Developmental psychology

Jean-Jacques Rousseau and John B. Watson are typically cited as providing the foundation for modern developmental psychology. In the mid-18th century, Jean Jacques Rousseau described three stages of development: infants (infancy), puer (childhood) and adolescence in Emile: Or, On Education. Rousseau's ideas were adopted and supported by educators at the time. Developmental psychology generally focuses on how and why certain changes (cognitive, social, intellectual, personality) occur over time in the course of a human life. Many theorists have made a profound contribution to this area of psychology. One of them is the psychologist Erik Erikson, who created a model of eight phases of psychosocial development. According to his theory, people go through different phases in their lives, each of which has its own developmental crisis that shapes a person's personality and behavior. In the late 19th century, psychologists familiar with the evolutionary theory of Darwin began seeking an evolutionary description of psychological development; prominent here was the pioneering psychologist G. Stanley Hall, who attempted to correlate ages of childhood with previous ages of humanity. James Mark Baldwin, who wrote essays on topics that included Imitation: A Chapter in the Natural History of Consciousness and Mental Development in the Child and the Race: Methods and Processes, was significantly involved in the theory of developmental psychology. Sigmund Freud, whose concepts were developmental, significantly affected public perceptions. ==Theories==

Psychosexual development Sigmund Freud developed a theory that suggested that humans behave as they do because they are constantly seeking pleasure. This process of seeking pleasure changes through stages because people evolve. Each period of seeking pleasure that a person experiences is represented by a stage of psychosexual development. These stages symbolize the process of becoming a mature adult. The first is the oral stage, which begins at birth and ends around a year and a half of age. During the oral stage, the child finds pleasure in behaviors like sucking and other mouth-related activities. The second is the anal stage, from about a year or a year and a half to three years of age. During the anal stage, the child defecates from the anus and is often fascinated with defecation. This period of development often occurs during toilet training. The child becomes interested in feces and urine. Children begin to see themselves as independent from their parents. They begin to desire assertiveness and autonomy. The third is the phallic stage, which occurs from ages 3 to 5 (most of a person's personality forms by this age). During the phallic stage, the child becomes aware of its sexual organs. Pleasure comes from finding acceptance and love from the opposite sex. The fourth is the latency stage, which occurs from age five until puberty. During the latency stage, the child's sexual interests are repressed. Stage five is the genital stage, which occurs from puberty through adulthood. During the genital stage, puberty begins. Children have now matured and begin to think about other people instead of just themselves. Pleasure comes from feelings of affection from other people. Freud believed there is tension between the conscious and the unconscious because the conscious resists what the unconscious seeks to express. To explain this, he developed three personality structures: id, ego, and superego. The id, the most primitive of the three, functions according to the pleasure principle: seek pleasure and avoid pain. The superego plays the critical and moralizing role, while the ego is the organized, realistic part that mediates between the desires of the id and the superego. Theories of cognitive development Jean Piaget, a Swiss theorist, posited that children learn by actively constructing knowledge through their interactions with their physical and social environments. He suggested that the adult's role in helping the child learn was to provide appropriate materials. In his interviews with children, which formed an empirical basis for his theories, he used a form of Socratic questioning to elicit their thinking. He argued that a principal source of development was through the child's inevitable generation of contradictions through their interactions with their physical and social worlds. The child's resolution of these contradictions led to more integrated and advanced forms of interaction, a developmental process that he called "equilibration." Piaget argued that intellectual development occurs through a series of stages generated by the process of equilibration. Each stage consists of steps that the child must master before moving on to the next. He believed that these stages are not separate from one another, but rather that each stage builds on the previous one in a continuous learning process. He proposed four stages: sensorimotor, pre-operational, concrete operational, and formal operational. Though he did not believe these stages occurred at any given age, many studies have determined when these cognitive abilities should take place. Stages of moral development Piaget claimed that logic and morality develop through constructive stages. Expanding on Piaget's work, Lawrence Kohlberg determined that the process of moral development was principally concerned with justice, and that it continued throughout the individual's lifetime. He proposed three levels of moral reasoning: pre-conventional, conventional, and post-conventional. Pre-conventional moral reasoning is typical of children and is characterized by reasoning based on the rewards and punishments associated with different courses of action. Conventional moral reasoning occurs during late childhood and early adolescence and is characterized by rule-based reasoning grounded in societal conventions. Lastly, post-conventional moral reasoning is a stage during which the individual sees society's rules and conventions as relative and subjective, rather than as authoritative. Kohlberg used the Heinz Dilemma to apply to his stages of moral development. The Heinz Dilemma involves Heinz's wife dying from cancer and Heinz having the dilemma of saving his wife by stealing a drug. Preconventional morality, conventional morality, and post-conventional morality apply to Heinz's situation. Recent scholarship challenges the "deficit models" of Piaget and Kohlberg, which portrayed humans as arriving amoral. Instead, research suggests infants possess innate "pre-moral" capacities and biological substrates for ethics. This perspective argues that children have cognitive equipment naturally receptive to divine attributes, such as immortality and omniscience, suggesting an innate orientation toward sensing transcendence. Stages of psychosocial development German-American psychologist Erik Erikson and his collaborator and wife, Joan Erikson, posit eight stages of human development, influenced by biological, psychological, and social factors, throughout the lifespan. Stages based on the model of hierarchical complexity Michael Commons enhanced and simplified Bärbel Inhelder and Piaget's developmental theory, and offers a standard method of examining the universal pattern of development. The Model of Hierarchical Complexity (MHC) is not based on the assessment of domain-specific information. It divides the Order of Hierarchical Complexity of tasks to be addressed from the Stage performance on those tasks. A stage is the