Throughout the previous chapters, we've considered a number of things that help to make you the person you are. Your intelligence, skills, personality, emotions, motivations, and goals are all fundamental for who you are, but how did these come to be? How have you developed physically, cognitively, socially, and morally? How much will you remain the same and how much will you change in the years to come?

These are the questions that developmental psychologists consider in order to better understand how a person progresses through life. We've already seen several examples of theories related to development including Terman's longitudinal study of intelligence, Freud's psychosexual stages, assessments of the stability of personality traits over time, and the lasting impact of early experience in the Dutch Hunger Winter. So chances are you already have a good sense of some of the major themes and challenges of developmental research: Does development occur continuously or in stages? What changes over time and what remains the same? How do genes and environment interact in shaping development? In this chapter we'll look at development more closely and see how theorists have addressed these questions in order to understand development throughout the lifespan.

Erik Erikson (1902-1994) viewed the lifespan as a series of eight stages, each with its own psychosocial task to be resolved. The first four of these stages were influenced by Freud's Psychosexual Stages, while the next four focused on the challenges of adolescence and adulthood.

In the oral-sensory stage (from birth to about age 1) the infant's primary task is establishing basic trust, which Erikson believed was primarily related to feeding. The infant learns it can depend on others, and this carries a lasting effect for future social relationships. Next the infant moves to the muscular-anal stage, during which the psychosocial task concerns developing a sense of autonomy based on successful toilet training. In the locomotor-genital stage (from age 3-6) the child learns a sense of initiative and independence to explore the world. The fourth stage was a latency stage, lasting from age 6 until 12, during which the child learns a sense of competence or inferiority based primarily on successful schoolwork.

The remaining four stages begin around pubertypubertyThe period of sexual maturation during which a person becomes capable of reproduction. and continue through the rest of life. According to Erikson, the main goal of adolescence is for teenagers to develop a sense of identityidentityErikson's concept of a stable sense of self developed during adolescence — who one is and what one stands for. (rather than role confusion) and this mostly comes from their peer relationships. In early adulthood (18-40) the main task is to find intimacy through romantic relationships. Middle adulthood concerns becoming a productive member of society (or perhaps a reproductive member of society by having children) and contributing to future generations, which Erikson referred to as generativity. Finally, at maturity, (65+) a person's main task is to reflect on life and accept the choices made, resulting in either ego integrity (a life well-lived) or regret and despair.

While Erikson's theory provides a reasonable outline for the major challenges of life, we should remember that it is heavily based on certain lifestyles and societal norms (such as schooling, age for childbearing, etc.) and may not apply well to other cultures or individuals who don't follow these social scripts. How well a particular task is resolved is up to the individual, meaning that what constitutes success in identity or ego integrity may vary widely and there are not strict guidelines for assessing accomplishment. Now we'll make our way through the lifespan in more detail, considering the changes and developments that occur over time.

We'll begin our journey through the lifespan at the very beginning; conception, the joining of the smallest single human cell (the sperm) with the largest single human cell (the egg). This is the genetic lottery; of the approximately 200 million sperm released, just one will find its way into the egg. Many of these 200 million sperm aren't really contenders, as they have defects which prevent them from swimming and many others will fail to swim to the correct fallopian tube. But of about 200 that will come close, one will find the way and break through the surface of the egg. Once this occurs, the egg is sealed by the release of an enzyme which prevents other sperm from penetrating it.

The chromosomes from the sperm and the egg combine to form a single cell, known as a zygote. During the germinal stage, the first 2 weeks of the zygote's development, the zygote will travel down the fallopian tube and attach itself to the walls of the uterus. This is no easy task and more than half of all zygotes will not survive the trip, with male zygotes (XY) having an increased likelihood of failing.

Once a zygote has attached itself to the uterus it is referred to as an embryo and it enters the embryonic stage, which lasts from the 2nd to the 8th week. At this point, the embryo is only about one inch long (2.54cm) though it already has a beating heart and the beginnings of arms and legs. Thus far male and female zygotes have been developing in the same way, but during this stage an XY embryo will begin producing androgens (male hormones) which will cause it to develop into a male.

Around the 9th week of development, the embryo is beginning to develop a skeleton and muscles and is now referred to as a fetus. The fetal stage lasts from the 9th week until birth, though development certainly doesn't end there. Unlike many other species, humans are born with a brain that is only 25% of its eventual adult size. This accommodates the physical logistics of giving birth, but more importantly, it gives us greater adaptability because it allows learning and environment to play large roles in brain development.

