Newborns may appear to be capable of little more than squalling and squirming, but in the last decade, researchers have discovered that they are much more sophisticated than they appear. Infancy is the stage of development that begins at birth and lasts between 18 and 24 months and, as you will see, a lot more happens during this stage than meets the untrained eye.

New parents like to stand around the crib and make goofy faces at the baby because they think the baby will be amused. In fact, newborns have a rather limited range of vision. The level of detail that a newborn can see at a distance of 6.1 m (20 feet) is roughly equivalent to the level of detail that an adult can see at 183 m (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 20 to 50 cm (8 to 12 inches) away (about the distance between a nursing infant’s eyes and its mother’s face), newborns are visually quite responsive. How do we know what newborns are seeing? 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 as the frequency of exposure to that stimulus increases, and infants habituate just like the rest of us do. So what happened 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, newborns in one study were shown a circle, a circle with scrambled facial features, or a circle with a regular face. When the circle was moved across their fields of vision, the newborns tracked the circle by moving their heads and eyes—but they tracked the circle with the regular face longer than they tracked the others (Johnson et al., 1991). Newborns do more than simply track social stimuli. Researchers in one study 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. Infants are born 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 behaviour 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 as infants learn to execute more sophisticated motor behaviour.

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If reflexes disappear as more voluntary motor behaviour develops, does this mean that the reflexes interfere with voluntary motor behaviour (McGraw, 1943)? A simple study by McGill University researcher Phil Zelazo and his colleagues demonstrates that this is not the case (Zelazo, 1972, 1976; Zelazo, Zelazo, & Kolb, 1972). In fact, in at least one instance, an early “disappearing” reflex (the “stepping reflex” in which young babies reflexively “step” on a solid surface) appeared to facilitate later motor development. The researchers elicited the stepping reflex every day in a group of young infants. Not only did the stepping reflex not disappear along the “normal” developmental trajectory in these infants, but they developed voluntary walking earlier than untrained infants. The researchers concluded that the involuntary walking reflex could be transformed into voluntary walking (Zelazo, 1983).

The development of these more sophisticated behaviours tends to obey two general rules. The first is the cephalocaudal rule (or the “top-to-bottom” rule), which describes the tendency for motor skills 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 skills to emerge in sequence from the centre to the periphery. Infants learn to control their trunks before their elbows and knee, which they learn to control before their hands and feet (see FIGURE 11.2).

Motor skills generally emerge in an orderly sequence but not on a strict timetable. Rather, the timing of these skills 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). Furthermore, different infants seem to acquire the same skill in different ways. By closely following the development of four infants, one study examined how children learn to reach (Thelen et al., 1993). Two of the infants were especially energetic and initially produced large circular movements of both arms. To reach accurately, these infants had to learn to dampen these large circular movements by holding their arms rigid at the elbow and swiping at an object. The other two infants were less energetic and did not produce large, circular movements. Thus, their first step in learning to reach involved learning to lift their arms against the force of gravity and extend them forward. Detailed observations such as these suggest that, although most infants learn how to reach, different infants learn in different ways (Adolph & Avoilio, 2000).

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Infants can hear and see and move their bodies. But can they think? In the first half of the twentieth century, a Swiss biologist named Jean Piaget became interested in this question. He noticed that when confronted with difficult problems (Does the big glass have more liquid in it than the small glass? Can Billy see what you see?), children of the same age made roughly the same mistakes. And as they aged, they stopped making these mistakes 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 physical world works, (b) how their minds represent the world, and (c) how other minds represent the world. Let us see how children accomplish these three essential tasks.

Piaget (1954) suggested that cognitive development occurs in four stages: the sensorimotor stage, the pre-operational stage, the concrete operational stage, and the formal operational stage (see TABLE 11.1). The sensorimotor stage is the stage of cognitive development that begins at birth and lasts through infancy. As the word sensorimotor 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 the way the world works. For example, an infant sitting in a highchair might notice that every time he or she drops something, it falls to the floor. A bit later, the infant notices that a fistful of food does not make a sound when dropped, but when the spoon is dropped, it clatters. These consistent observations can lead to predictions (“When I drop this, I will hear a sound”), just like any other theory.