order of hierarchical complexity of the tasks the participant successfully addresses. He expanded Piaget's original eight stages (counting the half-stages) to seventeen stages. The stages are: • Calculatory • Automatic • Sensory & Motor • Circular sensory-motor • Sensory-motor • Nominal • Sentential • Preoperational • Primary • Concrete • Abstract • Formal • Systematic • Metasystematic • Paradigmatic • Cross-paradigmatic • Meta-Cross-paradigmatic The hierarchical complexity order of tasks predicts performance difficulty, with an R ranging from 0.9 to 0.98. In the MHC there are three main axioms for an order to meet for the higher order task to coordinate the next lower order task. Axioms are rules used to determine how the MHC orders actions to form a hierarchy. These axioms are: a) defined in terms of tasks at the next lower order of hierarchical complexity task action; b) defined as the higher order task action that organizes two or more less complex actions; that is, the more complex action specifies the way in which the less complex actions combine; c) defined as the lower order task actions have to be carried out non-arbitrarily. Ecological systems theory Ecological systems theory, originally formulated by Urie Bronfenbrenner, specifies four types of nested environmental systems, with bidirectional influences within and between them. The four systems are microsystem, mesosystem, exosystem, and macrosystem. Each system contains roles, norms, and rules that can powerfully shape development. The microsystem is the direct environment in our lives, such as our home and school. Mesosystem is how relationships connect to the microsystem. The exosystem is a larger social system in which the child plays no role. Macrosystem refers to the cultural values, customs, and laws of society. The microsystem is the immediate environment surrounding and influencing the individual (e.g., school or home). The mesosystem is the combination of two microsystems and the ways they influence each other (e.g., sibling relationships at home vs. peer relationships at school). The exosystem is the interaction among two or more settings that are indirectly linked (for example, a father's job requiring more overtime influences his daughter's performance in school because he can no longer help with her homework). The macrosystem is broader, encompassing socioeconomic status, culture, beliefs, customs, and morals (for example, a child from a wealthier family may see a peer from a less wealthy family as inferior for that reason). Lastly, the chronosystem refers to the chronological nature of life events and how they interact and change the individual and their circumstances through transition (example: a mother losing her own mother to illness and no longer having that support in her life). has had widespread influence on the way psychologists and others approach the study of human beings and their environments. As a result of this conceptualization of development, these environments—from the family to economic and political structures—have come to be viewed as part of the life course from childhood through to adulthood. Developmental psychology of religion Modern research addresses a "contemporary paradox": institutional religious participation among youth is declining, yet spiritual seeking and belief in God remain high. Some theorists propose "spiritual transcendence" as a sixth personality factor beyond the Big Five, arguing it is a fundamental dimension of human nature rather than a derivative of other traits. This field explores how attachment styles influence an individual's "God concepts" and how adolescent biological maturation can influence religious devotion through psychoanalytic sublimation. Zone of proximal development Lev Vygotsky was a Russian theorist from the Soviet era, who posited that children learn through hands-on experience and social interactions with members of their culture. Vygotsky believed that a child's development should be examined during problem-solving activities. Unlike Piaget, he claimed that timely and sensitive intervention by adults when a child is on the edge of learning a new task (called the "zone of proximal development") could help children learn new tasks. The zone of proximal development is a concept used to explain children's learning and collaborative problem-solving with an adult or peer. Vygotsky was strongly focused on the role of culture in determining the child's pattern of development, arguing that development moves from the social level to the individual level. He felt that if scholars continued to disregard this connection, then this disregard would inhibit the full comprehension of the human consciousness. Jean Piaget, a Swiss developmental psychologist, proposed that learning is an active process because children learn through experience, make mistakes, and solve problems. Piaget proposed that learning should be holistic by helping students understand that meaning is constructed. Evolutionary developmental psychology Evolutionary developmental psychology is a research paradigm that applies the basic principles of Darwinian evolution, particularly natural selection, to understand the development of human behavior and cognition. It involves the study of both the genetic and environmental mechanisms that underlie the development of social and cognitive competencies, as well as the epigenetic (gene-environment interactions) processes that adapt these competencies to local conditions. EDP considers both the reliably developing, species-typical features of ontogeny (developmental adaptations) and individual differences in behavior from an evolutionary perspective. While evolutionary views tend to regard most individual differences as the result of either random genetic noise (evolutionary byproducts) and/or idiosyncrasies (for example, peer groups, education, neighborhoods, and chance encounters) rather than products of natural selection, EDP asserts that natural selection can favor the emergence of individual differences via "adaptive developmental plasticity". From this perspective, human development follows alternative life-history strategies in response to environmental variability, rather than following one species-typical pattern of development. Attachment theory Attachment theory, originally developed by John Bowlby, focuses on the importance of open, intimate, emotionally meaningful relationships. Attachment is described as a biological system or powerful survival impulse that evolved to ensure the survival of the infant. A threatened or stressed child will move toward caregivers who provide a sense of physical, emotional, and psychological safety. Attachment feeds on body contact and familiarity. Psychologist Harry Harlow's research with infant rhesus monkeys in the mid-20th century provided pivotal experimental support for attachment theory. His studies found that infant monkeys consistently preferred cloth surrogate mothers that provided comfort over wire ones that offered only food. These results demonstrated that emotional security and physical comfort are more critical to attachment than nourishment alone. Harlow's findings reinforced Bowlby's view that early caregiving relationships are biologically essential for healthy emotional development and social bonding later in life. Later, Mary Ainsworth developed the strange situation protocol and the concept of the secure base. This tool has been found to help understand attachment, such as the Strange Situation Test and the