When we think about the environment's role in development, we have to remember that environment doesn't begin at birth and experiences in the womb are considered environmental influence. The placenta is the organ which links the bloodstreams of the mother and her offspring and this connection means that mom's environment influences her offspring before birth. A teratogenteratogenAn environmental agent — drug, alcohol, disease, radiation — that can harm a developing fetus. (Latin for “monster-maker”) is a substance which can harm development. Possible teratogens include lead, mercury, viruses, tobacco, alcohol, and other potentially toxic substances. Heavy drinking by a mother during pregnancy can result in fetal alcohol syndromefetal alcohol syndromeA condition caused by prenatal alcohol exposure, characterized by facial abnormalities, growth deficits, and cognitive impairment. in the child, causing intellectual disability and characteristic facial features including smaller eyelid openings and a smooth philtrum, or ridge on the upper lip. Smoking during pregnancy (or even second-hand smoke) also has detrimental effects on the child, including low birth weight and attention and perception problems. The effects of teratogens highlight that early experiences in the womb can have lasting impact on a child's development. In fact, the child can also have lasting impact on the mother, as cells from the fetus can pass back into the mother's body through the placenta and remain for years or even decades, a phenomenon known as fetal microchimerism.

Prenatal development also includes learning, and there's evidence that a fetus learns to recognize its mother's voice during this time. In a study by Anthony DeCasper and Melanie Spence in 1986, expectant mothers read a story aloud twice a day during their last weeks of pregnancy and their infants later showed a preference for the sounds of that story over a novel stimulus.

At birth, the fetus has about 100 trillion cells is now an infant. The infancy stage lasts from birth until age 18-24 months, during which the infant shows rapid development of perceptual and motor skills.

Infants are born with reflexes; patterns of motor responses that are triggered by certain types of sensory stimulation. One such reflex is the rooting reflex. When an infant's cheek is touched, the infant will turn to move its mouth in that direction. This reflex helps the mother to feed the infant, and it is accompanied by a sucking reflex, in which an infant will suck an object placed in the mouth. As the infant's control improves in the first few months, the rooting reflex disappears and the sucking reflex becomes a voluntary behavior.

While we can't predict the exact timing of particular skills, the sequence in which motor skills emerge follows a fairly predictable pattern of developmental milestones, such as first crawling, standing, walking, etc. The development of motor skills follows two general rules. The cephalocaudal rule (Latin for “head to tail”) refers to the fact that motor control starts with head movements, then moves downward to the arms, then feet. The proximodistal rule (Latin “near to far”) refers to developing control of the trunk, followed by elbows and knees, then finally hands and feet.

It can be difficult to assess what an infant perceives, because an infant is unable to tell us. So how can we figure out what's going on in an infant's mind? One way is to use a technique developed by Robert Fantz known as preferential looking (or visual preference), which is based on the idea that when given a choice between two stimuli, infants will look at the one they prefer or find more interesting. For example, if shown two tiles, one which is a solid color and one which is striped, infants will generally prefer to look at the striped tile. This technique can be used to estimate visual acuity at different distances by seeing when an infant can distinguish a solid tile from a thinly-striped one. Initially, clear vision seems to be limited to a distance of about one foot; not surprising when we consider that is roughly the distance to the mother's face when nursing. Experiments with preferential looking also reveal that infants prefer to look at certain types of stimuli, such as human faces.

A related technique is known as habituation. Habituation is based on the fact that we respond strongly to new stimuli and less intensely to repeated stimuli. This means we can see whether an infant considers a stimulus to be novel based on the strength of response. For example, we could see if an infant is able to differentiate two colors by showing one colored tile repeatedly until habituation occurs (response strength decreases). Then we could change the color of the tile and present it again. If the infant stares longer at this new tile, this tells us that the infant has noticed the change. Later we'll see how habituation has been used for more elaborate testing of what infants know about the world.

When thinking back on early years, most people find it impossible to remember much before about the age of 3. Infant brains just don't seem to have the capacity to store episodic memories yet, resulting in this infantile amnesia. Sometime around age 3, however, our brains become capable of storing autobiographical memories. This is also when our cognitive development really hits its stride, and we begin making rapid progress in a number of areas. In fact, from age 3 to age 6, children grow billions more synaptic connections than their brains actually use. This ensures that needed connections will be there, and part of normal development is the loss of neurons and neural connections which are not being used (known as synaptic pruning).

Mark Rosenzweig, David Krech, Edward Bennett, and Marian Diamond conducted research examining the role of environment on brain development in rats. By measuring the brains of rats who were raised in either an impoverished environment (an empty cage) or an “enriched” environment (a cage with toys, ladders, wheels, and tunnels), they could assess the influence of environment. They found that rats raised in the “enriched” environment had larger brain volume and a greater number of synapses.

This research is probably partially responsible for the onslaught of baby games, toys, and supposed enrichment programs. But how much do these things really enrich a human infant's environment? Probably not much. In the case of the rats, rather than thinking of the wheels and ladders as enriching, these were probably more like a rat's natural environment than the empty cage. “Enrichment” is probably not the best word and maybe something like “less impoverished” would be more accurate. It's likely that the best way to give a rat a bigger brain is not to put it in a cage with toys but to allow the rat to roam free and receive all the stimulation and enrichment the natural environment provides.