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As every scientist knows, the key advantage of having a theory is that one can use it to predict and control 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, 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 happens when 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. Infants’ theories about the world (“Things come closer if I pull them”) are occasionally disconfirmed, and so infants must occasionally adjust their schemas in light of their new experiences (“Aha! Only inanimate things come closer when I pull them”). Piaget called this accommodation, which happens when infants revise their schemas in light of new information.

What kinds of schemas do infants develop, apply, and adjust? 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 would not 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. Piaget noted that in the first few months of life, infants act as though objects stop existing the moment they are out of sight. For instance, he observed that a 2-month-old infant will track a moving object with her eyes, but once the object leaves her visual field, she will not search for it. Put the shoes in the closet and—poof!—they are gone!

Was Piaget right? As a general rule, when infants demonstrate an ability, then they definitely have it, but when they fail to demonstrate an ability, they may lack the ability or the test may not be sensitive enough to reveal it. Modern research shows that when other tests are used, infants can demonstrate their 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 11.3). 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. What did infants do? 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).

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Studies such as these suggest that infants do indeed have some understanding of object permanence by the time they are just 4 months old. For example, what do infants see when they look at the line labelled A in FIGURE 11.4? Adults see a continuous blue line that is being obstructed by the solid orange block in front of it. Do infants see line A as continuous and obstructed, or do they see it as two blue objects on either side of an orange object? Studies show that when infants are allowed to become familiar with line A, they are subsequently more surprised by line C than by line B, despite the fact that line C actually looks more like line A than does line B (Kellman & Spelke, 1983). This suggests that infants see line A as a continuous line. Infants clearly do not think of the world only in terms of its visible parts, and at a very early age they seem to “know” that objects continue to exist even when they are out of sight (Wang & Baillargeon, 2008).

Piaget (1927/1977, p. 199) wrote: “The child’s first year of life is unfortunately still an abyss of mysteries for the psychologist. If only we could know what is going on in a baby’s mind while observing him in action, we could certainly understand everything there is to psychology.” Although the mystery of the infant mind is still far from solved, it is no longer an abyss. Research has taught us a great deal about what infants do and do not know, and the general conclusion is that they know much more than Piaget (or their parents) ever suspected (Gopnik, 2012).

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The long period following infancy is called childhood, which is the period that begins at about 18 to 24 months and lasts until about 11 to 14 years. According to Piaget, children enter childhood at one stage of cognitive development and leave at another. They enter in the pre-operational 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 exit at 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. Pre-operational 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. Pre-operational 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 the quantitative properties of an object are invariant despite changes in the object’s appearance.

Why do pre-operational children not seem to grasp the notion of conservation? Piaget suggested that children have several tendencies that explain this mistake. For instance, centration is the tendency to focus on just one property of an object to the exclusion of all others. Whereas adults can consider several properties at once, children focus on the length of the line of eggs without simultaneously considering the amount of space between each egg. Piaget also suggested that children fail to think about reversibility. That is, they do not consider the fact that the operation that made the line of eggs longer could be reversed: The eggs could be repositioned more closely together, and the line would become shorter. Both of these tendencies make it difficult for the pre-operational child to recognize that a longer line of eggs does not necessarily mean more eggs.

But there is an even deeper reason why pre-operational children do not fully grasp the notion of conservation: 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 the subjective and the objective, between appearances and realities, between things in the mind and things in the world. We realize that things are not always as they seem: A wagon can be red but look grey at dusk, and a highway can be dry but look wet in the heat. We make a distinction between the way things are and the way we see them. Visual illusions delight us precisely because we know that they look like this but are really like that. Pre-operational children do not make this distinction. When something looks grey or wet, they assume it is grey or wet.