Adult Attachment Interview. Both of which help determine factors of certain attachment styles. The Strange Situation Test helps identify "disturbances in attachment" and whether specific attributes contribute to a particular attachment issue. The Adult Attachment Interview is a tool that is similar to the Strange Situation Test but instead focuses attachment issues found in adults. secure, anxious-avoidant, anxious-resistant,\ According to attachment theory, a psychological concept, people's capacity to develop healthy social and emotional ties later in life is greatly influenced by their early relationships with their primary caregivers, especially during infancy. This suggests that humans have an innate need to form strong bonds with caregivers to survive and remain healthy. Childhood attachment styles can have an impact on how people behave in adult social situations, including romantic partnerships. Nature vs nurture A significant concern of developmental psychology is the relationship between innateness and environmental influences on development. This is often referred to as "nature and nurture" or nativism versus empiricism. A nativist account of development would argue that the processes in question are innate, that is, they are specified by the organism's genes. What makes a person who they are? Is it their environment or their genetics? This is the debate of nature vs nurture. According to an empiricist viewpoint, those processes are learned through interaction with the environment. Today, most developmental psychologists take a more holistic approach, emphasizing the interaction between genetic and environmental influences. One of the ways this relationship has been explored in recent years is through the emerging field of evolutionary developmental psychology. The dispute over innateness has been well represented in the field of language acquisition studies. A major question in this area is whether or not certain properties of human language are specified genetically or can be acquired through learning. The empiricist position on language acquisition holds that language input provides the necessary information for learning language structure and that infants acquire language through a process of statistical learning. From this perspective, language can be acquired via general learning methods that also apply to other aspects of development, such as perceptual learning. The nativist position argues that the input from language is too impoverished for infants and children to acquire the structure of language. Linguist Noam Chomsky asserts that, evidenced by the lack of sufficient information in the language input, there is a universal grammar that applies to all human languages and is pre-specified. This has led to the idea that there is a special cognitive module suited for learning language, often called the language acquisition device. Chomsky's critique of the behaviorist model of language acquisition is regarded by many as a key turning point in the decline in the prominence of the theory of behaviorism generally. But Skinner's conception of "Verbal Behavior" has not died, perhaps in part because it has generated successful practical applications. Many researchers now emphasize that development results from a continuous, dynamic interaction between genetic predispositions and environmental influences. Rather than acting independently, nature and nurture are seen as intertwined forces, in which genetic factors can shape sensitivity to environmental inputs, and environmental conditions can influence gene expression throughout development. Continuity vs discontinuity One of the major discussions in developmental psychology includes whether development is discontinuous or continuous. Continuous development is quantifiable, whereas discontinuous development is qualitative. Quantitative estimates of development can include measuring a child's stature, memory, or attention span. "Particularly dramatic examples of qualitative changes are metamorphoses, such as the emergence of a caterpillar into a butterfly." Those psychologists who bolster the continuous view of improvement propose that improvement involves slow, progressive changes throughout life, with behavior in earlier stages of development laying the foundation for the abilities and capacities required for later stages. "To many, the concept of continuous, quantifiable measurement seems to be the essence of science". Stage theories of development rest on the suspicion that development may be a discontinuous process, comprising distinct stages characterized by subjective contrasts in behavior. They moreover assume that the structure of the stages is not variable from person to person; in any case, the time of each stage may vary. Stage theories can be differentiated with ceaseless hypotheses, which state that development is an incremental process. Stability vs change This issue concerns the extent to which one becomes an older version of their earlier self or develops into something different from who they were at an earlier stage of development. It considers the extent to which early experiences (especially infancy) or later experiences are the key determinants of a person's development. Stability is defined as the consistent ordering of individual differences with respect to some attribute. Change is altering someone/something. Most human development lifespan developmentalists recognize that extreme positions are unwise. Therefore, the key to a comprehensive understanding of development at any stage requires the interaction of different factors and not only one. Theory of mind Theory of mind is the ability to attribute mental states to ourselves and others. It is a complex but vital process in which children begin to understand the emotions, motives, and feelings of not only themselves but also others. Theory of mind allows individuals to understand that others have beliefs and desires that differ from their own. This ability enables successful social interactions by recognizing and interpreting others' mental states. If a child does not fully develop theory of mind within this crucial 5-year period, they can suffer from communication barriers that follow them into adolescence and adulthood. Exposure to more people and the availability of stimuli that encourage social-cognitive growth is a factor that relies heavily on family. ==Mathematical models==

Developmental psychology is concerned not only with describing the characteristics of psychological change over time but also with explaining the principles and internal workings underlying these changes. Psychologists have attempted to better understand these factors by using models. A model must account for the means by which a process takes place. This is sometimes done in reference to changes in the brain that may correspond to changes in behavior over the course of development. Mathematical modeling is useful in developmental psychology for implementing theory in a precise and easy-to-study manner, allowing generation, explanation, integration, and prediction of diverse phenomena. Several modeling techniques are applied to development: symbolic, connectionist (neural network), or dynamical systems models. Dynamic systems models illustrate how many different features of a complex system may interact to yield emergent behaviors and abilities. Nonlinear dynamics has been applied to human systems specifically to address issues that require attention to temporality, such as life transitions, human development, and behavioral or emotional change over time. Nonlinear dynamic systems is currently being explored as a way to explain discrete phenomena of human development such as affect, second language acquisition, and locomotion. ==Research areas==

