Role of Heredity and Environment in Individual Differences

No man is created equal. He differs from one to another is various aspects

Heredity and Environment—

Some events in life, such as achieving sexual maturity, are mostly governed by heredity. Others, such as learning to swim or use a computer, are primarily a matter of environment. But which is more important, heredity or environment? Let’s consider some evidence on both sides of the nature-nurture debate.

 

Heredity

Heredity (“nature”) refers to genetically passing characteristics from parents to children. An incredible number of personal features are set at conception, when a sperm and an ovum (egg) unite.

Genes are small areas of DNA that affect a particular process or personal characteristic. Sometimes, a single gene is responsible for an inherited feature, such as eye color. Most characteristics, however, are polygenic (pol-ih-JEN-ik), or controlled by many genes working in combination. Genes may be dominant or recessive. When a gene is dominant, the feature it controls will appear every time the gene is present. When a gene is recessive, it must be paired with a second recessive gene before its effect will be expressed.

Various areas where heredity has an influences in creating individual differences are-

1.   Human growth sequence- 

 

Its the  overall pattern of physical development. To a degree, genetic instructions affect body size and shape, height, intelligence, athletic potential, personality traits, sexual orientation, and a host of other details.  Heredity determines eye color, skin color, and susceptibility to some diseases.

2.   Temperament-     

Difference in temperament is evident even in newborns. This is the physical core of personality. It includes sensitivity, irritability, distractibility, and typical mood. About 40 percent of all newborns are easy children, who are relaxed and agreeable. Ten percent are difficult children, who are moody, intense, and easily angered. Slow-to warm-up children (about 15 percent) are restrained, unexpressive, or shy. The remaining children do not fit neatly into a single category

3.   Intelligence-

The closer two people are on a family tree, the more alike their IQs are likely to be.

4.   Personality-

  

 Twins and Traits indicate that personality is hugely influenced by heridity. For two decades, psychologists at the University of Minnesota have been studying identical twins who grew up in different homes. Medical and psychological tests reveal that reunited twins are very much alike, even when they are reared apart. Typically, they are astonishingly similar in appearance, voice quality, facial gestures, hand movements, and nervous tics, such as nail biting. Separated twins also tend to have similar talents. If one twin excels at art, music, dance, drama, or athletics, the other is likely to as well— despite wide differences in childhood environment.

Environment

Environment (“nurture”) refers to the sum of all external conditions that affect a person. The environments in which a child grows up can have a powerful impact on development. Humans today are genetically very similar to cave dwellers who lived 30,000 years ago. Nevertheless, a bright baby born today could learn to become almost anything—a ballet dancer, an engineer, a gangsta rapper, or a biochemist. But a baby born 30,000 years ago could have only become a hunter or food gatherer. In short, environmental forces guide human development, for better or worse, throughout life.

1.   Sensitive Periods

These are times when children are more susceptible to particular types of environmental influences. Events that occur during a sensitive period can permanently alter the course of development. Certain events must occur during a sensitive period for a person to develop normally. For example, forming a loving bond with a caregiver early in life seems to be crucial for optimal development. Likewise, babies who don’t hear normal speech during their first year may have impaired language abilities 

2.   Prenatal Influences

 

The impact of nurture actually starts before birth. Although the intrauterine environment (interior of the womb) is highly protected, environmental conditions can affect the developing child. For example Teratogens- Anything capable of causing birth defects is called a teratogen. Sometimes women are exposed to powerful teratogens, such as radiation, lead, pesticides etc can cause mental retardation in children.

3.   Intelligence-

 

a.    Strong evidence for an environmental view of intelligence comes from families having one adopted child and one biological child. Such children have shown strikingly similar IQ levels.

b.    Children adopted by parents of high or low socio-economic status- As you might predict, children who grow up in high-status homes develop higher IQs than those reared by lower-status parents. In one study, striking increases in IQ occurred in 25 children who were moved from an orphanage and were eventually adopted by parents who gave them love, a family, and a stimulating home environment. Once considered mentally retarded and unadoptable, the children gained an average of 29 IQ points. A second group of initially less “retarded” children, who stayed in the orphanage, lost an average of 26 IQ

c.    A particularly dramatic environmental effect is the Flynn effect, the fact that 14 nations have shown average IQ gains of from 5 to 25 points during the last 30 years (Dickens & Flynn, 2001; Flynn, 1990). These IQ boosts, averaging 15 points, occurred in far too short a time for genetics to explain them. It is more likely that the gains reflect environmental forces, such as improved education, nutrition, and living in a technologically complex society

Nature-Nurture Interactions

The outcome of the nature-nurture debate is clear: Heredity and environment are both important. Heredity gives us a variety of potentials and limitations. These, in turn, are affected by environmental influences, such as learning, nutrition, disease, and culture. Thus, the person you are today reflects a constant interaction, between the forces of nature and nurture.

 

1.   Reciprocal Influences

Because of differences in temperament, some babies are more likely than others to smile, cry, vocalize, reach out, or pay attention. As a result, babies rapidly become active participants in their own development. Growing infants alter their parents’ behavior at the same time they are changed by it. The reverse also occurs: Difficult children make parents unhappy and elicit more negative parenting (Parke, 2004).

Twin Studies indicate that the IQ scores of fraternal twins are more alike than those of ordinary brothers and sisters. identical twins, who develop from a single egg and have identical genes and grow up in the same family have highly correlated IQs. This is what we would expect with identical heredity and very similar environments.