So before we rush out to buy Mozart CDs and baby yoga DVDs, we should consider that perhaps the natural environment of sights, sounds, language, and tactile experience is so wildly stimulating that it is already “enriched”. If you're currently raising your child in a featureless cage, then sure, throwing in a toy or two would probably help. But in the real world a child is already tackling tough problems; learning to interact, figuring out how language works, coordinating movements and so much more. Given the richness of any normal environment, some background music and another colorful toy probably aren't going to make much difference.

Swiss biologist-turned-developmental-psychologist Jean Piaget (1896-1980) investigated cognitive development, examining how cognitive abilities progressed throughout childhood. While assessing intelligence in young children, Piaget noticed that the mistakes children made weren't random and certain types of errors were common at certain ages, then seemed to suddenly disappear. This led Piaget to create a stage-based theory of cognitive development, with progress occurring in steps.

Piaget viewed children as little scientists who were building up structures for their knowledge (known as schemaschemaPiaget's term for a mental framework or concept used to organize and interpret information.) which were then maintained or adjusted based on new experiences. Piaget proposed that when children encounter new information, there is a process of either assimilationassimilationIncorporating new information into an existing schema without changing the schema.; adding the information to their existing schema, or accommodationaccommodationAdjusting or creating a new schema to incorporate information that doesn't fit existing schemas.; changing the schema to account for the new information.

For instance, after seeing a sparrow and being told it is a “bird”, a child might develop a schema that small flying things are called “birds”. When encountering a pigeon, the child can easily assimilate this new stimulus into the existing schema for “bird”. When seeing a bat, however, the child will need to accommodate, modifying the schema to distinguish that some small flying things are not birds.

The first of Piaget's stages is the sensorimotor stage, during which the infant's progress is primarily based on learning how to take in sensory information and how to control body movements. A fundamental concept Piaget believed was learned during this stage is object permanenceobject permanenceThe understanding that objects continue to exist even when out of sight — develops in Piaget's sensorimotor stage.. This is the notion that objects continue to exist even when we can no longer see them. Piaget thought that infants in the sensorimotor stage weren't able to understand this concept, explaining why they make certain types of errors or why a game of peekaboo is enthralling for infants but rather boring for anyone else.

Possible evidence that infants lack object permanence can be seen in the A-not-B error. After an object is repeatedly hidden in one location (A) an infant learns to reach for it in that location. Then the infant watches as the object is hidden in a new location (B). Despite watching closely, the infant will then reach for the object where it was last found (A) rather than where he watched it go (B). This suggests that the infant doesn't yet understand how the physical world functions.

Another possible interpretation of the A-not-B error is that infants are not yet able to control and coordinate their movements, since they often look at the B location while their arms reach for A, indicating that they know where the object is but are unable to inhibit the previously learned motor pattern. This suggests that improvement on the task might not be from improved understanding of object permanence, but from improved ability to suppress previously learned responses (part of what is known as executive function).

Piaget believed that infants lacked an understanding of object permanence until about age 2, but research using habituation and preferential looking has suggested that object permanence may exist considerably earlier. Renee Baillargeon, Elizabeth Spelke, and Stanley Wasserman found that 5-month-old infants stared longer at an impossible event than a possible event. In this study, infants seemed surprised when a box failed to stop the movement of a rotating panel, even though the infants could not actually see the box at the time (because it was behind the panel).

This suggests that infants knew the box still existed and expected it to stop the panel's movement. This experiment and others by Baillargeon and Spelke support the view that infant understanding of the physical world is more advanced than Piaget supposed. Similar research by Karen Wynn has found that infants may even have a sense of number. In one experiment, infants were shown 2 dolls which were then hidden behind a screen. A hand reached behind the screen and removed one doll. When the screen was lowered, there were still 2 dolls, and infants as young as 5 months responded to this impossible event by staring longer.

Before age 2 infants also show evidence that they are beginning to develop a sense of self-concept. Around 18 months is when children first pass the mark test and recognize their own reflections in a mirror (for details see the chapter on consciousness). As children continue to develop, their self-concept becomes more and more complex and they begin to form an identity which includes understanding of their gender, the groups they belong to, and how their traits and skills compare to those of others.

Around age 2, children are in the preoperational stage, because they don't yet fully understand how the physical world operates. Their perceptual and motor skills will, of course, continue to develop, but now there is greater focus on understanding the world, rather than just perceiving it and moving through it.

One common failure at this stage is difficulty with the concept of conservationconservationThe understanding that quantity remains the same despite changes in appearance — develops in the concrete operational stage.. Piaget tested this by using chunks of clay, taking two equal-sized chunks, then rolling one out into a long strip. Though children had initially agreed the pieces were equal, those in the preoperational stage now believed that the longer piece contained more clay. This failure to understand that quantity is conserved even when form changes applies to other situations as well, such as pouring equal amounts of liquid into different-shaped glasses or spreading out a row of objects on a table. Piaget thought the cause of this error was that children weren't yet able to interrelate their schema. In the case of liquid in a glass, children might know that height and width are each important, but they aren't yet able to connect these two schema and so they base their answers on just one.