Neural development One critical aspect of developmental psychology is the study of neural development, which examines how the brain changes across the lifespan. Neural development focuses on how the brain changes and develops during different stages of life. Studies have shown that the human brain undergoes rapid changes during the prenatal and early postnatal periods. These changes include the formation of neurons, the development of neural networks, and the establishment of synaptic connections. The formation of neurons and the establishment of basic neural circuits in the developing brain are crucial for laying the foundation of the brain's structure and function, and disruptions during this period can have long-term effects on cognitive and emotional development. Experiences and environmental factors play a crucial role in shaping neural development. Early sensory experiences, such as exposure to language and visual stimuli, can influence the development of neural pathways related to perception and language processing. Genetic factors play a huge role in neural development. Genetic factors can influence the timing and pattern of neural development, as well as the susceptibility to certain developmental disorders, such as autism spectrum disorder and attention-deficit/hyperactivity disorder. Research finds that the adolescent brain undergoes significant changes in neural connectivity and plasticity. During this period, a pruning process occurs in which certain neural connections are strengthened while others are eliminated, resulting in more efficient neural networks and increased cognitive abilities, such as decision-making and impulse control. The study of neural development provides crucial insights into the complex interplay between genetics, environment, and experiences in shaping the developing brain. By understanding the neural processes underlying developmental changes, researchers gain a clearer picture of human cognitive, emotional, and social development. Cognitive development Cognitive development is primarily concerned with how infants and children acquire, develop, and use internal mental capabilities such as problem-solving, memory, and language. Major topics in cognitive development include language acquisition and the development of perceptual and motor skills. Piaget was one of the influential early psychologists to study the development of cognitive abilities. His theory suggests that development proceeds through a set of stages from infancy to adulthood, with an endpoint or goal. Other accounts, such as that of Lev Vygotsky, have suggested that development does not progress through stages, but rather that the developmental process, which begins at birth and continues until death, is too complex for such structure and finality. Rather, from this viewpoint, developmental processes proceed more continuously. Thus, development should be analyzed rather than treated as a product to obtain. K. Warner Schaie has expanded the study of cognitive development into adulthood. Rather than being stable from adolescence, Schaie sees adults as progressing in the application of their cognitive abilities. Modern cognitive development has integrated the considerations of cognitive psychology and the psychology of individual differences into the interpretation and modeling of development. Specifically, the neo-Piagetian theories of cognitive development showed that the successive levels or stages of cognitive development are associated with increasing processing efficiency and working memory capacity. These increases explain differences between stages, progression to higher stages, and individual differences among children who are the same age and grade level. However, other theories have moved away from Piagetian stage theories. They are influenced by accounts of domain-specific information processing, which posit that development is guided by innate, evolutionarily specified, and content-specific information-processing mechanisms. Social and emotional development Developmental psychologists who are interested in social development examine how individuals develop social and emotional competencies. For example, they study how children form friendships, how they understand and deal with emotions, and how identity develops. Research in this area may involve studying the relationship between cognition, cognitive development, and social behavior. Emotional regulation (ER) refers to an individual's ability to modulate emotional responses across a variety of contexts. In young children, this modulation is in part controlled externally by parents and other authority figures. As children develop, they take on increasing responsibility for their internal state. Studies have shown that the development of ER is affected by the emotional regulation children observe in their parents and caregivers, the emotional climate at home, and the reactions of parents and caregivers to the child's emotions. Music also influences stimulating and enhancing the senses of a child through self-expression. A child's social and emotional development can be disrupted by motor coordination problems, as evidenced by the environmental stress hypothesis. The environmental hypothesis explains how children with coordination problems and developmental coordination disorder are exposed to several psychosocial consequences which act as secondary stressors, leading to an increase in internalizing symptoms such as depression and anxiety. Motor coordination problems affect fine and gross motor movement as well as perceptual-motor skills. Secondary stressors commonly identified include the tendency for children with poor motor skills to be less likely to participate in organized play with other children and more likely to feel socially isolated. Physical development Physical development concerns the physical maturation of an individual's body until it reaches adult stature. Although physical growth is a highly regular process, all children differ tremendously in the timing of their growth spurts. Studies are being done to analyze how the differences in these timings affect and are related to other variables of developmental psychology such as information processing speed. Traditional measures of physical maturity using X-rays are less commonly used nowadays than simple measurements of body parts such as height, weight, head circumference, and arm span. Neuroscientific research has contributed to understanding the biological mechanisms behind memory development. A study using diffusion MRI in children aged 4 to 12 found that greater maturity of white matter tracts, specifically the uncinate fasciculus and dorsal cingulum bundle, was associated with stronger episodic memory recall. These findings suggest that the structural development of white matter pathways plays a significant role in memory function during childhood. ==Research methods and designs==

