Human development and bechavior

1. Human development and bechavior

2. The study of human development • The study of human development concerns the ways in which people change with the passage of time. It emphasizes a pattern of changes throughout the life span, often in three broad areas: physical, social, and cognitive. • We consider each of these areas and then an issue underlying all of them: the influences of heredity and environment.

3. Biological Influences • The behavior of these children was partly a function of their genetic endowment and, like all of us, each child began life in a very small way, as a single cell. This fertilized cell, resulting from the union of the father's sperm and the mother's egg, is but half the size of the dot over this "i," yet all of the inborn influences on our physical, mental, and even social development are set at this miraculous moment of conception. • As we leave these infants to consider the structures and processes behind all of our origins, we must realize that no further hereditary influences are possible during the rest of our lives. Our entire heredity, the sum of characteristics and potentialities biologically transmitted from our parents, is contained in this one fertilized cell.

4. Chromosomes and Genes • One pair consists of the sex chromosomes, X and Y, which result in the development of a male or female. The male is XY, receiving an X from the mother and a Ffrom the father, whereas the female receives an X from each parent. The two little girls each had an XX combination. • Within the chromosomes are even more fundamental determiners of heredity, called genes, which contain the basic blueprint that specifically directs the development of most physical characteristics and certain behavioral traits.

5. During prenatal life • During prenatal life, as the first cell successively multiplies, the complete genetic code is passed on to each of the resulting cells. • All cells in the human body thus contain the same inheritance with one exception, the reproductive cells.

6. The reproductive cells • Beginning in puberty, when the reproductive cells first appear, cell division occurs in such a way that the sperm in the male and the egg in the female receive only one member of each pair of chromosomes. • The chromosomes contain only one-half of the individual's full genetic code; furthermore, the different eggs or sperms produced by the same individual receive different sets of chromosomes with their countless thousands of genes.

7. Single-pair Traits • The physical features of the two orphan girls were determined by a particular assortment of genes. • Perhaps one of the girls had brown eyes and, since genes come in pairs, let us refer to these genes as BB. The capital В is used because the gene for brown eyes is a dominant gene, meaning that it takes precedence, suppressing the influence of its counterpart. The other child might have a Bb, and it would also be brown-eyed because of the dominant B. Still another child might have bb.

8. Multiple-pair Traits • It is speculated that multiple pairs of genes involve two degrees of expression but no dominance. One pair might be expressed as A and a, another as В and b, and so on for as many genes as are relevant. A rat with AA is brighter than aa, and a rat with Aa falls between the two. Similarly, BB is brighter than Bb which, in turn, is brighter than bb. • Since it is assumed that no dominance exists in the gene pairs, the brightest rat would be AABBCCDD, the dullest aabbccdd, and the intermediate levels would be AaBbCcDd, aAbbCCDd, and so forth.

9. Concept of Imprinting • Under normal circumstances, for example, newborn ducklings and goslings follow their mother soon after hatching, perhaps because they are stimulated initially by her movements or vocalizations. This learned attachment of young animals to members of their own species is called imprinting, and there is nothing extraordinary about this following behavior except that it is acquired during a certain optimal time for learning. • This period varies for different species, but in geese it occurs up to sixteen hours after birth, after which readiness to learn to follow declines rapidly. The young bird is so ready during this initial period that this following behavior can be elicited by almost any perceptible object that moves, living or inanimate.

12. Sensitive Periods • Many researchers believe that there is an important early period for human social responsiveness, but they do not speculate in regard to the exact interval. It is probably unwise to assume a critical period when there may be different periods for different responses. • The first three days after birth, for example, may be sufficient for initiating infant bonding to the mother's voice. Some investigators speak of a sensitive period, implying its importance but not its irreversibility.

13. Heredity and environment • The tests administered to the transferred children before their departure had been administered routinely to all the children in the orphanage. On this basis a useful research study could be designed. • It would be possible to identify a comparable nontransferred group, and for this purpose he selected 12 children with an average age of 17 months and an average IQ of 87. • The chief factor accounting for this difference, according to Skeels, was the amount of stimulation and adult-child interaction for the transferred children. Their rapid and positive physical, social, and cognitive changes suggested that environmental conditions can play a significant role in the developmental process.