As children move from the pre-operational to the concrete operational stage, they have a major epiphany that will stay with them for the rest of their lives: The way the world appears is not necessarily the way the world really is. They realize that their minds represent—and hence can misrepresent—the objects in the world, and this enables them to solve problems that require them to ignore an object’s subjective appearance (cf. Deák, 2006). 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. They can understand that when a sponge is painted grey to look like a rock, it is still a sponge despite its appearance. 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.

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Once children are at the concrete operational stage, they can readily solve physical problems involving egg-spreading and clay-squishing. They learn to solve non-physical 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. People who move on to this stage (and Piaget believed that some people never did) are able to reason systematically about abstract concepts such as liberty and love and about hypotheticals and counterfactuals—about events that have not yet happened, and about events that might have happened but did not. There are no concrete objects in the world to which words such as liberating or loving refer, and yet people at the formal operational stage can think and reason about such concepts in the same way that a concrete operational child can think and reason about squishing and folding. The ability to generate, consider, reason about, or mentally “operate on” abstract objects, is the hallmark of formal operations.

As children develop, they discover their own minds, but they also discover the minds of others. Because pre-operational children do not fully grasp the fact that they have minds that mentally represent objects, they also do not fully grasp the fact that other people have minds that may mentally represent the same objects in different ways. As such, pre-operational children generally expect others to see the world as they do. 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. Egocentrism is the failure to understand that the world appears differently to different people. Egocentrism is a hallmark of the pre-operational stage and it reveals itself in a variety of interesting ways.

Just as 3-year-old children do not realize that other people do not see what they see, they also do not realize that other people do not know what they know. This fact has been demonstrated in hundreds of studies using the false-belief task (Wimmer & Perner, 1983). In the standard version of this task, 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 what the children saw, namely, that the chocolate was moved. But 3-year-olds typically claim that Maxi will look in the second cupboard. Why? Because that is where the children know the chocolate to be—and what they know, everyone knows! Children are able to do the false-belief task somewhere between the ages of 4 to 6 (Callaghan et al., 2005), and children in some cultures are able to do it it earlier than children in others (Liu et al., 2008).

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Some researchers believe that the false-belief task, like Piaget’s test for object permanence, does not allow very young children to demonstrate their true abilities, and several recent studies have shown that much younger children can indeed do modified versions of the false-belief task (Baillargeon, Scott, & He, 2010; Onishi & Baillargeon, 2005; Rubio-Fernandez & Geurts, 2012; Senju et al., 2011; Southgate, Senju, & Csibra, 2007). But it is not clear that very young children do these tasks the same way as older children do, namely, by truly understanding that other people can have beliefs that differ from their own (Apperly & Butterfill, 2009; Low & Watts, 2013). Whatever very young children are doing, their performances are impressive, and it seems clear that children begin to understand the nature of other minds much earlier than Piaget suspected.

Just as egocentrism affects children’s understandings of others’ minds, so does it affect their understanding of their own minds. In a classic study, University of Toronto researchers showed young children a box of Smarties and then opened it, revealing that it contained pencils instead of candy. Then the researchers closed the box and asked, “When I first showed you the box all closed up like this, what did you think was inside?” Although most 5-year-olds said Smarties, most 3-year-olds said pencils (Gopnik & Astington, 1988). For the 3-year-old child, a past self is like another person, and so the past self must have known what the child now knows.

Different people have different perceptions and beliefs. They also have different desires and emotions. Do children understand that these aspects of other people’s mental lives may also differ from their own? Surprisingly, even very young children who do not yet fully understand that others have different perceptions or beliefs do seem to understand that other people have different desires. For example, a 2-year-old who likes dogs can understand that other children do not 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). Interestingly, young children understand other people’s desires best when their own desires have already been fulfilled and are not competing for their attention (Atance, Bélanger, & Meltzoff, 2010).

