|Psychology, 5/e Wortman, Loftus & Weaver|
|Online Learning Center
Developmental psychology is the branch of psychology that studies the progressive changes in human traits and abilities that occur throughout the life span. Psychologists approach human development from three perspectives: physical development, cognitive development, and social and personality development. Physical development includes all physiological changes that take place during the life span. Perhaps the most dramatic changes occur during puberty. Cognitive development is the changes associated with the "thinking" components of behavior. Language acquisition is an aspect of cognitive development that has received considerable attention. Social development is concerned with how people learn to interact with others and their environment. Personality development is concerned with the emergence of distinctive styles of thought, social interaction, and emotion.
Development is best understood as a process. Developmental processes are cumulative: present change builds on previous development. The concept of sequence emphasizes that development occurs in broadly predictable patterns. Any developmental event is the product of heredity and environment. Heredity refers to the inherited set of developmental instructions transmitted to us from our parents by our genes. Environment includes the external surroundings, social and cultural influences, and internal biological factors. Behavioral genetics is the field of study that tries to determine the relative contribution of environmental and hereditary differences to human thought and behavior. The interaction of heredity and environment can be visualized as a set of paths for development. In the early stages of life, development is more heavily influenced by heredity. As the life span lengthens, the number of possible paths increases. The influence of the environment on development in the later stages of life increases. A different pattern is present at the individual level. At birth, the number of paths for development is large. As the life span lengthens, the number of possible developmental paths decreases.
Human development may contain critical periods. If certain experiences do not occur during these periods, certain types of learning will not occur. For example, language acquisition is more heavily influenced by environmental factors during early childhood than during later childhood. There are profound psychological differences between adults and children. Understanding of the aspects of the psychological development that account for these differences has been shaped by three individuals: Freud, Watson, and Piaget.
Until the twentieth century, children were thought of as smaller adults. Freud was one of the first to perceive childhood as a period marked by important personal and developmental milestones. John B. Watson accepted Freud's notion that experience is cumulative. In the famous experiment with "Little Albert," Watson demonstrated that a phobia (fear of an object) could be learned. This experiment showed how early childhood experiences could influence later adult behavior.
Piaget was a successful biologist. He became curious about whether the adaptation he had witnessed in animals would be possible in humans. While administering intelligence tests to children, Piaget found that older children seemed to have changed their thought processes to better deal with test questions. Piaget proposed that children progressed through different "stages" of cognitive development. Eventually he devised a comprehensive theory of cognitive development.
Although newborns seem totally dependent on their environment, they are actually capable of a rather impressive set of skills. For example, they can see objects at close range, even though their vision is about 20/300. From birth, they show a preference for novel stimuli, and they will imitate an adult facial expression. Babies are able to differentiate similar sounds such as "b" and "p," can distinguish among smells, and can coordinate their auditory and visual processes. Research on the sensory capabilities of newborns generally involves the repeated presentation of one stimulus, then a shift to a new stimulus. Results show that a baby becomes less interested in the repeated stimulus, a kind of learning called habituation, but regains interest when the new stimulus is presented.
Newborns are equipped with several crucial reflexes. The rooting reflex, in which a baby turns its head toward anything that touches its cheek, allows the baby to locate a nipple for feeding. At this point, the sucking reflex takes over. When an object is placed in the infant's mouth, it automatically begins sucking. The grasping reflex, in which the newborn will firmly grasp an object placed in its hand, may be a remnant from our evolutionary past. The Moro reflex is a startle response that occurs in reaction to an intense movement or noise. The Babinski reflex is a response to stroking on the bottom of the foot. When the foot is stroked, the toes fan outward. These reflexes usually disappear by four months of age, and immature reflexes or reflexes which last too long can be signs of neurological problems.
Several changes in the brain allow this development: dendrites grow, many new synapses form, and myelin sheaths develop to help speed neural conduction. Also, the volume of nerve cell bodies increases and more glial cells grow, thereby tripling the size of the brain cortex from birth to four years of age.
Newborns are capable of learning from birth. Experimental observation leads one to believe that infants derive pleasure from solving problems. Research indicates that infants can remember over longer periods of time than was previously thought. However, adults have great difficulty in remembering events from their own infancy, a phenomenon called childhood amnesia. Several theories have been advanced to explain this memory failure. Freud believed we store these memories but cannot retrieve them in adulthood because of their sexual nature. Other researchers believe our retrieval failure results from our lack of appropriate retrieval cues or from the fact that early memories are not processed with language and are therefore not stored. Others think that brain changes that accompany growth disrupt these early memories.