Main research methods Developmental psychology employs many of the research methods used in other areas of psychology. However, infants and children cannot be tested in the same ways as adults, so different methods are often used to study their development. Developmental psychologists have many methods to study changes in individuals over time. Common research methods include systematic observation, such as naturalistic observation or structured observation; self-reports, such as clinical interviews or structured interviews; the clinical or case study method; and ethnography or participant observation. These methods differ in the extent of control researchers impose on study conditions, and how they construct ideas about which variables to study. Every developmental investigation can be characterized in terms of whether its underlying strategy involves the experimental, correlational, or case study approach. The experimental method involves "actual manipulation of various treatments, circumstances, or events to which the participant or subject is exposed; This method allows for strong inferences to be made of causal relationships between the manipulation of one or more independent variables and subsequent behavior, as measured by the dependent variable. Researchers may also observe how development varies among individuals and hypothesize about the causes of variation in their data. Longitudinal studies often require substantial time and funding, making them infeasible in some situations. Also, because members of a cohort all experience historical events unique to their generation, apparently normative developmental trends may, in fact, be universal only to their cohort. In a cross-sectional study a researcher observes differences among individuals of different ages at a single point in time. This generally requires fewer resources than the longitudinal method, and because the individuals come from different cohorts, shared historical events are less of a confounding factor. By the same token, however, cross-sectional research may not be the most effective way to study differences between participants, as these differences may result not from their different ages but from their exposure to different historical events. A third study design, the sequential design, combines both methodologies. Here, a researcher observes members of different birth cohorts at the same time, and then tracks all participants over time, charting changes in the groups. While much more resource-intensive, the format helps clarify the distinction between changes attributable to an individual or historical environment and those that are truly universal. Because every method has some weaknesses, developmental psychologists rarely rely on a single study or even a single method; instead, they seek consistent evidence from as many converging sources as possible. ==Life stages of psychological development==

Prenatal development Prenatal development is of interest to psychologists investigating the context of early psychological development. Prenatal development involves three main stages: the germinal stage, the embryonic stage, and the fetal stage. The germinal stage begins at conception and lasts until 2 weeks; the embryonic stage is the development from 2 weeks to 8 weeks; the fetal stage is from 9 weeks until birth. The senses develop in the womb itself: a fetus can both see and hear by the second trimester (13 to 24 weeks of age). The sense of touch develops in the embryonic stage (5 to 8 weeks). Most of the brain's billions of neurons are also developed by the second trimester. Babies are hence born with some odor, taste, and sound preferences, largely related to the mother's environment. Some primitive reflexes also arise before birth and remain present in newborns. One hypothesis is that these reflexes are vestigial and have limited use in early human life. Piaget's theory of cognitive development suggested that some early reflexes are building blocks for infant sensorimotor development. For example, the tonic neck reflex may help development by bringing objects into the infant's field of view. Other reflexes, such as the walking reflex, appear to be replaced by more sophisticated voluntary control later in infancy. This may be because the infant gains too much weight after birth to be strong enough to use the reflex, or because the reflex and subsequent development are functionally different. It has also been suggested that some reflexes (for example the moro and walking reflexes) are predominantly adaptations to life in the womb with little connection to early infant development. Several environmental agents—teratogens—can cause damage during the prenatal period. These include prescription and nonprescription drugs, illegal drugs, tobacco, alcohol, environmental pollutants, infectious disease agents such as the rubella virus and the toxoplasmosis parasite, maternal malnutrition, maternal emotional stress, and Rh factor blood incompatibility between mother and child. Many statistics prove the effects of the aforementioned substances. A leading example of this would be that at least 100,000 "cocaine babies" were born in the United States annually in the late 1980s. "Cocaine babies" are proven to have quite severe and lasting difficulties that persist throughout infancy and right throughout childhood. The drug also encourages behavioral problems in the affected children and defects of various vital organs. Infancy From birth until the first year, children are referred to as infants. As they grow, children respond to their environment in unique ways. Developmental psychologists vary widely in their assessment of infant psychology, and the influence the outside world has upon it. The majority of a newborn infant's time is spent sleeping. At first, their sleep cycles are evenly spread throughout the day and night, but after a couple of months, infants generally become diurnal. In human or rodent infants, there is always the observation of a diurnal cortisol rhythm, which is sometimes entrained with a maternal substance. Nevertheless, the circadian rhythm starts to take shape; a 24-hour rhythm is observed in just some few months after birth. • quiet waking, and active waking • fussing and crying. In a normal setup, infants cry for different reasons. Mostly, infants cry due to physical discomfort, hunger, or to receive attention or stimulation from their caregiver. Infant perception Infant perception is what a newborn can see, hear, smell, taste, and touch. These five features are considered the "five senses". Because of these different senses, infants respond to stimuli differently. This is evidenced by the primitive reflexes described above, and the relatively advanced development of the somatosensory cortex. • Pain: Infants feel pain similarly, if not more strongly than older children, but pain relief in infants has not received as much attention as an area of research. Glucose is known to relieve pain in newborns. Language Babies are born with the ability to discriminate virtually all sounds of all human languages. Infants of around six months can differentiate between phonemes in their own language, but not between similar phonemes in another language. Notably, infants can distinguish between different durations and sound levels and readily differentiate among the languages they have encountered, making it easier for them to understand a given language than for adults to do so. At this stage, infants also start to babble, making vowel-consonant sounds as they try to understand the true meaning of language and copy what they hear in their surroundings, producing their own phonemes. In various cultures, a distinct form of speech called "babytalk" is used when communicating with newborns and young children. This register consists of simplified terms for common topics such as family