In addition to figuring out how the world works, children in the preoperational stage also begin to develop a theory of mindtheory of mindThe ability to understand that others have mental states (beliefs, desires, intentions) different from one's own. to learn how others see the world. Around age 2 or 3, children show egocentrismegocentrismIn Piaget's theory, the inability to perceive things from others' perspectives — characteristic of the preoperational stage., meaning that they are unable to see the world from any viewpoint except their own. Children don't yet understand that other people can have different knowledge, thoughts, and ideas. Piaget demonstrated this by having children view small objects placed on opposite slopes of a model mountain. Despite first-hand experience that the viewpoints differed, children still reported that a viewer on the other side of the mountain could see the objects on the child's side.

Another way of demonstrating egocentrism is through a false-belief test, in which characters have different levels of knowledge of a situation. In the Sally-Anne test, two dolls, Sally and Anne, are used. The child watches as Sally places a marble in her basket, then leaves the room, so Sally doesn't see Anne move the marble to Anne's basket. Sally then returns, and the child is asked where Sally will look for the marble. Before about age 4, children frequently respond that Sally will look where Anne has hidden the marble, failing to recognize that Sally has no knowledge of Anne moving it.

This might explain the brutal honesty of young children; if you think everyone already knows what you know, there's no need to lie. Once children begin to understand that they can keep secrets, they also realize that they can manipulate the thoughts of others. Evidence for this can be seen in a study conducted by Joan Peskin. In this study, a “mean monkey” puppet asks children which of 2 stickers they want, then, always having first choice, the monkey takes it. Children aged 3 are repeatedly disappointed, as they always tell the monkey which sticker they really want, and so the monkey always takes it and leaves the children with the undesirable sticker. By about age 4 or 5, however, children are able to strategically deceive the monkey about what they want, telling him they want the undesirable sticker so he'll take it, leaving them with the one they really desire. This suggests that children realize they can have thoughts the monkey doesn't know about, and now they can imagine the monkey's viewpoint in order to deceive him. This task may also be related to the development of executive function, because success requires children to inhibit revealing which sticker they really want when they are asked.

Autism spectrum disorder refers to a range of developmental problems related to language, motor skills, and socialization. Autism is sometimes considered a kind of impaired theory of mind, in which sufferers (mostly boys) show less interest in people, are less aware of the emotions, intentions, and beliefs of others, and have difficulty recognizing and expressing emotions. The Sally-Anne task mentioned above has been used by Simon Baron-Cohen (cousin of Borat actor Sacha Baron-Cohen) and colleagues to assess theory of mind in children with autism, though it's important to note that some children with autism can pass the test, and some children without autism can fail, so results should not be seen as conclusive.

Many children with autism also suffer some degree of intellectual disability and despite depictions in popular culture, only a very small number of autistic children show enhanced skills in areas such as music or mathematics. Autism was initially considered rare, (Baron-Cohen et al suggesting it affected 1 in 2500 children in 1985) but diagnoses have risen dramatically, with some recent estimates as high as 1 in 68 children. This has caused alarm of an autism epidemic as well as accusations of misdiagnosis, with some researchers suggesting that autism has become a catch-all diagnosis for a number of unrelated developmental difficulties, ranging from slower language abilities to low empathy or even frequent tantrums.

Once children have come to understand how the physical operations of the world work, Piaget considered them to be in the concrete operational stage, some time around age 6. Children understand concepts of conservation and recognize that others have different views of the world, but they still struggle with abstract concepts. Children in this stage have difficulty with hypothetical situations and predicting how things will happen given certain abstract rules. Research by Judy DeLoache has shown that at this age children also struggle with tasks involving symbolic representation such as using a model of a room with a miniature toy hidden behind a small couch to determine the location of the toy in the actual room being modeled.

Eventually children develop the ability to think abstractly, entering Piaget's final stage: the formal operational stageformal operational stagePiaget's final stage (~12+ years) characterized by abstract reasoning and hypothetical thinking. (though Piaget thought some individuals never reach this stage). In this stage, usually beginning around age 11 and continuing throughout the lifespan, children have learned how to think about abstract concepts (such as democracy) and they are able to engage in if-then thinking; such as imagining ways things might happen in the future based on hypothetical changes now.

While Piaget's stages are able to provide a fairly accurate description of when certain skills emerge in children, they don't really explain how children jump from one stage to the next. Lev Vygotsky (1896-1934), a Russian developmental psychologist, focused on how social interaction influences a child's development. Vygotsky emphasized a zone of proximal developmentzone of proximal developmentVygotsky's concept of the gap between what a learner can do alone and what they can do with guidance. which referred to the skills just outside of a child's ability. These are the things that a child cannot do independently, but can accomplish with a little bit of help from a parent or peer. Rather than figuring things out on their own, children have a social environment where others provide scaffoldingscaffoldingVygotsky's term for the support provided by a more capable person that enables a learner to accomplish tasks beyond their current ability. to support the direction of their growth. Vygotsky's early death from tuberculosis meant that he was unable to fully complete his work but the concept has been developed and modified by later researchers.

