Nature vs. Nurture

The dubious history of the heredity environment controversy can be
easily traced as far back as the start of the present century with at least some
historical evidence placing the roots of this dispute in the time of John Locke.
This controversy has continued despite continual reiteration that the critical
question is not how much of a trait is due to heredity and how much is due to
environment, but rather how environment transact to influence development.” (
Wachs , 1983, p. 386).
This paper will focus on the nature/nurture controversy and the extent
to which an individuals intellectual level is determined either by inborn
intelligence or by environmental factors.
The relative powers of nature and nurture have been actively pursed by
psychologists and biologists striving to determine how heredity and environment
influence the development of intelligence.
Before we can go on to discuss the relationships between intelligence
and the controversy that exists between the different schools of thought
regarding inherited or environmental issues we must have an understanding of
what intelligence really is.
Of all the words used in pressed day psychology, intelligence is one of
the most difficult to define and is also one of the most controversial. There
is however, a general agreement that intelligence refers to the overall
faculties of the mind which concern themselves with the sorting of information
in the brain after it has been received by the senses, the perceiving of
relationships between this new data and information which is already in memory,
and the capacity to make rapid and appropriate decisions as a result of the
previous processes.
The intellectual faculties of the brain are dynamic and interactive and
relate to the capacity of the central nervous system to respond speedily and
appropriately in a rapidly changing and potentially threatening environment.
Raymond J. Corsini provides us with a somewhat more simplistic
definition of the term intelligence. According to Corsini (1984) the term
intelligence can be employed to indicate the amount of knowledge available and
the rapidity with which new knowledge is acquired; the ability to adapt to new
situations and to handle concepts, relationships, and abstract symbols.
While the heredity/environment topic continues to be a controversial
issue, a great deal of evidence has been gathered to support both arguments.
In order to investigate the topic of nature/nurture it is important to
consider a variety of research elements. Among these elements are some of the
most relevant issues pertaining to this subject including: twin, adoption,
family, orphanage life, IQ, and race studies. It is to these studies we will
now turn our attention.


The importance of twin studies is evident if we look at the studies
objectively, if intelligence is basically hereditary, identical twins who have
the same genetic legacy, should be concordant for that trait than are fraternal
twins, which are no more alike genetically than other siblings.
Burt\'s (1958) famous study show that the intelligence test scores of
identical twins, whether reared together or apart , display considerably higher
correlation than the scores of fraternal twins.
Burt\'s work is currently viewed with caution due to the manner in which
he gathered and interpreted his data (Vernon, 1979). However, Burt\'s research
provides an important foundation for this research.
Jone\'s study (1946) shows that there is a modest difference in the
intelligence test scores of twins reared apart, and the more divergent the
environments, the greater the difference.

“While environmental factors are important in raising or lowering a
child\'s level of intellectual performance, these studies demonstrate that they
only do so within limits set by heredity.” (Mussen, Conger, and Kagon, 1963

The Louisville Twin Study (Wilson, 1983) showed that environmental
considerations such as characteristics of home and the interaction of the mother
with the infant, have a prominent effect upon the infant\'s mental development.

Vermon (1979) concludes that we may attribute 60 percent of the
determination of IQ status to heredity, 30 percent to environment and 10 percent
tot he combined effects of the two.
David Layzer\'s (1976) study indicates that the more relevant a given
task is to an individuals specific environmental challenges, the more important
are the efface of this interaction. A child grown up in circumstances that
provide motivation, reward and opportunity for the acquisition of verbal skills
will achieve a higher level of verbal proficiency than his twin reared in an
environment hostile to this id of development.
According to Layer if two egg twins are reared together we cannot assume
the environmental factors are the same for both. If one twin has a greater
verbal aptitude he will devote more time