Introduction
The problem of nature versus nurture reaches deep into the history of the European thought. One of the first debates on this topic may be found in works by such an Ancient Greek philosopher as Plato; however, the thinker discusses the origins of a broad category of characteristics, which he names virtues (Aldrich, 2014). The issue was widely discussed in the subsequent literature; however, the studies of the 20th and especially of the 21st century gathered some evidence which might finally shed light on this issue.
This paper is aimed at elaborating and investigating the approaches of “nature” and “nurture” with respect to the problem of development of an individual’s intelligence, that is, their ability to reason, learn and utilise knowledge and skills, solve various types of problems, and so on. More specifically, the approaches are defined, the models of development of intelligence according to the models are provided, and the two approaches are compared. After that, the question about the correctness of the models is answered; evidence from recent peer-reviewed journal articles is used in order to demonstrate that the strict classical dichotomy is, apparently, incorrect, and that some combination of the two types of factors (hereditary and environmental) may have an impact on the development of intelligence in persons.
Nature and Nurture Approaches: Definitions
The problem of origins of intelligence and its development in a person is one of the important problems which have been considered from the “nature vs. nurture” point of view. The position of the proponents of the “natural” origins of intelligence is that intelligence is an essential characteristic or quality of an individual (Aldrich, 2014). In the 20-21st century, the origins of this characteristic have usually been attributed to inheritable, genetic factors (Goldhaber, 2012). On the other hand, those who favour the position of “nurture” state that intelligence has its roots in the process of bringing up, learning, etc. (Aldrich, 2014); in other words, they believe that it is acquired from the external environment and from the experiences that an individual attains (Holtz, 2011). Of course, nowadays it is clear that an individual cannot obtain knowledge without being taught, so the proponents of “nature” state that biological factors define the ability of an individual to learn, utilise knowledge, engage in reasoning, and so on (Aldrich, 2014). On the other hand, the advocates of the “nurture” approach claim that intelligence is defined by one’s environment and conditions (Goldhaber, 2012). It is worth considering the ways in which, according to these two theories, intelligence develops.
Development of Intelligence According to the Two Approaches, and Changeability of Intelligence Through the Course of One’s Life
It is clear that the proponents of these two approaches have different views on the ways in which intelligence develops in an individual. Those who hold the belief that intelligence originates in “nature” are convinced that it is determined by biological (mainly genetic) factors at birth (or even earlier), and that intelligence does not change considerably over the course of one’s life (or, perhaps, even does not change at all, apart from the alterations resulting from maturation, and from the degradation caused by the process of ageing), similarly to the colour of one’s eyes or the shape of their hair (curly or straight); the processes of learning and teaching are considered to utilise intelligence, but not to change it in any way (Aldrich, 2014). Therefore, intelligence, according to the strict supporters of this model, is defined prior to the birth, and remains stable over the course of one’s life (Goldhaber, 2012).
On the other hand, the advocates of the theory of “nurture” allege that the behaviours and the intelligence of the human are learned in the course of one’s life from their environment (Holtz, 2011). In this case, the intelligence and the skills of an individual are completely dependent on their experience, and, therefore, can change throughout the course of one’s life (Goldhaber, 2012).
Thus, the strict proponents of the two theories have the opposite opinions regarding the origins and the formation of the intelligence.
Comparing the Two Approaches
The two models of intelligence have a number of implications which can be labelled as advantages or disadvantages. For instance, because, according to the “nature” point of view, an individual has a constant level of intelligence determined by their heritage, and this level cannot be altered, the phenomena aimed at cultivating people with higher intelligence, such as racism or eugenics, might arise (Aldrich, 2014); these phenomena are clearly destructive, as shown by history, and this is a serious disadvantage of this approach. Also, this model practically leaves no hope to those born in poverty, etc., for these people might automatically be branded an having low intelligence (Levitt, 2013). On the other hand, it is also pointed out that a theory according to which an individual’s ability to reason was restricted due to biological (e.g., “nature”) causes (minor age) was successfully used to prevent the imposition of guilt on adolescents, and saved the defendants from the capital punishment in a court case (DeLisi, Wright, Vaughn, & Beaver, 2010); therefore, this theory can also be used for beneficent purposes, which is clearly an advantage.