members, food, hygiene, and familiar animals. It also exhibits specific phonological patterns, such as substituting initial velar sounds for alveolar sounds, especially in languages like English. Furthermore, babytalk often involves morphological simplifications, such as regularizing verb conjugations (for instance, saying "corned" instead of "cornered" or "goed" instead of "went"). This language is typically taught to children and is perceived as their natural way of communication. Interestingly, in mythology and popular culture, certain characters, such as the "Hausa trickster" or the Warner Bros cartoon character "Tweety Pie", are portrayed as speaking in a babytalk-like manner. Infant cognition: the Piagetian era Piaget suggested that an infant's perception and understanding of the world depended on their motor development, which was required for the infant to link visual, tactile, and motor representations of objects. The concept of object permanence refers to the knowledge that an object exists even when it is not directly perceived or visible; in other words, something is still there even if it is not visible. This is a crucial developmental milestone for infants, who learn that something is not necessarily lost forever just because it is hidden. When a child displays object permanence, they will look for a hidden toy, showing that they are aware the item is still there even when covered by a blanket. Most babies begin to exhibit signs of object permanence around 8 months of age. According to this theory, infants develop object permanence through touching and handling objects. Discovery of new behaviors results from classical and operant conditioning, and the formation of habits. Other research has suggested that young infants in their first six months of life may possess an understanding of numerous aspects of the world around them, including: • an early numerical cognition, that is, an ability to represent number and even compute the outcomes of addition and subtraction operations; • an ability to infer the goals of people in their environment; • an ability to engage in simple causal reasoning. Critical periods of development There are critical periods in infancy and childhood during which the development of certain perceptual, sensorimotor, social, and language systems depends crucially on environmental stimulation. Feral children such as Genie, deprived of adequate stimulation, fail to acquire important skills and are unable to learn in later childhood. In this case, Genie is used to represent the case of a feral child because she was socially neglected and abused while she was just a young girl. She underwent abnormal child psychology, which involved problems with her linguistics. This happened because she was neglected while she was very young, with no one to care about her, and had less human contact. The concept of critical periods is also well established in neurophysiology, as demonstrated by the work of Hubel and Wiesel, among others. Neurophysiology in infants generally provides correlating details that exist between neurophysiological details and clinical features, and also focuses on vital information on rare and common neurological disorders that affect infants. Developmental delays Studies have examined differences between children with developmental delays and those with typical development. Normally, when comparing one another, mental age (MA) is not taken into consideration. There still may be differences in developmentally delayed (DD) children vs. typical development (TD) behavioral, emotional, and other mental disorders. Compared with MA children, there is a greater difference in overall normal developmental behaviors. DDs can cause lower MA, so comparing DDs with TDs may not be as accurate. Pairing DDs specifically with TD children at similar MA can be more accurate. There are levels of behavioral differences that are considered normal at certain ages. When evaluating DDs and MA in children, consider whether those with DDs have a larger amount of behavior that is not typical for their MA group. Developmental delays tend to contribute to other disorders or difficulties than their TD counterparts. Toddlerhood Infants shift between the ages of one and two to a developmental stage known as toddlerhood. In this stage, an infant's transition into toddlerhood is marked by self-awareness, linguistic development, and the emergence of memory and imagination. During toddlerhood, babies begin learning how to walk, talk, and make decisions for themselves. An important characteristic of this age period is the development of language, where children are learning how to communicate and express their emotions and desires through the use of vocal sounds, babbling, and eventually words. Self-control also begins to develop. At this age, children take the initiative to explore, experiment, and learn from making mistakes. Caretakers who encourage toddlers to try new things and test their limits, help the child become autonomous, self-reliant, and confident. If the caretaker is overprotective or disapproving of independent actions, the toddler may begin to doubt their abilities and feel ashamed of the desire for independence. The child's autonomic development is inhibited, leaving them less prepared to deal with the world in the future. Toddlers also begin to identify with gender roles, acting according to their perception of what a man or woman should do. Socially, the period of toddler-hood is commonly called the "terrible twos". Toddlers often use their new-found language abilities to voice their desires, but are often misunderstood by parents due to their language skills just beginning to develop. A person at this stage, testing their independence, is another reason behind the stage's infamous label. Tantrums in a fit of frustration are also common. Childhood Erik Erikson divides childhood into four stages, each with its distinct social crisis: :* Stage 1: Infancy (0 to 1½) in which the psychosocial crisis is Trust vs. Mistrust :* Stage 2: Early childhood (2½ to 3), in which the psychosocial crisis is Autonomy vs. Shame and doubt :* Stage 3: Play age (3 to 5) in which the psychosocial crisis is Initiative vs. Guilt. (This stage is also called the "pre-school age", "exploratory age", and "toy age".) :* Stage 4: School age (5 to 12), in which the psychosocial crisis is Industry vs. Inferiority Infancy As stated, Erikson's psychosocial crisis is Trust versus Mistrust. Needs are the foundation for gaining or losing trust in the infant. If the needs are met, trust in the guardian and the world forms. If the needs are not met or the infant is neglected, mistrust forms alongside feelings of anxiety and fear. Early Childhood Autonomy versus shame follows trust in infancy. The child begins to explore their world at this stage and develops preferences. If autonomy is allowed, the child grows in independence and their abilities. If freedom of exploration is hindered, it leads to feelings of shame and low self-esteem. Preoperational and then operational thinking develops, which means actions are reversible, and egocentric thought diminishes. Preschoolers' motor skills improve, allowing them to do more things for themselves. They become more independent. No longer completely dependent on others' care, this age group's world expands. More people have a role in shaping their individual personalities. Preschoolers explore and question their world. For Jean Piaget, the child is "a little scientist exploring and reflecting