The nature/nurture debate in intelligenceIntroductionThis paper will examine the nature-nurture debate regarding the development of human intelligence. This topic has interested psychologists ever since the concept of intelligence was formalised and measurements of intelligence were devised. In this context, ‘nature’ refers to people’s innate, inherited or genetic potential, while ‘nurture’ refers to the influence of the social environment, education, culture and so on. The paper outlines the history of the field of intelligence testing and theory, and the contributions of individual psychologists are described and assessed. The current situation regarding the nature-nurture debate is mentioned, and an attempt will be made to show that both nature and nurture are important in the development of intelligence.
The interaction between nature and nurture is what counts, and it is impossible to prove that either one is more important than the other. Construct measurementIntelligence is a construct, and constructs are abstract ideas which are used to explain an observed phenomenon (Rosenthal & Rosnow, 1991). A child who scores well on both mathematics and English tests might be inferred to have a high intelligence, based on the available evidence.
However, intelligence, like any other construct, is not directly observable, as are physical qualities such as height, weight or hair colour. This means that whatever is being measured is not necessarily the construct in question (Rosenthal & Rosnow, 1991). It is possible that the test is assessing the child’s education rather than intelligence, or a combination of both. The history of the concept of intelligenceSir Francis Galton was the first scholar to suggest that intelligence is hereditary. His personal life probably shaped his viewpoint, since he was born into an affluent family and Charles Darwin was one of his cousins (Weiten, 1989; Bulmer, 2003).
Galton studied family trees and saw that eminence and success seemed to run across generations within the same families. In 1869 Galton published the theory that this success was due to genetic superiority. However, what he failed to acknowledge was that these families were usually the wealthiest ones, where individuals were very well-educated and enjoyed social influence (Weiten, 1989). Galton conducted twin studies, using both genetically similar (identical) twins and non-identical twins, to tease out the influence of nature versus nurture (Bulmer, 2003).
Galton became convinced that nature (genes) was the stronger of the two influences. He was so sure of his theory of genetic superiority that he went on to build the concept of eugenics, where he envisaged that only genetically ‘superior’ people should marry and breed, thus eventually improving the quality of the entire human race (Weiten, 1989). These days, eugenics are associated in many people’s minds with the Nazi atrocities of World War II, where Jews, disabled and intellectually handicapped people and other groups whom the Nazis deemed to be genetically inferior were ruthlessly exterminated on a mass basis. Galton also theorised that higher intelligence would be associated with superior sensory reaction times.
He carried out research to test this hypothesis, and found that it was not true. These experiments had an unexpected spin-off in that they led Galton to develop the idea of statistical correlation, and showed that measuring mental ability might be possible (Weiten, 1989). Galton was also a pioneer in studying normal distributions (Bulmer, 2003), in which most members of a population possess an average amount of a trait or ability, with few people possessing either above- or below-average amounts (Rosenthal & Rosnow, 1991).