In contrast, children take a much longer time to understand that other people may have emotional reactions unlike their own. When 5-year-olds hear a story in which Little Red Riding Hood knocks on her grandmother’s door, unaware that a wolf is inside waiting to devour her, they realize that Little Red Riding Hood does not know what they know; nonetheless, they expect Little Red Riding Hood to feel what they feel, namely, fear (Bradmetz & Schneider, 2004; DeRosnay et al., 2004; Harris et al., 1989). When asked where Maxi will look for the chocolate that was moved while Maxi was out of the room, they correctly say that Maxi will look in the original location, but they incorrectly say that Maxi feels sad. It is only at about 6 years of age that children come to understand that because they and others have different knowledge, they and others may also experience different emotions in the same situation.

Clearly, children have a whole lot to learn about how the mind works—and most of them eventually do. The vast majority of children ultimately 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 human behaviour is guided by mental representations.

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Most of us eventually acquire a theory of mind, but two groups of people are somewhat slower to do so. Children with autism (a disorder we will cover in more depth in the Psychological 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). Interestingly, until children acquire a theory of mind they are generally not susceptible to the phenomenon of “contagious yawning” (Platek et al., 2003), and in fact, people with autism are also less likely to “catch a yawn” (Senju et al., 2007).

The second group of children who lag behind their peers in acquiring a theory of mind is a subset of deaf children: those with parents who cannot communicate with them (either because the child has not received a cochlear implant, or because the 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). Learning a language, either spoken or signed, seems to help children acquire a theory of mind (Pyers & Senghas, 2009).

The age at which children acquire a theory of mind appears to be influenced by a variety of other 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). The way that caregivers talk to children is also a good predictor of how well children do these tasks. Perhaps not surprisingly, children whose caregivers frequently talk about thoughts and feelings tend to be good at understanding beliefs and belief-based emotions. Some psychologists speculate that children benefit from hearing psychological words such as want, think, know, and sad; others suggest that children benefit from the grammatically complex sentences that typically contain these psychological words; and some believe that caregivers who use psychological words are also more effective in getting children to reflect on mental states. Whatever the explanation, it is clear that 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).

Cognitive development is an amazing and 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 or she is never in both, and there is an exact moment of transition to which everyone with a clock or a calendar can point. Modern psychologists see development as more fluid and continuous: a less step-like progression than Piaget believed. Children who are transitioning between stages may perform more mature behaviours one day and less mature behaviours the next. Cognitive development is more like the change of seasons than it is like graduation.

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The second thing about which Piaget was mistaken was the ages at which these transitions occur. By and large, they happen earlier than he realized (Gopnik, 2012). For example, Piaget suggested that infants had no sense of object permanence because they did not actively search for objects that were moved out of their sight. But when researchers use experimental procedures that allow infants to “show what they know,” even 4-month-olds display a sense of object permanence. Piaget suggested that it takes many years until children can overcome their egocentrism enough to realize that others do not know what they know, but new experimental procedures have detected some evidence of this understanding in 13-month-old infants (Baillargeon et al., 2010). 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.

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 do not start from scratch. Rather, they receive training from more experienced scientists and they inherit the theories and methods of their disciplines. According to Russian psychologist Lev Vygotsky, children do much the same thing. Vygotsky was born in 1896, the same year as Piaget, but unlike Piaget, he 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 noted that cultural tools, such as language and counting systems, exert a strong influence on cognitive development (Vygotsky, 1978).

For example, in English, the numbers beyond 20 are named by a decade (twenty) that is followed by a digit (one) and their names follow a logical pattern (twenty-one, twenty-two, twenty-three, etc.). In Chinese, Japanese, and Korean, the numbers from 11 to 19 are similarly constructed (ten-one, ten-two, ten-three…). But in English, the names of the numbers between 11 and 19 either reverse the order of the decade and the digit (sixteen, seventeen) or are entirely arbitrary (eleven, twelve). 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—which is called “ten-two”—can be decomposed into 10 and 2, but it is not so obvious to an English-speaking child, who calls the number “twelve” (see FIGURE 11.5). 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 two strips of 10 plus six 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 decomposed (Gordon, 2004; Imbo & LeFevre, 2009).