Recognizing the importance of interaction brings us to another important aspect of a child's development; the development of social skills. How do children learn to connect with others?

One of the first human connections a child makes is with a primary caregiver, usually the mother. How does this connection (known as attachmentattachmentA strong emotional bond between an infant and their primary caregiver, providing a secure base for exploration.) between mother and child occur?

In some species, the development of this connection isn't left to chance and is hard-wired into the offspring. Konrad Lorenz is considered one the fathers of the field of ethology; the study of animal behavior. He shared the Nobel Prize in 1973 (along with ethologists Nikolaas Tinbergen and Karl von Frisch) for work on animal instincts, including a phenomenon known as imprintingimprintingLorenz's concept of the critical-period process by which young animals form an attachment to the first moving object they see.. Lorenz found that upon hatching, goslings would follow the first large moving object they see. There seems to be a critical periodcritical periodA developmental window during which specific experiences are necessary for normal development. of about 12 hours after hatching when this imprinting will occur. In nature, the first large moving object seen would be the mother, though Lorenz was able to have goslings attach to other animals, rolling balls, and even himself.

What about other species? Rather than waddling behind, young rhesus monkeys will cling to the fur of their mothers, a literal form of attachment. In the 1950s, Harry Harlow was conducting research with rhesus macaques when he discovered that monkeys raised in isolation would cling to cloth diapers as a source of comfort. Harlow decided to raise young monkeys with two surrogate “mothers”; a wire mother which provided food and a cloth mother which did not. This would help to determine whether attachment was due to the mother being a source of food (as many behaviorists believed) or a source of contact comfortcontact comfortHarlow's finding that infants attach to soft, comforting figures — not merely those that provide food.. Comfort won, as young monkeys spent most of their time clinging to the “fur” of the cloth mother and would run to this cloth mother when frightened. This suggested that the monkeys had emotionally attached to the cloth mother and were using it as a source of security and comfort.

Harlow's experiments are controversial due to the extent of mistreatment of the young monkeys and Harlow's cold writing style didn't help, as primatologist Robert Sapolsky described “I remember as a student being moved to tears of rage by the savage indifference of his writing”. Harlow's other studies included complete isolation in what he called the “pit of despair” and caused psychological disturbance in the monkeys. Harlow's brutality encouraged activists to oppose animal experimentation in order to prevent the type of suffering inflicted on these monkeys. On the bright side, however, these studies improved understanding of how abusive environments and social isolation can inflict psychological damage that continues through life. They also provided clear demonstrations of the importance of touch and comfort for healthy development, overturning earlier parenting advice which had urged parents not to touch or hold their infants too often.

Human infants aren't able to follow their mothers immediately after birth, and they aren't able to physically cling to their mothers either (though they do show a remnant of this with a grasp reflex; gripping an object which touches the palm tightly enough to briefly support their own body weight). But infants do still form an attachment in the form of an emotional bond. By crying, cooing, making eye contact, and smiling, human infants are able to connect with others and they track who regularly responds to these cues. This is usually the primary caregiver, and the infant will attach to this figure, using him or her as a secure base. This concept of a secure base is that the infant feels more comfortable exploring the environment in the presence of this person. When frightened or unsure, the infant has learned it can rely on this caregiver to provide assistance.

Mary Ainsworth tested the quality of this attachment by placing infants in a strange situation in which their secure base was no longer present. While a researcher observed through a one-way mirror, the mother would play with the infant, then exit the room, leaving the infant either alone or, in some variations, with a stranger. After waiting a few minutes to observe the infant's response, the mother would return to the room and the infant's reaction to this reunion would also be observed.

Ainsworth then classified the response styles of the infants as a secure attachmentsecure attachmentAn attachment style characterized by trust and confidence in the caregiver's availability and responsiveness., an avoidant attachmentavoidant attachmentAn attachment style characterized by little distress at separation and avoidance of the caregiver on reunion., or an ambivalent attachment (though about 5% of responses don't fit any of these styles and are thus considered disorganized attachment).

In a secure attachment, the infant shows distress when the caregiver leaves, but is then effectively comforted upon the caregiver's return. This is the most common attachment type, seen in about 60% of American children. About 20% show an avoidant attachment (also known as insecure-avoidant); they don't show distress when the caregiver leaves and therefore they don't seek comfort during the reunion. Approximately 15% of American children show an ambivalent attachment (also known as insecure-resistant) in which they are distressed when the caregiver leaves, yet the caregiver's return fails to provide comfort. These children may show anger and actively resist the caregiver's attempts at consolation.

