Feral children provide another opportunity to study the nature/nurture issue. Typically, the cases of feral children get much more attention than the normal, more scientific methods of researchers. Feral children are children who appear to grow up in the wild or to be brought up by animals. These children seem to have had very little, or no, human contact while they were growing up. Feral children would seem to support the conclusion that experiences (i.e., nurture) are important to the normal development of the human brain. If these children experienced deprived environments in their youth, then these deficient environments led to them developing very poorly and with many cognitive deficits compared to normal human children. As promising for studying the nature/nurture issue as these cases might seem to be, they are few and far between, so they amount to nothing more than case studies that capture a lot of attention. Candland (1993) discusses the stories of many feral children such as Peter, Victor (the Wild Boy of Aveyron), and the wolf-girls of India. In the end, however, real-life examples of feral children have too many unanswered questions to provide accurate information concerning the nature/nurture debate. For instance, exactly where and when were these children abandoned, and exactly why were these children abandoned? It may be that these children were severely disabled to begin with and this may be the very reason that they were abandoned in the first place. If this is so, then these children really do not provide unique information about the nature/nurture issue. As is usually the case with real-world examples, the number of uncontrolled factors is so numerous that no conclusive data can be obtained from the reported cases of feral children. Nonetheless, these cases will continue to garner a large amount of attention, and they provide a more human face and emotional connection to the nature/ nurture debate.
In psychology today, researchers have a number of methods that help them to identify the extent to which nature and nurture influence psychological traits. First, twin studies involve the comparison of identical and fraternal twins. Identical twins develop from the same fertilized egg, so they are called monozygotic (MZ) twins. Identical twins have the same genetic makeup, so their genetic relatedness is 100 percent. Thus, any differences found between identical twins can be attributed to the environment (i.e., nurture). Fraternal twins, on the other hand, develop from two separate fertilized eggs, so they are referred to as dizygotic (DZ) twins. Fraternal twins are like any two siblings with a genetic relatedness of 50 percent. This difference between identical and fraternal twins in genetic relatedness is key to drawing conclusions about nature and nurture from twin studies. With this basic knowledge of genetic relatedness of twins one can make conclusions based on correlations between twins on a particular psychological trait. If a trait is influenced by nature (heredity), then researchers should find that fraternal twins are more variable (or different) on that trait as compared to identical twins. Because identical twins have the exact same genetic input, researchers should not observe any differences between them on a trait that is hereditary in nature. However, if a particular trait is not influenced by nature, then researchers should find that identical twins are not any more similar to each other on that trait than fraternal twins are to each other (Dunn & Plomin, 1990; Plomin, 1990). Another method that researchers use to study the influence of nature and nurture on psychological traits is adoption studies. Some adoption studies examine individuals who are not genetically related to one another, however they all live in the same environment (i.e., family). Other adoption studies examine individuals who are genetically related to one another, but they are raised in different environments. If nature is a key component for a trait, then individuals who are genetically related to one another (irrespective of their environments) should be similar on that trait. However, if nurture is a key component of a trait, then individuals who share a particular environment should be similar on that trait (irrespective of their genetic relatedness; Dunn & Plomin, 1990).
Although psychology in the 21st century is a scientific field that has developed many methods to investigate psychological phenomena, and our understanding of development has become more sophisticated, the nature versus nurture debate remains very active. An example of part of this continuing debate that will exist for the foreseeable future is the heritability of intelligence. Since Galton and Goddard argued that intelligence is essentially inherited, there have been researchers who have supported this conclusion. Over the years aspects of this debate have become part of the more unseemly beliefs of racism. Not that those who conclude that intelligence is inherited are racist, but that conclusion has in the past been partly motivated by racist beliefs against immigrants. This should demonstrate how volatile the nature versus nurture debate can be and how potentially important and influential research findings in this area are. In 1994 Herrnstein and Murray argued that intelligence was indeed a general cognitive ability on which humans differ, that IQ scores do not fluctuate much over the life span, and most importantly, that intelligence is largely heritable. Although behavioral genetic research tends to support the conclusion that intelligence is indeed substantially influenced by nature, most researchers today emphasize an interactionist perspective that recognizes the importance of both nature and nurture even when perhaps a majority of a trait, like intelligence, might be attributable to nature.
The debate concerning the heritability of intelligence is one example of a continuing issue, and a vigorous one at that, in the nature versus nurture debate. Providing viewpoints from both sides of the debate demonstrates some of the complexities that will continue to keep this debate an important part of psychology over the next century. Although some still argue that either nature or nurture is the most important influence on human beings and their psychological traits, the future seems to be focused on interactionist approaches that will attempt to better explain how nature and nurture interact to make us who we are psychologically.
Even though the focus of most psychologists today is on the interaction of nature and nurture, there are still some theoretical approaches that emphasize the importance of nurture. Ericsson, Nandagopal, and Roring (2005) argue for the nurture side of the debate. They argue that expert performance does not rely on an inherited talent or giftedness; rather, expert performance is the result of acquired abilities that have been developed through extended deliberate practice. Ericsson et al. (2005) argue that evidence supports the conclusion that, contrary to experts in a given domain being born, before one can perform expertly in a given domain he or she must have prolonged experience in that field. Furthermore, they point out that a person’s performance in a specific area improves gradually over time and with experience; even the performance of so-called child prodigies follows this pattern. Ericsson et al. also argue that the historical improvements in performance over the last 100 years support the conclusion that expert performance is not due to innate talent. They point out that if talent were genetic, then improvements in talent over the last 100 years would not be possible because genes would fix an upper limit on talent that could not change dramatically in so short a time period. So according to Ericsson et al., their expert-performance framework attributes differences in expert performance (even among so-called prodigies) to acquired cognitive and physiological changes that are the result of extended deliberate practice.