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Of course, if you have ever tried to train a pet snake, you already know that not all species are well prepared to learn from others. Human beings are the champions in this regard, because we have three skills that make us nature’s most exceptional students (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 the three 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 well fed, many were developmentally impaired, both physically and psychologically, and nearly 40 percent died before they could be adopted (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 were not allowed any social contact for the first 6 months of their lives, developed a variety of behavioural 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 all these species require something more from their caregivers than mere sustenance. But what?

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When Konrad Lorenz was a child he became the proud owner of a duck, and he quickly noticed something very interesting. Several decades later, the thing he had noticed helped him win the Nobel Prize. As he explained in his acceptance speech, “From a neighbour, I got a one-day-old duckling and found, to my intense joy, that it transferred its following response to my person.” Ducklings normally follow their mother everywhere she goes, and what Lorenz discovered as a child (and then proved scientifically as an adult) is that new hatchlings will faithfully follow the first moving object to which they are exposed. If that object is a human being or a tennis ball, then the hatchling will ignore its mother and follow that object instead. Lorenz theorized that nature designed birds so that the first moving object they saw was imprinted on their brains as “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 they are much less physically developed than ducks or monkeys and therefore can neither waddle nor cling. What they can do is smile and cry. Because they do not have webbed feet or furry hands that allow them to stay close to their caregivers, they use what they do have to keep their caregivers close to them. 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.

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 often and most promptly 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 centre 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. Bowlby believed that all of this happens because evolution has equipped human infants with a social reflex that is every bit as basic as the physical reflexes that cause them to suck and to grasp. Bowlby called this social reflex attachment: the emotional bond that forms between newborns and their primary caregivers.

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Attachment theory emphasizes the importance of the emotional bond with a primary caregiver for a child’s emotional development. And yet, more than 60 percent of primary caregivers with children under 3 years of age in Canada work outside the home. What are the effects of day care on attachment? As you might expect, this has been a hot research topic for a few decades. In the 1980s, many studies examined the effects of day care on the development of babies. They focused on day care centres attached to universities, and no developmental differences were found between children in day care and those cared for at home. In fact, for children from disadvantaged backgrounds, day care seems to have been beneficial. Subsequent work indicated that the uniformly high quality of the day cares included in these early studies was key to the observed outcomes. In all centres, staff were carefully selected, trained, and stayed for several years; there were low infant to caregiver ratios; communication between parents and caregivers was good; and the programs were age-appropriate and well designed.

Does day care that is not of such high quality affect the development of infants? Research in this area is difficult to conduct, since in general more affluent, educated parents put their children in high-quality day cares, which poorer, less educated people cannot afford. Any differences observed between types of day care may be due to the different backgrounds of the children. But the consensus emerging from many studies, in a variety of countries is that, in general, the quality of day care is of paramount importance. If a child is in high-quality day care, an infant’s attachment to his or her parents is not affected. In general, greater prevalence of insecure attachment is only observed if care is of poor quality, is used for many hours a week, and then only if the primary caregiver is low in sensitivity and responsiveness to his or her infant.

Bowlby’s work was completed at a time (1930s to 1950s) and in a place (Great Britain) in which fathers worked, and mothers stayed home and looked after the children. Some of his views (like the idea that a baby forms a unique and special bond with a single primary caregiver) are probably the result of his time and place. Different situations, such as when the mother is not the primary caregiver, or when multiple adult caregivers are involved, have been accommodated into the attachment framework. What is undisputed in Bowlby’s contribution is the great importance of attachment to the normal emotional development of children.

