Objective 2| Describe the union of sperm and egg at conception. At conception, only one of the man’s sperm can penetrate the outer coating of the woman’s egg before the egg’s surface blocks out all others. Within about 12 hours, the nuclei of the sperm and egg fuse into a single cell.
Objective 3| Define zygote, embryo, and fetus, and explain how teratogens can affect development. Azygote is a fertilized egg, which becomes increasingly diverse. After about 10 days, the outer part of the cell mass attaches to the mother’s uterine wall and the inner cells soon become the embryo, beginning a stage of development when major organs form and begin to function. From 9 weeks after fertilization until birth, the organism, now known as a fetus, continues to develop and grow. Teratogens are potentially harmful agents that can pass through the placental screen and harm the developing embryo or fetus.
Objective 4| Describe some abilities of the newborn, and explain how researchers use habituation to assess infant sensory and cognitive abilities. Infants are born with a number of automatic responses (reflexes) that aid survival, including the rooting reflex that helps them locate food. Newborns’ rapidly developing senses of sight and hearing seem tuned to social events, such as a caretaker’s face or voice. Researchers can discover some of what preverbal infants sense and think by observing how they react to novel stimuli (such as colors, shapes, and forms) and grow bored with (habituate to) familiar stimuli. To recognize a new stimulus as different, an infant must remember the old stimulus, which indicates a simple form of learning.
Objective 5| Describe some developmental changes in a child’s brain, and explain why maturation accounts for many of our similarities. A newborn’s immature nervous system undergoes a rapid growth spurt after birth, as neural networks proliferate. Between ages 3 and 6, growth is most pronounced in the frontal lobes. Development in the association areas of the cortex enables thinking, memory, and language. Brain pathways continue to develop and strengthen with use until puberty, when pruning begins to eliminate excess connections. In the absence of severe abuse or neglect, maturation—the orderly sequence of genetically determined biological processes—guides all infants along the same general course of development.
Objective 6| Outline four events in the motor development sequence from birth to toddlerhood, and evaluate the effects of maturation and experience on that sequence. Though the timing may vary, almost all babies follow the same sequence of first rolling over, then sitting unsupported, then crawling, then walking. Experience has little influence; maturation, including that of the cerebellum, enables these events.
Objective 7| Explain why we have few memories of experiences during our first three years of life.“Infantile amnesia”—an inability to consciously recall events that happened before age 3—results from a change in the way the brain organizes memories at about that age. As the cortex matures, long-term storage increases; in addition, young children’s preverbal memories are not easily transformed into language.
Objective 12| Discuss the effects of nourishment, body contact, and familiarity on infant social attachment. Until the Harlows’ research in the mid-1950s, many psychologists believed that, through a conditioning process, children become attached (form an emotional tie) to those who provide nourishment. The Harlows’ experiments showed that infant monkeys would search out a non-nourishing “mother” that provided comfort in preference to one that provided nourishment without comfort. Ducks and other animals imprint, forming an attachment to a significant organism or object during a critical period (a time shortly after birth when proper development depends on exposure to certain stimuli or experiences).Humans do not imprint, but they do become attached to familiar people and things, which provide feelings of safety.
Objective 13| Contrast secure and insecure attachment, and discuss the roles of parents and infants in the development of attachment and an infant’s feelings of basic trust. In the experimental condition called the strange situation, researchers observe a mother and her child in a laboratory playroom, taking note of the child’s reactions as the mother leaves and reenters. Securely attached children play and explore comfortably in the mother’s presence, are distressed when she leaves, and seek contact when she returns. Insecurely attached children explore less in the mother’s presence and may cling to her, cry loudly when she leaves, and remain upset or act indifferent when she returns. Other studies show that sensitive responsive parents tend to have securely attached children. Genetically influenced temperament may evoke responsive parenting, but parental sensitivity has been taught and does increase infant attachment security to some extent. Father love as well as mother love is a predictor of children’s health and well-being. Adult relationships tend to reflect the secure or insecure attachment styles of early childhood, lending support to Erik Erikson’s idea that basic trust is formed in infancy by our experiences with responsive caregivers.
Objective 14| Assess the impact of parental neglect, family disruption, and day care on attachment patterns and development. When parental neglect or other trauma deprive children of the opportunity to form attachments, children become withdrawn and frightened and may not develop speech. If prolonged, childhood abuse places children at risk for a variety of physical, psychological, and social problems and may alter the brain’s production of serotonin. Damage from disruption of attachment bonds, as happens when children are placed in fostercare, appears to be minimal before 16 months of age. Children who are moved repeatedly or otherwise prevented from forming attachments by age 2, however, may be at risk for attachment problems. Quality day care, with responsive adults interacting with children in a safe and stimulating environment, does not appear to harm children’s thinking and language skills, but some studies have linked extensive time in daycare with increased aggressiveness and defiance.
Objective 15| Trace the onset and development of children’s self-concept. Self-concept, a sense of one’s identity and personal worth, emerges gradually, beginning at about 6 months. At 15 to 18months, children recognize themselves in a mirror. By school age, they can describe many of their own traits, and by age 8 to 10, their self-image is stable.
Objective 16| Describe three parenting styles, and offer three potential explanations for the link between authoritative parenting and social competence. Authoritarian parents impose rules and expect obedience. Permissive parents submit to children’s demands, ask little, and punish rarely.Authoritative parents are demanding but responsive to their children. Authoritative parenting correlates with social competence, but the cause-effect relationship is not clear. This style of parenting may produce socially competent children, or agreeable easygoing children may evoke authoritative parenting. Or a third factor, such as shared genes, may lead to a temperament that is comfortable with an authoritative parenting style and that manifests itself in agreeable easygoing social interactions.