Research investigating the nature and nurture issue in a variety of areas (e.g., intelligence, personality, mental illness, etc.) has potential applications. Knowledge about the causes for mental illnesses, for instance, directly affects the treatment that professionals will use for people suffering from those illnesses. For example, the discovery of substantial heritability rates for some mental illnesses, such as bipolar disorder, supports the continuing medical search for biological treatments, such as drugs. Furthermore, knowledge concerning exactly what parts of the environment influence mental illness can help psychologists to develop more targeted psychological treatments. In addition, the extent to which researchers believe that intelligence and personality are influenced by the environment can help to determine educational approaches from preschool through college.
In the early 20th century a new school of thought in psychology began to dominate the discipline, and this approach swung the pendulum all the way to the opposite end of the debate. Behaviorism emphasized the role of nurture and the environment in influencing individuals and their behavior. John Watson, the founder of behaviorism in America, denied that there were any inherited influences on human behavior. Instead, Watson made the bold claim that if he were given infants, then he could make one a doctor, another a thief, another a painter, and so on. He would merely need to control and manipulate the environment in which an individual developed. Any hereditary factors were unimportant and irrelevant to the development of the individual. So psychology passed into a period when there was a strong bias toward the nurture side of the debate (Hergenhahn, 2005). This emphasis on the environment was so strong that many psychologists believed that a phenomenon like the infant-mother bond was not in any way related to nature. Instead, it was argued that the infant-mother bond developed as a result of the mother (a neutral stimulus) being paired with primary reinforcers (e.g., food, milk, etc.).
The nature versus nurture debate stretches all the way back to the earliest days of Western philosophy, when Plato essentially believed that knowledge was inborn in humans and we merely needed to recollect this knowledge (although Plato did not believe that this was necessarily an easy process). We can firmly place Plato’s position on the nature side of the debate. On the other hand, we can firmly place another major figure in Western philosophy, Aristotle, on the nurture side of the debate. According to Aristotle, true knowledge was not inborn but came from one’s experiences with and observations of the physical world. This debate has been reincarnated repeatedly throughout the history of Western civilization. For instance, many centuries after Plato and Aristotle, the German rationalist Emanuel Kant and the British empiricist John Locke were laying out positions on opposite sides of this same debate. Of course, it was Locke who popularized the notion of the human mind as a tabula rasa (blank slate) at birth, meaning that individuals are not born with innate knowledge; rather, any knowledge or ability that a person eventually attains will have come about through that individual’s experiences. This places Locke firmly on the nurture side of the debate. On the nature side of the debate was Kant. Kant believed that before the mind could make any sense of its experiences there had to be an innate structure to the mind that enabled it to perceive the world and give meaning to one’s experiences. It was this innate ability of the mind that was most important to the attainment of knowledge. Whereas Plato, Aristotle, Locke, and Kant were primarily concerned with how humans can gain knowledge, modern psychologists are more interested in factors such as intelligence, personality, and mental illness. Thus, the nature versus nurture debate has a long history in Western culture (Hergenhahn, 2005). This research paper, however, will focus on the nature versus nurture question in psychology.
The nature versus nurture debate has a long history in Western philosophy and modern psychology. The debate is relevant to many different areas of study in psychology, including intelligence, giftedness, sexual orientation, personality, and mental illness. Today, most psychologists take an interactionist approach that views both nature and nurture as being important in development. However, some researchers still emphasize either nature or nurture as being the key component that determines a psychological trait. Many psychological researchers will continue to use tried-and-true research methods such as twin and adoption studies to examine the nature/nurture issue; however, future genetic research will identify more genes that influence behavioral and psychological phenomena. Future research on environmental factors will focus on the importance of nonshared environments and how different children in the same family might experience the same environmental stimulus in different ways, thus having a very different influence on their development. Research findings regarding nature and nurture will continue to be among the most applicable aspects of psychological studies, but they will likely also remain among the most politically volatile issues in the field.
One of the most persistent issues in the field of psychology is the nature versus nurture debate. This debate concerns how much of an individual, and who s/he is, can be attributed either to nature (i.e., inborn tendencies or genetic factors) or to nurture (i.e., learning or environmental factors). This debate can be one of the most contentious issues in psychology because of the potential serious political ramifications of nature/nurture findings (de Waal, 1999). Although the science of psychology has entered the 21st century, it seems that the nature versus nurture debate will continue to be an active part of psychological research for many areas, including research on intelligence, personality, and mental illness. This research paper will begin with a general overview of the history of the nature/nurture question, focusing on the history of psychology and how psychologists have emphasized the different sides of this debate over time. Next, we discuss current approaches in psychology relevant to the nature/nurture debate and possibly the most controversial aspect of this debate today (i.e., the heritability of intelligence). In addition, the research methods that psychologists have at their disposal to help them determine whether a trait has genetic or environmental influences will be described. Lastly, we discuss the complexities of trying to apply research from the nature versus nurture debate.