Infants who are deprived of the opportunity to become attached experience a variety of negative consequences (Gillespie & Nemeroff, 2007; O’Connor & Rutter, 2000; Rutter, O’Connor, & the English and Romanian Adoptees Study Team, 2004). But even when attachment does happen, it can happen more or less successfully (Ainsworth et al., 1978). Psychologist Mary Ainsworth developed a way to measure this: Strange Situation is a behavioural test used to determine a child’s attachment style. The test involves bringing a child and his or her primary caregiver (usually the child’s mother) to a laboratory room and then staging a series of episodes, including ones in which the primary caregiver briefly leaves the room and then returns, while psychologists monitor the infant’s reaction. Research shows that those reactions tend to fall into one of four patterns known as attachment styles.

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Research has shown that a child’s behaviour in the Strange Situation in the laboratory correlates fairly well with his or her behaviour at home (Solomon & George, 1999) (see FIGURE 11.7). Nonetheless, it is not unusual for a child’s attachment style to change over time (Lamb, Sternberg, & Prodromidis, 1992). And although some aspects of attachment styles appear to be stable across cultures—secure attachment is the most common style all over the world (van IJzendoorn & Kroonenberg, 1988)—other aspects of attachment styles vary across cultures. For example, German children (whose parents tend to foster independence) are more likely to have avoidant than ambivalent attachment styles, whereas 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).

A child’s attachment style is determined in part by the child’s biology. Different children are born with different temperaments, or characteristic patterns 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 differences are unusually stable over time. For example, infants who react fearfully to novel stimuli—such as sudden movements, loud sounds, or unfamiliar people—tend to be more subdued, less social, and less positive at 4 years old (Kagan, 1997). These temperamental differences among infants appear to result from innate biological differences (Baker et al., 2013). For example, 10 to 15 percent of infants have a highly reactive limbic system (which, you may recall from the Neuroscience and Behaviour chapter, is a collection of brain regions including the amygdala that play an important role in emotional reaction). These infants thrash and cry when shown a new toy or a new person, and they become children who tend to avoid novel people, objects, and situations, and then adults who are quiet, cautious, and shy (Schwartz et al., 2003).

The infant’s biologically based temperament plays a role in determining his or her attachment style, but for the most part, attachment style is determined by the infant’s social interactions with his or her 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). Mothers of infants with an ambivalent attachment style tend to respond inconsistently, only sometimes attending to their infants when they show signs of distress. Mothers of infants with an avoidant attachment style are typically indifferent to their child’s need for reassurance and may even reject their attempts at physical closeness (Isabelle, 1993). As a result of all this, 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). Infants with different attachment styles appear to have different working models of relationships (see FIGURE 11.8). Specifically, infants with a secure attachment style act as though they are certain that their primary caregiver will respond when they feel insecure; infants with an avoidant attachment style act as though they are certain that their primary caregiver will not respond; and infants with an ambivalent attachment style act as though they are 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).

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If the caregiver’s responsiveness determines (in large part) the child’s working model, and if the child’s working model determines (in large part) the child’s attachment style, then what determines the caregiver’s responsiveness (see FIGURE 11.9)? Differences in how caregivers respond are probably due (in large part) to differences in their ability to read their infant’s emotional states. Caregivers who are highly sensitive to these signs are almost twice as likely to have a securely attached child as are mothers who are less sensitive (van IJzendoorn & Sagi, 1999). 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 infants who are securely attached (Meins, 2003; Meins et al., 2001). Although such data are merely correlational, there is reason to suspect that a mother’s sensitivity and responsiveness are a cause of the infant’s attachment style. For instance, researchers studied a group of young mothers whose infants were particularly irritable or difficult. When the infants were about 6 months old, half the mothers were randomly chosen to participate in a training program designed to sensitize them to their infants’ emotional signals and to encourage them to be more responsive. The results showed that when the children were 18 months, 24 months, and 3 years old, those 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).

Does an infant’s attachment style have any influence on his or her subsequent development? Children who were securely attached as infants do better than children who were not securely attached on a wide variety of measures, from their psychological well-being (Madigan et al., 2013) to their academic achievement (Jacobson & Hoffman, 1997) to the quality of their relationships (McElwain, Booth-LaForce, & Wu, 2011; Schneider, Atkinson, & Tardif, 2001; Simpson, Collins, & Salvatore, 2011; Steele et al., 1999; Vondra et al., 2001).

