women received the shock or observed it (Singer et al., 2004). The fact that we can actually feel another person’s suffering may explain why even a small child who is incapable of sophisticated moral reasoning still considers it wrong when someone hurts someone else, especially when the person being hurt is similar to the child (Hamlin et al., 2013). Indeed, even very young children say that hitting is wrong even when an adult instructs someone to do it (Laupa & Turiel, 1986). It appears that from a very early age, other people’s suffering can become our suffering, and this leads us to conclude that the actions that caused the suffering are immoral.

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