14. Nature-Nurture Issue • Each of us is a product of both heredity and environment, but are two individuals different because of their heredity or because of their environment? • Sir Francis Galton called this question the nature-nurture issue, referring to the influences of heredity and environment, respectively, and he thereby called further attention to a long-standing controversy.

15. Studies with Animals • The most precise demonstrations of heredity-environment relationships are found in animal studies because here even the most basic environmental factors can be readily controlled. The development of swimming in tadpoles, flying in pigeons, and sexual behavior among monkeys all have been studied in this way. • Series of experiments with infant monkeys also showed that extreme environments can alter the potential influences of heredity. Monkeys that do not receive the usual maternal stimulation and affection during infancy fail to develop into normal adults. Their social relationships are infrequent or ineffective.

16. Identical Twins • At the human level nature has provided us with some help in assessing these influences. Heredity in fraternal twins is no more similar than between any other pair of siblings, but in identical twins heredity is exactly the same. • When these twins were brought together and compared, they were found to be much alike in physical characteristics and appearance. • Differences in educational opportunity can produce significant differences in intelligence. Finally, in personality traits the separately reared twins were sometimes similar and sometimes very different.

17. Twins in different age

18. Interaction Principle • Through such investigations it is now apparent that the heredity-environment question is not an either-or matter. The contributions of both factors are widely acknowledged, and the main focus of contemporary research is on discovering the ways in which they combine to bring about a given characteristic. • The current concern is with the relationships between these two sets of factors, an interplay of forces that can be extremely complex and intermixed

19. Concept of Readiness • Readiness is the time at which an organism is first physiologically capable of responding properly in a given situation. The degree of preparedness to act or respond to a particular stimulus. 2. The level of preparation for a given task sufficient to result in meaningful learning. • With different instructional opportunities, children are ready to learn two and three years earlier and, of course, later.

20. Readiness for school • Six and a half years was the average mental age of readiness for reading as it was then taught in the schools.

21. Individual differences • These differences might involve physical, social, cognitive, or other characteristics. • Psychologists sometimes study the ways in which people are alike, which can be part of developmental psychology, and sometimes they focus on the ways in which we differ, called the psychology of individual differences.

22. Developmental changes in the life span • The most rapid developmental changes in the life span take place in childhood. According to Erikson's theory, they concern the development of trust, autonomy, initiative, and industry. • If these issues are not resolved in the early years, they are difficult to resolve later.

23. Developmental changes in the life span • A second period of rapid development occurs during adolescence, when hormonal secretions produce physiological changes having repercussions for physical, social, emotional, and sexual life, as well as personality. • The most significant psychosocial issue at this stage is that of establishing a personal identity.

24. Developmental changes in the life span • Healthy adults, according to Erikson, can find satisfaction in relations with others. • The psychosocial issues in adulthood involve intimacy, which occurs with another person, and generativity, which concerns future generations.

25. Heritability • Heritability describes the extent to which variation among members of a group can be attributed to genes. Heritable individual differences in traits such as height or intelligence need not explain group differences. • Genes mostly explain why some are taller than others, but not why people today are taller than a century ago. • Developmental psychology is concerned with studying the shape of within-person change in central domains of functioning across the entire human life span. Of particular relevance is the identification of antecedent conditions, correlates, and consequences of those trajectories as well as their interrelations and modifiability

27. Evolutionary psychology • Evolutionary psychologists seek to understand how natural selection has shaped our traits and behavior tendencies. The principle of natural selection states that variations increasing the odds of reproducing and surviving are most likely to be passed on to future generations. • Some variations arise from mutations (random errors in gene replication), others from new gene combinations at conception. Charles Darwin, whose theory of evolution has for a long time been an organizing principle in biology, anticipated the contemporary application of evolutionary principles in psychology.

30. Evolutionary psychology basically attempts to explain human psychology in terms of adaptive evolutionary principles.