For example, in one study that tracked people from infancy to adulthood, researchers found that 1-year-old infants who displayed insecure attachment during the Strange Situation experienced more negative emotions when trying to resolve major relationship conflicts with their romantic partners at age 21 (Simpson et al., 2007). And 1-year-old infants who displayed secure attachment styles in the Strange Situation task went on to become adults who rebounded more quickly from conflicts with their romantic partners (Salvatore et al., 2011). Some psychologists have suggested that people apply the working models they developed as infants to their later relationships with teachers, friends, and lovers: In other words, attachment style causes infants to become more or less successful adults (Sroufe, Egeland, & Kruetzer, 1990). But other psychologists argue that an infant’s attachment style is correlated with subsequent outcomes only because both of these 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).

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From the moment of birth, human beings can make one distinction quickly and well, and that is the distinction between pleasure and pain. Before their bottoms hit their very first diapers, infants can tell when something feels good or bad, and 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 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 a distinction between right and wrong.

How do children think about right and wrong? Piaget had something to say about this too. He spent time playing games with children and quizzing them about how they came to know the rules of these games and what they thought should happen to children who broke those rules. By listening carefully to what children said, Piaget concluded that the child’s moral thinking develops in three important ways (Piaget, 1932/1965).

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Piaget’s observations about the development of moral thinking have generally held up quite well, although he once again seemed to overestimate the ages at which some of these transitions take place. For example, research shows that children as young as 3 years old do sometimes consider people’s intentions when judging the morality of their actions (Yuill & Perner, 1988). Psychologist Lawrence Kohlberg used Piaget’s insights to produce a detailed theory of the development of moral reasoning (Kohlberg, 1963, 1986). According to Kohlberg, moral reasoning proceeds through three basic stages. Kohlberg (1958) based his theory on people’s responses to a series of dilemmas such as this one:

A woman was near death from a special kind of cancer. There was one drug that the doctors thought might save her. It was a form of radium that a druggist in the same town had recently discovered. The drug was expensive to make, but the druggist was charging ten times what the drug cost him to make. He paid $200 for the radium and charged $2000 for a small dose of the drug. The sick woman’s husband, Heinz, went to everyone he knew to borrow the money, but he could only get together about $1000, which is half of what it cost. He told the druggist that his wife was dying and asked him to sell it cheaper or let him pay later. But the druggist said: “No, I discovered the drug and I am going to make money from it.” So Heinz got desperate and broke into the man’s store to steal the drug for his wife. Should the husband have done that?

On the basis of their responses, Kohlberg concluded that most children are at the preconventional stage, which is a stage of moral development in which the morality of an action is primarily determined by its consequences for the actor. Immoral actions are simply those for which one is punished, and the appropriate resolution to any moral dilemma is to choose the behaviour with the least likelihood of punishment. For example, children at this stage often base their moral judgment of Heinz on the relative costs of one decision (“It would be bad if he got blamed for his wife’s death”) and another (“It would be bad if he went to jail for stealing”).

Kohlberg argued that children are preconventional, but somewhere around adolescence they move to the conventional stage, which is a stage of moral development in which the morality of an action is primarily determined by the extent to which it conforms to social rules. People at this stage believe that everyone should uphold the generally accepted norms of their cultures, obey the laws of society, and fulfill their civic duties and familial obligations. They argue that Heinz must weigh the dishonour he will bring upon himself and his family by stealing (i.e., breaking a law) against the guilt he will feel if he allows his wife to die (i.e., failing to fulfill a duty). People at this stage are concerned not just about spankings and prison sentences but also about the approval of others. Immoral actions are those for which one is condemned.