After observing these responses from infants, we might naturally wonder what is causing these differences. In the personality chapter we considered that infants show the first signs of personality in their temperaments, or their patterns of emotional reactivity. Is attachment the first expression of a child's emerging personality? Or perhaps reactions demonstrate the infant's expectations for the caregiver's behavior; preparing for consolation, isolation, or confrontation. Or maybe the attachment type is the result of the parent's ability to read and understand the infant's emotional state, which may then depend on the infant's ability to clearly express that state. As with most questions we face, the answer is probably a mix of all of these factors and you can recall Bandura's reciprocal determinism to consider how temperament may influence and be influenced by experience and environment.

We should also keep in mind that these attachment types are not sharply-defined and may vary across cultures or change over time. Nevertheless, there are some outcomes associated with different attachment types. Secure attachment is associated with better social relationships and better future academic performance compared to ambivalent or avoidant attachments.

The possible influence of parenting doesn't end at attachment. Diana Baumrind classified parenting into 3 main styles: Authoritarian, Permissive, and Authoritative.

Authoritarian parentingAuthoritarian parentingA parenting style characterized by strict rules and high demands with little warmth or explanation. is strict, with clear rules and harsh punishments. What the parent says goes, and the child is powerless. This type of parenting has been associated with lower social skills and reduced self-esteem in children.

Permissive parentingPermissive parentingA parenting style characterized by high warmth and responsiveness but few rules or demands. is on the other end of the spectrum, with few or no rules or punishments. Children can do what they please and parents are neither demanding nor responsive. Children who receive this type of parenting have shown higher levels of aggression and lower levels of maturity.

Authoritative parentingAuthoritative parentingA parenting style combining warmth and responsiveness with clear structure and high expectations. falls in the middle of those extremes and describes parents who are demanding but are also responsive to the child. Rules are set and enforced, but with explanations for why the rules exist and open discussion and possible compromise based on the child's input. This type of parenting is associated with several positive outcomes including higher self-esteem, greater self-reliance, and better social competence.

Eleanor Maccoby and John Martin later added a fourth parenting style to Baumrind's trio, known as neglectful parenting (also known as uninvolved parenting), referring to parents who provide basic needs but are too preoccupied to be responsive or demanding of their children and instead focus most of their attention on other pursuits rather than parenting. This style has been associated with lower levels of social competence and lower school achievement.

As with attachment styles, the outcomes described above are correlational, so we can't assume causation. Children's traits may influence parenting style or children and parents may share genes related to social competence which influence their relationship.

How do we learn what is right and wrong? How do we gain an understanding of morality? Lawrence Kohlberg attempted to track the development of morality by posing ethical dilemmas to children and then analyzing the rationales for their answers. Based on interviews with thousands of children of different ages, Kohlberg formulated a stage-based approach for the development of moral reasoning. Kohlberg's model consists of 3 main stages of moral reasoning, each with 2 levels, for a total of 6 levels of moral developmentmoral developmentThe progression of reasoning about right and wrong — studied by Piaget, Kohlberg, and Gilligan..

While Kohlberg's theory is presented in stages, this doesn't necessarily mean that people always use the highest stage of moral reasoning they have reached and different problems and solutions may draw on arguments from earlier stages. Let's take a look at a moral dilemma which Kohlberg used, known as the Heinz Dilemma (not to be confused with a Heinz pickle). Here's the dilemma as used by Kohlberg (1981):

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 produce. He paid $200 for the radium and charged $2,000 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 $1,000 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'm going to make money from it.” So Heinz got desperate and broke into the man's laboratory to steal the drug for his wife. Should Heinz have broken into the laboratory to steal the drug for his wife? Why or why not?

Using this scenario, it doesn't matter whether respondents think that Heinz should or shouldn't have stolen the medicine, what matters is the moral reasoning behind the decision. With this in mind, let's look at each of Kohlberg's stages and consider how someone in each stage might address Heinz's dilemma.

In the preconventional stage, morality is generally framed in terms of consequences. Level 1 is a system of morality based entirely on punishment. If someone is punished, they must be wrong, and if they are not punished then their behavior must be ok. In Level 2, the emphasis is on gaining a reward. If you've been rewarded for something, then it must be good.

If you remember what we learned about the egocentrism of young children, you might not be surprised to see them think this way. After all, if you think that everyone knows what you know, then punishment or reward should always be swift and certain. No punishment must mean that others know what you did and don't have a problem with it.

Preconventional justifications would focus on whether or not Kohlberg would be rewarded or punished. One might argue that if he steals the drug and saves his wife then his action is justified, or one might argue that if he steals it and gets caught then it is not justified.

Rather than specific punishments or rewards, conventional moralityconventional moralityKohlberg's second level — reasoning based on social rules and maintaining order. focuses on societal approval. Consequences don't necessarily reveal morality because of the recognition that some rewards are undeserved and some deserved punishments are never received.

Level 3 morality focuses on conformity to group norms and social approval. Level 4 focuses on rigid codes for controlling behavior, such as systems of law and order or strict rules of etiquette.

