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.