Piaget proposed the most influential stage (qualitative) theory of cognitive development. He believed that intellectual development progresses through four major stages: the sensorimotor period (birth to two years), the preoperational period (the preschool years), the concrete-operational period (the elementary school years), and the formal-operational period (adolescence through adulthood). Three processes interact to advance the individual from one stage to another. Assimilation occurs when new information is incorporated into preexisting schemas. Accommodation is the process of changing thinking to adapt to new information. Information and schemas must be in a state of balance, called equilibration. Accommodation and equilibration move the individual from one stage to the next.
The information-processing approach argues that development is the increasing of the capacity to process information. This view describes the quantitative rather than the qualitative difference from one age to another. Whereas Piaget's qualitative differences imply that children of different ages perceive the world in quite different ways, information-processing theory suggests that children's thinking gradually improves.
According to Piaget, during the sensorimotor period, infants learn to act in the world but they do not appear to be able to think about their behavior until they develop the understanding that objects exist apart from their experience. Early in this period, infants do not understand that objects and people have a permanent existence. Instead they act as if objects cease to exist when the objects are removed from their presence. The development of object permanence is gradual: at four months a baby will reach for a partially hidden object; between four and eight months, it will visually track an object being placed behind a screen; between 8 and 12 months, it will search for a hidden object. Only in the last period of the sensorimotor stage will a baby follow the placement of an object from one location to another. Not all psychologists agree with Piaget's explanation. Some prefer to consider the development of object permanence as the result of improving memory capabilities. Research has demonstrated that the concept of object permanence may develop at earlier ages than Piaget has concluded.
The preschool years (the preoperational period) are most importantly characterized by representational thought, the ability to think about objects not immediately present. A preschooler's thought differs from an older child's in that it is egocentric (the child is unable to understand a situation from another person's perspective).
Older children (concrete-operational stage) can think in logical ways that preschoolers cannot and can perform concrete operations, or mental transformations. During this stage they learn conservation, the ability to recognize that certain features of things remain unchanged even when other features change. Piaget suggested that this learning reflects a qualitative change in cognition, but more recent work which shows that even young children can conserve numbers, if verbal instructions do not confuse them, challenges this view. Work by Rochel Gelman suggests that a child's inability to interpret the task may confuse the kinds of responses being given to the conservation problem.
Robbie Case has proposed a theory that integrates Piaget's perspective and the information-processing perspective. Case argues that as age increases, the efficiency of use of short-term memory storage space (the memory capacity available to think about problems) also increases. Movement from one stage to another requires the acquisition of new executive control structures (the child's current ways of representing the world and strategies for problem-solving). Executive controls can advance in one area before others depending on how efficient storage space is and how complex the new control structure is.
All normal children go through a series of stages in the development of spoken language, regardless of their culture. There are, however, individual variations in the rate of progress through the stages. From the earliest weeks of life, newborns develop distinguishable patterns of crying. By the age of three months they can coo; by six or seven months they can babble. Babbling does not seem to be directly related to adult speech, because it can contain sounds from all languages and because there are no differences between normal and deaf babies in the way they babble. Intonation (pitch pattern) and gesturing are also important in prespeech communication.
Children speak their first words at about the end of their first year. These words all focus on present objects and events. At this stage, children often commit errors of overextension (applying a category label to objects that do not fit the category, such as calling all four-legged animals doggie) and underextension (failing to include all category members in the category label, such as not calling a German shepherd a doggie). Through the processes of overextension and underextension, a child learns the mental representations used in a language.
Around age two, children begin putting words together in sentences, the first being two-word combinations. This telegraphic speech is characterized by elimination of descriptors and connectors; it focuses on nouns and action verbs. Even this early speech is highly structured. The emergence of this early speech depends on the attainment of a certain level of neurological maturation, particularly in the rapid increase in the number of neural synapses that occurs at about age one-and-one-half.
Between ages two and five, vocabulary increases dramatically, complex grammatical rules are mastered, and a child's ability to communicate moves beyond the immediate situation. Grammatical rules are acquired in sequential steps. Young children often commit errors of overregularization, in which they extend rules to instances in which the rules do not apply. Children also begin to learn about pragmatics, the study of how social context influences the use of language. Learning theories emphasize the crucial element of experience, and point out that no child learns language without exposure to language. Skinner argued that language mastery is a complex behavior, but a behavior nonetheless. Acquisition of language is accomplished through reinforcements and punishments.