Conventional explanations for Heinz would focus on societal expectations, systems of rules, or codes of conduct. So a level 3 justification for stealing the drug might be that Heinz must be a “good husband” and do anything possible to help his wife (and avoid social condemnation). At level 4, one might argue that stealing the drug is wrong because individuals must obey the law in order to maintain social order.

Kohlberg believed that most people never reached the last two levels of the postconventional stage but instead relied on the rules of society and codes of conduct to guide their moral reasoning (hence the label conventional). But for those who reach the postconventional stage, morality is based on overall ethical principles.

In level 5, rather than rigid adherence to rules, morality is based upon a “social contract” for the public good. Occasionally circumstances arise in which this contract requires flexibility in order to best serve the public interest. In level 6, the individual has come to a personal system of morality which is based on abstract ethical principles.

A response at level 5 might argue that laws don't exist simply to be obeyed; they serve to protect people. In this case, violating a law for something like theft is acceptable if doing so protects a human life. A level 6 argument against stealing the drug might be that Heinz is stealing not from the shopkeeper but from another potential patient. Who is Heinz to decide who lives or dies? Why should his wife's needs come before another patient with the same illness? One might argue that Heinz should see all human life as equally valuable and be glad that the drug will save someone, if not his wife.

These stages correspond to how a person thinks about behavior and aren't meant to imply that one level is more or less moral than another. Kohlberg's stages can be criticized for ignoring the role of culture in how people think about relationships, rules, and social order. Gender may also play a role, and Carol Gilligan has proposed that Kohlberg's stages are androcentric because males tend to emphasize justice in their moral reasoning, while females are more likely to focus on relationships and empathy for others. We should also remember that while responses might reveal how a person thinks about the dilemma, they don't necessarily reveal how the person would actually behave in a similar situation.

More recent psychologists such as Jonathan Haidt (pronounced height), have argued that in most cases, people don't carefully consider formal arguments when making decisions and instead they rely on moral intuitions, which are immediate and mostly unconscious evaluations of right or wrong. Later moral reasoning may be serving to rationalize or justify these feelings, rather than being part of the actual decision-making process.

So where do these moral intuitions come from? Rather than starting from scratch, it seems they use a clever evolutionary trick: emotional experiences developed for physical interactions in the world have been co-opted for use by our decision-making systems. So in terms of emotional response, our reaction to something like incest may be similar to that of finding a rotting animal carcass. The similarity of these experiences can also be seen in the language we use, as we tend to describe acts we think are immoral as gross, repulsive, or disgusting.

Despite these automatic evaluations, there may still be room for reasoning about morality. Based on evidence from fMRI scans while participants think about moral issues, Joshua Greene and colleagues have proposed a dual-process theory with two moral systems; one relying on emotional judgments and the other using rational, calculated judgments. Greene and colleagues found that when moral dilemmas were impersonal they engaged brain areas associated with rational consideration but when people were personally connected to a moral decision, they showed greater activation of their emotional system. These differing systems support the intuitive notion that we are better at rational analysis if we aren't personally involved in a moral decision.

Adolescence marks the transition from childhood to adulthood and thus is a time of great change. Physical changes during puberty are mostly associated with the development of reproductive ability. These changes can be categorized as primary sex characteristics, which are changes directly related to reproductive organs, and secondary sex characteristics which involve other areas of the body.

Boys begin puberty around age 12, with primary sex characteristics involving growth of the penis, testes, and related internal organs. Secondary sex characteristics in boys include the growth of facial hair, pubic hair, and underarm hair, as well as increased muscle growth and deepening of the voice. Around age 14, boys will experience spermarche (pronounced sperm-AR-key): their first ejaculation.

Puberty tends to begin earlier in girls, with onset around age 10. Primary sex characteristics are development of the genitals and ovaries, with the experience of menarche (pronounced men-AR-key), a girl's first menstrual cycle or period, occurring around age 12. Secondary sex characteristics include growth of pubic hair and underarm hair, as well as the development of breasts and widening of the hips.

In both boys and girls, puberty also marks the myelination of the frontal lobes of the brain, although this process won't be completed until around age 25. As we learned in the previous chapter, these brain regions are crucial for self-regulation and emotional control. Increased sexual drives without fully-developed capacities for self-regulation may be partially to blame for the increased impulsivity and risk-taking that are often associated with teenage behavior.

Piaget's formal operational stage began around puberty and this means that adolescents have new capacities for hypothetical thinking and abstract reasoning. These new abilities may be applied to teenagers' own lives, as they challenge existing beliefs and conventions. This may cause conflict with parents and other adults, though this conflict is often relatively minor and focused on things like clothing and hair styles, language and slang, or music preferences. Improvement in their cognitive abilities may also be related to the development of more efficient strategies for learning new information and solving problems, as well as improved memory capacity.

