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Human Development

The Big Picture: Chapter Overview

In psychology, development is defined as a pattern of change in human capabilities that begins at conception and continues throughout the life span. The growth involved in development is a product of physical processes, cognitive processes, and socioemotional processes. These three processes are related and influence each other. Some developmental psychologists argue that experiences during the first year or so of life create life long-lasting effects, while life-span developmentalists argue that experiences later in life are just as important as early life experiences.

Two concepts help explain the role of genetics in development: genotype and phenotype. The genotype is the actual genetic material, while the phenotype is the way the genotype is expressed in observable characteristics, such as physical attributes and psychological characteristics (e.g., intelligence). The nature-nurture issue involves the extent to which behavior and development are influenced by heredity (nature) and the environment (nurture). Developmentalists agree that the complex human psychology results from intricate combinations of nature and nurture influences. Optimal experiences or optimal life themes are what developmentalists argue allow certain humans to go beyond the framework set by their heredity and environmental influences.

The continuity view states that development involves gradual change, whereas the discontinuity view suggests that there are distinct developmental stages. The early-later experience issue centers on whether children are malleable throughout development and that later experiences are just as important as early experience.

Development can be organized into periods with approximate age ranges. Conception occurs when a sperm cell unites with an ovum. The fertilized egg is called a zygote. The first 2 weeks after conception are referred to as the germinal period; the period from 3 to 8 weeks is the embryonic period. The fetal period begins 2 months after conception and lasts about the next 7 months. Teratogens are agents that cause birth defects. Heroin and alcohol are examples of teratogens. A full-term infant is born 38 to 42 weeks following conception. Pre-term infants are at a higher risk for developmental problems and learning disorders than full-term babies. Massaging pre-term babies has been associated with weight gain, increased alertness, and improved performance in developmental tests.

Infants come into the world with a number of reflexes, including those associated with grasping, sucking, stepping, and startle. During the first 24 months of life, a human being develops at a faster pace than at any other point in the lifespan. At birth, the billions of neurons in the brain are scarcely connected, basically waiting for life's experiences to create the interconnections that will support future brain functioning and capacity. While the brain as a whole does not grow in size, the patterns and interconnections within it vary dramatically during infancy, childhood, and adolescence.

Piaget's theory of cognitive development focuses on how children actively construct their cognitive world and the stages that they go through. Children use schemas, which are cognitive frameworks that organize and interpret information. Two cognitive processes used by children are assimilation and accommodation. In the process of assimilation, the individual adjusts to new information by incorporating it into existing schemas; in accommodation, the individual adjusts to new information by modifying the existing schemas. Piaget believed that humans pass through four cognitive stages, each representing a different way of understanding the world: sensorimotor, preoperational, concrete operational, and formal operational.

Erik Erikson proposed an influential theory of development that focuses on psychosocial development. In each of the eight life-span stages in this theory, the individual is confronted with a crisis or challenge that must be resolved. The challenges of the four childhood stages are (1) trust versus mistrust, (2) autonomy versus shame, (3) initiative versus guilt, and (4) industry versus inferiority. According to Erikson, the more successfully the individual resolves each crisis, the more competent he or she is likely to become.

Developmental psychologists have been interested in studying the process of attachment, the close emotional bond between an infant and its caregiver. In a study of attachment in monkeys, Harlow and Zimmerman found that the comfort of contact is more important than feeding in the process of attachment. Lorenz described attachment in animals by using the process of imprinting. Some infants have more positive attachment experience than others. Ainsworth has described how attachment differs in the degree to which the caregiver is sensitive to the infant's signals. Children can also differ in temperament, which is an individual's behavioral style and characteristic way of responding. There are three basic types of temperament in children: easy child, difficult child, and slow-to-warm-up child. Parenting styles describe how parents interact with their children. According to Baumrind, there are four basic styles: authoritarian, authoritative, neglectful, and indulgent. Reciprocal socialization refers to the idea that children socialize parents just as parents socialize children. Divorce makes children more vulnerable to stress, aggressive behavior, and depression; however, the majority of children in divorced families adjust well.