Finally, Kohlberg believed that in adulthood, some adults (but not all) move to the postconventional stage, which is a stage of moral development in which the morality of an action is determined by a set of general principles that reflect core values, such as the right of freedom, equality, and diversity. When a behaviour violates these principles, it is immoral, and if a law requires these principles to be violated, then it should be disobeyed. For a person who has reached the postconventional stage, a woman’s life is always more important than a shopkeeper’s profits and so stealing the drug is not only a moral behaviour, it is a moral obligation.

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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 he “acquires a skill” that he may or may not use on a particular occasion.

The use of the male pronoun here is intentional. Because Kohlberg developed his theory by studying a sample of American boys, some critics have suggested that it does not describe the development of moral thinking in girls (Gilligan, 1982) or in non-Westerners (Simpson, 1974). The first of these criticisms has received little scientific support (Jaffee & Hyde, 2000; Turiel, 1998), but the second has. 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. Other critics have noted that, although a child’s level of moral reasoning is positively correlated with his or her moral behaviour (Blasi, 1980), the correlation is not strong, and this is particularly true when the moral behaviour involves doing a good deed rather than refraining from doing a bad deed (Haidt, 2001; Thoma et al., 1999). These critics suggest that how people reason about morality may be interesting in and of itself, but does not tell us very much about how people will behave in their everyday lives. But if moral reasoning does not determine moral behaviour, then what does?

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 do not just make us think; they also make us feel. Consider this one:

You are standing on a bridge. Below you can see a runaway trolley hurtling down the track toward five people who will be killed if it remains on its present course. You are sure that 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 can see a runaway trolley hurtling down the track toward five people who will be killed if it remains on its present course. You are sure that 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 11.10. If you are like most people, you concluded that is morally permissible to pull a switch but not to push a man (Greene et al., 2001). In both cases you had to decide whether to sacrifice one human life in order to save five, and in one case you said yes and in another you said no. How can moral reasoning yield such inconsistent conclusions? It cannot, and the odds are that you did not 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 killed by it, and that reaction instantly led you to conclude that pushing him was wrong. Sure, you may have come up with a few good arguments to support this conclusion (“What if he turned around and hurt?” or “I would hate to get blood on my new shoes”), but those arguments probably followed rather than preceded your conclusion (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 labelling and explaining these emotional reactions (Hamlin, Wynn, & Bloom, 2007). For instance, most of us think that incest disgusts us because it is wrong, but another possibility is that we consider it wrong because it disgusts us. Incest is a poor method for producing genetically viable offspring, and so nature may have selected for people who are disgusted by it. Our reasoning about the immorality of incest may be the consequence of that disgust and not its cause.

Some research supports the moral intuitionist perspective. For example, in one study, people who had brain damage that prevented them from experiencing normal emotions treated the two situations shown in Figure 11.10 identically, choosing in both cases to sacrifice one life to save five (Koenigs et al., 2007). In another 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.

All of this 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 the very same brain regions that are activated when we suffer ourselves (Carr et al., 2003) (see the discussion of mirror neurons in the Neuroscience and Behaviour 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). Similarly, the emotion-relevant brain regions that are activated when a person smells a foul odour are also activated when the person sees someone else smelling the foul odour (Wicker et al., 2003). Studies such as these suggest that our brains respond to other people’s expressions of suffering by creating within us the experience of suffering, and this mechanism may have evolved because it allows us to know instantly what others are feeling (de Waal, 2012). 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).

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This may also explain why our aversion to watching others suffer begins so early in childhood (Warneken & Tomasello, 2009). When adults pretend to hit their thumbs with a hammer, even very young children seem alarmed and will attempt to comfort them (Zahn-Waxler et al., 1992). Indeed, even very young children distinguish between actions that are wrong because they violate a social rule and actions that are wrong because they cause suffering. When asked whether it would be okay to leave toys on the floor in a school that allowed such behaviour, young children tend to say it would. But when asked whether it would be okay to hit another child in a school that allowed such behaviour, young children tend to say it would not (Smetana, 1981; Smetana & Braeges, 1990). 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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