Lastly, adolescence is a time of socioemotional change. Adolescents find themselves with greater independence and their primary source of socialization shifts from parents and family to friends and peers. New social, romantic, and sexual experiences and opportunities abound and adolescents must figure out how they fit into this new social world (remember Erikson's identity vs. role confusion). They may try on multiple roles, eventually finding their own identity, which may also relate to group identities (such as “gamers”, “jocks”, etc.).

While psychoanalytic theorists focused on identification with a same-sex parent for learning sexual orientation, there's no evidence supporting this early view, and in fact no aspects of parenting have been strongly linked to sexual orientation. Parental sexual orientation doesn't seem to have an influence either, as children are just as likely to identify as homosexual whether they were raised by heterosexual or homosexual parents.

There does seem to be genetic influence on sexual orientation. One study of males found that for dizygotic twins, if one was gay the odds of the other being gay were 22%. For monozygotic twins, however, if one was gay the odds that the other was also gay were 52% (Bailey & Pillard, 1991). Of course, these odds still leave room for environment. Environmental influence during adolescence does not seem to dictate sexual orientation, in fact, in some cultures homosexual behaviors and rituals are a normal part of adolescence, and do not serve to “make” anyone gay in later life. More likely, the influence of environment on sexual orientation comes much earlier, before birth. There's some evidence that levels of prenatal hormones like testosterone may shape or perhaps even determine sexual orientation.

When it comes to the development of sexual orientation, there may also be differences between males and females. Most homosexual males report their first same-sex attraction some time around age 8 and also tend to report feeling that they have always been gay. Homosexual women, however, report less early certainty, supporting the notion that, in general, female sexuality may be more fluid or flexible (referred to as erotic plasticity) than male sexuality.

We should also remember that thinking of being gay, straight, or bisexual as an essential part of one's identity is a social construct. We should consider wider possibilities for cultural and individual variation in sexual identity, sexual behavior, and the meaning of same-sex relationships.

It's difficult to assess exactly when “adulthood” begins and this can vary rather widely in different cultures or time periods. In some cases, adulthood may seem to begin just as puberty ends, while in others there may be a long gap before one is considered to have arrived at adulthood. The challenges of adulthood include learning how to develop closeness and intimacy, managing new social and financial obligations, and learning how to care for children and aging parents.

Adulthood also brings physical changes, as physical abilities peak and then begin their gradual decline. Aging brings weight gain, loss of muscle mass, thinning and graying of hair, and decreases in sensory abilities for sight, smell, hearing, and taste.

Cognitive performance also tends to decline with age, though not all cognitive abilities are affected equally. While semantic memory does not show much decline, the ability to access and recall memories can be impaired. Fluid intelligence (for solving new problems) also slowly declines beginning in the early-to-mid twenties. This may seem surprisingly early but crystallized intelligence continues to improve, helping to compensate. Cognitive decline may be influenced by a number of other factors. Reduced effectiveness of other body systems such as kidney function or circulation may contribute, as well as changes in the ability to concentrate and reductions in novel mental stimulation.

More severe cognitive changes may arrive late in life, provided we live long enough to see them. Dementia (also known as senility) is a category of disorders which cause loss of mental function that is not a normal result of aging. Aging is still associated, however, as dementia affects only about 1% of those over age 65, but may affect as many as 25% of those over age 85. While most cognitive decline from dementia occurs gradually, some people experience more sudden and focused losses due to a series of mini-strokes in the brain (known as multiple-infarct dementia).

Alzheimer's disease is a specific type of dementia. Amyloid plaques (clusters of protein fragments between neurons) and neurofibrillary tangles (twisted protein strands inside neurons) accumulate, damaging or destroying cells. This loss of nerve cells can cause memory problems, disorientation, and difficulty speaking, swallowing, and walking. While some neuron loss in the hippocampus occurs with aging, patients with Alzheimer's disease experience more widespread damage to many areas, shrinking their brains dramatically. Some genetic risk factors have been identified, but there is not yet a clear cause of Alzheimer's disease nor is there is a cure or treatment for reversing damage.

While the cognitive and physical declines of aging cannot be stopped, they can be slowed, with physical exercise being a key strategy. Mental exercise and cognitive activity is likely also a factor, though as we saw in the chapter on intelligence, assessing the effectiveness of brain training is difficult and more research is needed.

Just as adolescents must adapt to a changing social world, adults also face social and emotional changes and transitions. The passionate love of early adulthood gradually gives way to more companionate love. Relationships change, physical and cognitive abilities diminish, and adults must confront the meaning of their lives. Though they tend to live longer than men (by about 5 years) women may be forced to reflect on some of their life choices a bit earlier at the onset of menopausemenopauseThe cessation of menstruation, typically in a woman's early 50s, marking the end of reproductive capacity.; which marks the end of their reproductive abilities.

By old age, the future is short, but generally bright. Elderly adults tend to be less concerned with acquiring new information and skills, and more concerned with emotional goals. The elderly tend to seek out positive emotional experiences, meaning that despite dealing with the many declines of aging, they tend to see an overall increase in well-being.