on these explorations to increase competence" and this is done in "a very independent way". Play is a major activity for ages 3–5. For Piaget, through play, "a child reaches higher levels of cognitive development." In their expanded world, children in the 3–5 age group attempt to find their own way. If this is done in a socially acceptable way, the child develops initiative. If not, the child develops guilt. Children who develop "guilt" rather than "initiative" have failed Erikson's psychosocial crisis for the 3–5 age group. Middle and Late childhood ages 6–12 According to Erik Erikson, the psychosocial crisis during middle childhood is Industry vs. Inferiority, which, if successfully met, instills a sense of Competence in the child. School offers an arena in which children can gain a view of themselves as "industrious (and worthy)". They are "graded for their school work and often for their industry". They can also develop industry outside of school in sports, games, and volunteer work. Children who achieve "success in school or games might develop a feeling of competence." The "peril during this period is that feelings of inadequacy and inferiority will develop. The Centers for Disease Control (CDC) divides Middle Childhood into two stages, 6–8 years and 9–11 years, and gives "developmental milestones for each stage". Middle Childhood (6–8) Entering elementary school, children in this age group begin to think about the future and their "place in the world". Working with other students and wanting their friendship and acceptance becomes more important. This leads to "more independence from parents and family". As students, they develop the mental and verbal skills "to describe experiences and talk about thoughts and feelings". They become less self-centered and show "more concern for others". Erik Erikson labels this stage identity versus role confusion. Erikson emphasizes the importance of developing a sense of identity in adolescence because it affects the individual throughout their life. Identity is a lifelong process, shaped by curiosity and active engagement. Role confusion is often considered the current state of an individual's identity. Identity exploration is the process of changing from role confusion to resolution. During Erik Erikson's identity versus role uncertainty stage, which occurs in adolescence, people struggle to form a cohesive sense of self while exploring many social roles and prospective life routes. This time is characterized by deep introspection, self-examination, and the pursuit of self-understanding. Adolescents are confronted with questions regarding their identity, beliefs, and future goals. The major problem is building a strong sense of identity in the face of society standards, peer pressure, and personal preferences. Adolescents engage in identity exploration, commitment, and synthesis, actively seeking new experiences, embracing ideals and aspirations, and integrating their evolving sense of self into a coherent identity. Successfully navigating this stage builds the groundwork for good psychological development in adulthood, allowing people to pursue meaningful relationships, make positive contributions to society, and handle life's adversities with perseverance and purpose. It is divided into three parts, namely: • Early Adolescence: 9 to 13 years • Mid Adolescence: 13 to 15 years and • Late Adolescence: 15 to 18 years The adolescent unconsciously explores questions such as "Who am I? Who do I want to be?" Like toddlers, adolescents must explore, test limits, become autonomous, and commit to an identity, or sense of self. Different roles, behaviors, and ideologies must be tried out to select an identity. Role confusion and inability to choose a vocation can result from a failure to achieve a sense of identity through, for example, friends. Early adulthood Early adulthood generally refers to the period between ages 18 and 39, and according to theorists such as Erik Erikson, is a stage where development is mainly focused on maintaining relationships. Erikson shows the importance of relationships by labeling this stage intimacy vs isolation. Intimacy suggests a process of becoming part of something larger than oneself through sacrifice in romantic relationships and by working toward both life and career goals. Other examples include creating bonds of intimacy, sustaining friendships, and starting a family. Some theorists argue that the development of intimacy skills depends on the resolution of earlier developmental stages. A sense of identity gained in the previous stages is also necessary for intimacy to develop. If this skill is not learned, the alternative is alienation, isolation, a fear of commitment, and the inability to depend on others. Isolation, on the other hand, suggests something different than most might expect. Erikson defined it as a delay in commitment to maintain freedom. Yet, this decision does not come without consequences. Erikson explained that choosing isolation may affect one's chances of getting married, progressing in a career, and overall development. Middle adulthood Middle adulthood generally refers to the period between ages 40 and 64. During this period, middle-aged adults experience a conflict between generativity and stagnation. Generativity is the sense of contributing to society, the next generation, or one's immediate community. On the other hand, stagnation results in a lack of purpose. The adult's identity continues to develop in middle-adulthood. Middle-aged adults often adopt opposite gender characteristics. The adult realizes they are halfway through their life and often reevaluates vocational and social roles. Life circumstances can also cause a reexamination of identity. Physically, middle-aged individuals experience declines in muscular strength, reaction time, sensory acuity, and cardiac output. Also, women experience menopause at an average age of 48.8 and a sharp drop in the hormone estrogen. Men experience an equivalent endocrine system event to menopause. Andropause in males is a hormone fluctuation with physical and psychological effects that can be similar to those seen in menopausal females. As men age, lowered testosterone levels can contribute to mood swings and a decline in sperm count. Sexual responsiveness can also be affected, including delays in erection and longer periods of penile stimulation required to achieve ejaculation. The important influence of biological and social changes experienced by women and men in middle adulthood is reflected in the fact that depression is highest at age 48.5 around the world. Old age The World Health Organization finds "no general agreement on the age at which a person becomes old." Most "developed countries" set the age as 65 or 70. However, in developing countries, the inability to make an "active contribution" to society, rather than chronological age, marks the beginning of old age. According to Erikson's stages of psychosocial development, old age is the stage in which individuals assess the quality of their lives. Erikson labels this stage as integrity versus despair. For integrated persons, there is a sense of fulfillment in life. They have become self-aware and optimistic through life's commitments and connections with others. While reflecting on life, people at this stage develop a sense of contentment with their experiences. If a person falls into despair, they are often disappointed about failures or missed chances in life. They may feel that the time left in life