On the other hand, the theory of “nurture” emphasises the importance of one’s environment, which leads to the logical conclusion that for fuller development, one needs to be supplied with conditions that are appropriate for this (Goldhaber, 2012). The resulting need to provide children with good education and to raise them in appropriate conditions is clearly an advantage of the “nurture” point of view, which the other theory lacks. A possible disadvantage is that according to this position, people constantly living in adverse situations, such as impoverished persons, are also, ironically enough, almost deprived of the hope to “get better” unless the situation changes. Even though it is apparent that this is the general trend, the “nurture” theory does not explain exceptions from this rule.
Evaluating the Evidence
After discussing the two approaches in detail, it is crucial to consider the evidence supporting these theories in order to be able to decide which one is true (or “truer”). And, in fact, it should be stressed that most scholars agree that neither of the “pure” positions is true; instead, they both reflect the truth to a certain extent. Researchers sharply criticise the proponents of the “pure” approaches, stating that, e.g., psychiatry recognised the common influence of both nature and nurture, but “other fields in the social sciences continue to be hampered by the idea that social and biological variables compete for explanatory relevance” (DeLisi et al., 2010, p. 24); or that recent studies showing the impact of genetic factors on intelligence not only in childhood, but also in the old age, might “signal the end of the nature-nurture controversy” (Plomin, 2012, p. 165).
There is an abundance of evidence that both hereditary and environmental factors affect one’s intelligence. For instance, a study of twins by Brant et al. (2013) demonstrates that children who have higher IQ also tend to have a “sensitive period in IQ development” that lasts longer than that of kids with lower IQ, and that individuals experience “a shift away from environmental and toward genetic influences” at a certain point (p. 1492), thus being affected by different factors differently during various periods of their life. Another study of twins by Daw, Guo, and Harris (2015) discovered that, while the twins have common features attributed to genetic factors, some features of the environments that they share statistically significantly moderate (change the strength and/or direction of relationship) the impact of their non-shared environments on their intelligence and academic achievements; thus, both types of factors contribute to their development.
A surprising finding of 23 combined studies of twins (total N=7852) is that abilities which were most heritable among subjects were also the most culture-dependent ones (Kan, Wicherts, Dolan, & van der Maas, 2013). In addition, Plomin (2012) states that a large-scale analysis of numerous genomes from a large sample of non-related individuals revealed that there might be a connection between intelligence in childhood and old age, and that certain genetic factors might explain nearly 25% of variance of changes in intelligence estimates of a person during their life. Finally, Plomin, Shakeshaft, McMillan, and Trzaskowski (2014) in their study of a great number of twins aged 12 found out that more than 50% of the variance between proficient and normal readers was explained by genetic aspects; environmental factors also contributed to the children’s development, but in particular, such aspects as being raised in the same family and studying at the same school could only explain less than 20% of the difference between proficient and normal readers.
It is easy to see that these studies, a certain amount of variance is attributed to genetic and hereditary factors, whereas the rest of the variance is explained by the environmental conditions. In addition, more difficult forms of interplay (such as moderation) have been discovered between certain environmental and hereditary factors affecting a person’s intelligence. Therefore, the conclusion seems clear: strictly differentiating between the “nature” and “nurture” approaches, considering them mutually exclusive, and adhering to only one of these models contradicts the evidence gained in studies and might be considered obsolete; it is not surprising, therefore, that this strict differentiation has been called outdated, naive, or a false dichotomy (Levitt, 2013). Instead of this, it is recommended to carry out further studies aimed at uncovering which aspects of one’s intelligence are dependent upon which elements of their environment and on what genetic factors, as well as at unveiling the possible interactions between different factors affecting one’s development (Levitt, 2013).
Conclusion
Thus, according to the proponents of the “nature” approach, a person’s intelligence is defined by such hereditary factors as genes, whereas in accordance with the advocates of the “nurture” approach, environmental factors such as upbringing and education influence the formation of intelligence. However, the recent research shows that both hereditary (genetic) and environmental aspects have an impact on a person’s intelligence; both types of factors can explain considerable and statistically significant amount of variance in intelligence. Thus, it might be recommended not to adhere to any of the two named approaches, but to attempt to find out the exact mechanism of influence of factors of both types on the intellectual capabilities of an individual (Levitt, 2013).
References
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