Positive parenting involves spending time with children, emotion-coaching, and raising moral children. Kohlberg's theory suggests that moral development involves internalization, a change from behavior that is externally controlled to behavior that is controlled by internal, self-generated standards and principles. He also believed that moral development progresses through three levels: preconventional, conventional, and postconventional. Gilligan, emphasizing the role of gender on moral development, has suggested that Kohlberg's theory underrepresents the care perspective in moral development and overrepresents the justice perspective. Gender refers to the social and psychological aspects of being female and male. According to evolutionary psychology, differences in gender have resulted from gradual genetic adaptations, while alternative approaches, such as the social roles view of gender, argue that social experiences create gender differences. Social experiences can influence gender behavior through gender roles and gender schemas. Resilient children tend to have positive individual, family, and/or extrafamiliar factors that help them overcome obstacles faced in at risk circumstances, such as poverty and lack of quality parenting. Children in such at-risk circumstances benefit from programs that facilitate the factors contributing to resiliency, such as prevention and intervention programs, which give them an opportunity to become competent.

Adolescence is the developmental period between childhood and adulthood. While adolescence has long been characterized as a stage of developmental crisis, the majority of adolescents develop more positively that commonly believed. A significant physical event that occurs in adolescence is puberty. The hormones testosterone and estradiol reach high concentrations during puberty in boys and girls, respectively. According to Piaget, children between the ages of 11 and 15 develop the ability to think abstractly and logically and engage in hypothetical-deductive reasoning. Piaget called this stage formal operational thought. Adolescents experience a type of egocentrism characterized by the belief that they are unique, invincible, and the center of everyone's attention. During adolescence, individuals are developing their sense of identity, according to Erikson's stage of identity versus identity confusion. The search for identity can lead to adolescents wanting to gain independence from their parents, but at the same time fearing making the wrong decisions. Exploration and commitment are two dimensions of identity. Developing an ethnic identity is an important process during adolescence, particularly for the youth of ethnic minority groups. Adolescents experiencing at-risk situations such as delinquency, substance abuse, unprotected sex, adolescent pregnancy, and school-related problems are less likely to become productive adults. Successful programs for at-risk youths include providing individual attention and broad community-wide interventions.

The peak of our physical skills and health comes in early adulthood; however, this tends to be the life span period when people tend to engage in damaging life styles such as increased smoking, drinking, and poor eating habits. During middle adulthood, when the signs of aging start becoming more evident, a concern with health and youthful appearance tends to emerge. The majority of women do not experience psychological or physical problems from menopause. Life span refers to the upper boundary of a species' life, which is believed to be 120 years for humans. Life expectancy is the number of years that will probably be lived by the average person born in a particular year; a person born today in the United States is expected to live 77 years. In explaining aging, the cellular clock theory suggests that the upper limit of the human life span can be determined based on the number of times human cells can divide. The free-radical theory states that people age because free radicals inside their cells damage DNA and other cellular structures, leading to disorders such as cancer and arthritis. Health in late adulthood can be enhanced with exercise and a sense of self-control. Alzheimer's disease is characterized by progressive, irreversible brain disorders that involve gradual deterioration of memory, reasoning, language, and physical functioning.

During early adulthood, intellectual skills and fluid intelligence are strong. Later, during the middle adulthood years, crystallized intelligence increases and fluid intelligence decreases. Developmental psychologists use cross-sectional and longitudinal studies to research changes in cognitive development and the development of other psychological aspects. Although older adults show decline in the speed of processing information, they tend to outperform younger adults in general knowledge and wisdom. Socioemotional development in adulthood is concerned with such issues as work, intimacy, and lifestyle choices. During midlife, many individuals reach the highest satisfaction in their careers. Successful marriages are characterized by the following principles: feelings of fondness and admiration for each other, having each other as friends, giving up some power, and solving problems together. According to Levinson, while experiencing a midlife crisis, a person is concerned with being old, constructive, attached, and being masculine or feminine; however, the majority of adults do not experience a negative midlife crisis. Research in the development of adulthood and aging is increasingly demonstrating that while there are declines in physical, cognitive, and socioemotional functioning, overall older adults can have a positive and productive psychology.

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