Nativism is a theory of language acquisition that claims that language development is controlled by genetically programmed neural circuits. Noam Chomsky, for example, argued that the human brain contains a language acquisition device (LAD) which automatically analyzes the components of speech a child hears. The patterns of acquiring negation, the age of language mastery, and the speed of acquisition are similar enough across languages to support the nativist view.
Although most parents believe that their children learn language through imitation and reinforcement, research indicates that parents reinforce meaning rather than grammar. Consequently, most psychologists believe that language acquisition is highly creative, although reinforcement and imitation probably have some effect. Children are constantly talking, sometimes to no one in particular. This practice contributes to the mastery of language. It appears that language is to some degree innately human. Enhanced verbal abilities seem to be influenced by learning.
Younger children use fewer deliberate strategies for memory storage and retrieval than do older children. However, when required to use memory cues, younger children can utilize a strategy, thereby indicating that better memory may be the result of learning more efficient storage and retrieval strategies. Also, familiarity with material being remembered improves recall, and older children's better memories may be partially the result of being more familiar with the material being stored.
Preschoolers tend to overestimate their abilities to remember. Metacognition (the ability to monitor one's own thoughts) emerges in middle childhood, giving older children a much more realistic appraisal of their capabilities.
Formal operational intelligence expands a child's cognitive abilities to include systematic (scientific) testing of hypotheses, and hypothetical and abstract thinking. Piaget suggested that the formal operations stage developed at adolescence, although not all adolescents and adults use this ability all of the time. In fact, research has shown that many adults may be capable of formal thinking only in their areas of expertise. Information-processing theorists believe that the improvement in logical and hypothetical thinking which accompanies adolescence is the result of their having acquired better information-processing skills, such as better memory storage, retrieval strategies, and metacognition.
Formal operations was the most advanced type of thinking in Piaget's model. Klaus Riegel maintains that there is another stage called the dialectic operations stage. This stage involves debating deep moral, religious, or philosophical issues. Cognitive development does not stop at adolescence. Early adulthood (age 20 to 40) is a time of peak intellectual accomplishment, especially on tasks involving memory, speed, or intellectual flexibility. Middle adulthood (age 40 to 60) is accompanied by even better verbal skills and reasoning ability as well as increases in IQ. Only on tasks involving hand-eye coordination do middle adults perform less well than when they were younger. Although aging does produce some decline in long-term memory functions, the decline is usually small and probably is related to slower processing speeds. Short-term memory is unaffected. Of course, the effects of aging vary a great deal from person to person and result from both biological (hereditary) and environmental factors.
Human language is one of the most impressive cognitive abilities in humans. The debate between "environmentalists" and "nativist" views of language acquisition is of tremendous significance. Skinner published Verbal Behavior in 1957 in which he proposed the mechanisms by which language is learned are not fundamentally different from those by which animals learn behaviors. Skinner argued that verbal responses are shaped like all other responses. This point of view is known as the "learning" or "environmental" view.
A linguist named Noam Chomsky proposed an alternate framework based on the idea that human language abilities are innate. Chomsky argued that humans are "predisposed" to learn language. This framework is known as the "nativist" position. Eric Lenneberg, a psycholinguist, later modified Chomsky's ideas. Lenneberg argued that language abilities were innate, but that there were certain critical periods in which language must be acquired, or it will never be learned.
In 1970, social workers in Los Angeles became aware of a thirteen-year-old girl known as "Genie" who had been neglected and abused. Genie had been spent almost her entire life isolated in a closet. She was physically and cognitively impaired. A team of researchers began working with Genie to help her recover from her abuse. It was still unclear if she could be taught to acquire and use language. While Genie was able to acquire words for objects, her progress in rules of language slowed. After years of intensive study, researchers concluded that Genie's linguistic abilities were irreversibly restricted.
While it appeared that Genie's case supported Lenneberg's hypothesis of critical periods, many began to question the validity of such a conclusion. Genie may have been cognitively impaired from birth. In addition, the years of abuse must have had a negative impact on her neurological functioning. Genie's case, while being tragic, does not solve the debate between the "environmental" and "nativist" views on language acquisition.
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