is an insufficient amount to turn things around. Physically, older people experience a decline in muscular strength, reaction time, stamina, hearing, distance perception, and the sense of smell. They also are more susceptible to diseases such as cancer and pneumonia due to a weakened immune system. Programs aimed at balance, muscle strength, and mobility have been shown to reduce disability among mildly (but not more severely) disabled elderly. Sexual expression depends in large part upon the emotional and physical health of the individual. Many older adults continue to be sexually active and satisfied with their sexual activity. Mental disintegration may also occur, leading to dementia or ailments such as Alzheimer's disease. The average age of onset for dementia in males is 78.8 and 81.9 for women. It is generally believed that crystallized intelligence increases up to old age, while fluid intelligence decreases with age. Whether or not normal intelligence increases or decreases with age depends on the measure and study. Longitudinal studies show that perceptual speed, inductive reasoning, and spatial orientation decline. An article on adult cognitive development reports that cross-sectional studies show that "some abilities remained stable into early old age". ==Parenting==

Parenting variables alone have typically accounted for 20 to 50 percent of the variance in child outcomes. All parents have their own parenting styles. Parenting styles, according to Kimberly Kopko, are "based upon two aspects of parenting behavior: control and warmth. Parental control refers to the degree to which parents manage their children's behavior. Parental warmth refers to the degree to which parents are accepting and responsive to their children's behavior." Parenting styles The following parenting styles have been described in the child development literature: • Authoritative parenting is characterized by parents who have high parental warmth, responsiveness, and demandingness, but rate low in negativity and conflict. These parents are assertive but not intrusive or overly restrictive. This method of parenting is associated with more positive social and academic outcomes. The beneficial outcomes of authoritative parenting are not necessarily universal. Among African American adolescents, authoritative parenting is not associated with academic achievement in the absence of peer support for achievement. • Authoritarian parenting is characterized by low levels of warmth and responsiveness with high levels of demandingness and firm control. • Rejecting or neglectful parenting is characterized by low levels of demandingness and responsiveness. These parents are usually unsupportive, unstructured, and uninterested in their children's lives. Low degrees of reactivity and demandingness are characteristics of this parenting style. In particular, a study in the U.S. and New Zealand found the presence of the natural father was the most significant factor in reducing rates of early sexual activity and rates of teenage pregnancy in girls. However, neither a mother nor a father is actually essential in successful parenting, and both single parents as well as homosexual couples can support positive child outcomes. Children need at least one consistently responsible adult with whom they can form a positive emotional bond. Having multiple such figures further increases the likelihood of positive outcomes. Divorce Another parental factor often debated in terms of its effects on child development is divorce. Divorce in itself is not a determining factor of negative child outcomes. In fact, the majority of children from divorcing families fall into the normal range on measures of psychological and cognitive functioning. Many mediating factors play a role in determining the effects divorce has on a child, for example, divorcing families with young children often face harsher consequences in terms of demographic, social, and economic changes than do families with older children. Positive coparenting after divorce is part of a pattern associated with positive child coping, while hostile parenting behaviors lead to a destructive pattern, leaving children at risk. Additionally, a direct parental relationship with the child also affects the development of a child after a divorce. Overall, protective factors that facilitate positive child development after a divorce include maternal warmth, a positive father-child relationship, and parental cooperation. == Cross-cultural ==

A way to improve developmental psychology is through cross-cultural studies. The field of psychology in general assumes that "basic" human developments are representative of any population, specifically the Western-Educated-Industrialized-Rich and Democratic (W.E.I.R.D.) subjects relied on for the majority of its studies. Previous research generalizes findings from W.E.I.R.D. samples because many in the Psychological field assume certain aspects of development are exempt from, or unaffected by, life experiences. However, many of the assumptions have been proven incorrect or are not supported by empirical research. For example, according to Kohlberg, moral reasoning is dependent on cognitive abilities. While both analytical and holistic cognitive systems can develop in any adult, the West remains on the analytical end of the spectrum. In contrast, the non-West tends to rely on holistic processes. Furthermore, moral reasoning in the West focuses on aspects that support autonomy and the individual. In contrast, non-Western adults emphasize moral behaviors that support the community and maintain an image of holiness or divinity. Not all aspects of human development are universal, and we can learn a lot from observing different regions and subjects. Indian model of human development An example of a non-Western model of development stages is the Indian model, which focuses much of its psychological research on morality and interpersonal progress. The developmental stages in Indian models are rooted in Hinduism, which primarily outlines stages of life in the process of someone discovering their fate or Dharma. This cross-cultural model can add another perspective to psychological development in which the West behavioral sciences have not emphasized kinship, ethnicity, or religion. It is within early and middle adulthood that we see moral development progress. Early, middle, and late adulthood are all concerned with caring for others and fulfilling Dharma. The main distinction between early adulthood and middle or late adulthood lies in the extent of their influence. Early adulthood emphasizes the importance of fulfilling the immediate family needs, until later adulthood, when they broaden their responsibilities to the general public. The old-age life stage development reaches renunciation or a complete understanding of Dharma. Current mainstream views in psychology are opposed to the Indian model of human development. The criticism of such models is that they promote an overly protective parenting style and encourage excessive dependence. It focuses on interpersonal instead of individual goals. Also, there are some overlaps and similarities between Erikson's stages of human development and the Indian model, but both of them still have major differences. The West prefers Erickson's ideas over the Indian model because scientific studies support them. Life cycles based on Hinduism are less favored because they are not supported by research and focus on ideal human development. ==See also==