Genes were described by Ken Richardson (1994) as segments of chromosomes, which located in the nucleus of a cell. Genes are chemical substances and composed of deoxyribonucleic acid (DNA). DNA produces specific enzymes that involved in chemical reactions, product of which is a part of a cell. Each body cell contains 23 pairs of chromosomes, However, sperm and ovary, which is are called games, contain only 23 individual chromosomes. When a sperm and an ovary formed a single cell, their chromosomes combined. The set of individual’s genes is called genotype. A variation in characteristic’s appearance is called phenotype.
Psychologists that supported the view of genetic determinism believed that a child inherited the majority of psychological characteristics from his parents and there is little to do to change them. Such view was demonstrated by Nativits, who believed in innate abilities of human beings. Noam Chomsky (1980) argued that development of physical and psychological characteristics corresponded with one another. That could have been shown on the example of brain development. With the development of the brain mental abilities increased. However, it suggested that after the brain of a child was developed, mental abilities stayed stable, which was not true. Mental abilities of a human being are changeable through life.
Piaget (1980) proposed that the development of some characteristics were not simply genetically determined but developed in the course of development. That was called developmental plasticity. Information acquired in the course of development was placed “above and over” (Richardson, 1994, p66) of that in the genes and was called epigenetic information. Psychological characteristics could have been developed in that manner. This process made human beings more adaptable to the rapidly changing industrial and technological world. Psychologists who supported that view were supporters of Constructivist’s position on child development.
Charles Darwin’s Evolutionary theory showed that in the world of biological species there was a process of selection of more advantageous characteristics in respond to changing environmental settings in order to reach adaptation. Many psychologists tried to explain the evolution of psychological and social characteristics in the same manner. Ken Richardson (1994) showed that a new born had a number of reflexes that were considered as evolutionary selected in order to survival. Rooting reflex appeared as head-turning and mouth opening behavior of an infant when his cheek is stroked. Predispositions of a child to social interactions could have been shown on examples of innate abilities of infants to smile and cry in a specific way. These abilities are also evolved in order to better survival.
Interaction between genes and environment is a complex process and thus, poorly described. There is a problem with an identification of such interactions. The majority of characteristics controlled by a number of genes or a single gene control several characteristics. There were little possibilities to investigate such interactions. In the experiment on animals, for example, genes could have been controlled b selecting breeding and the environment by keeping and animal in a certain condition. It is not possible, certainly, to imply such a control to a study with human participants because of the ethical implications. Natural settings pose a problem of controlling variables. It is complicated to identify the effect of a particular environment or particular gene because of the number of confounding variables, which accompany them. All these implications often led to a hypothetical description of such interactions.
There were methods, however, which were used to study gene-environment interactions. Family studies investigated and impact on child’s development of inherited genetic information and impact on child’s development of inherited genetic information and the rearing environment. Twin studies investigated extend of genetic and environmental influences on development. Adoption studies concerned with how psychological characteristics of adopted children correlated with biological and adoptive parents. Methods, usually used in such studies were observations and questionnaires.
Interaction of genes and environment could be noted if a single gene is absent or its functionality is altered. Phenylketonuria (PKU) is a condition where the production of en enzyme by a gene is absent. As a result the conversion of phenylalanine into tyrosine did not occur and that led to the disruption of development of mental abilities. Phenlalanine was not produced by and organism and entered it with the food. As a result, the treatment of such condition is not exclude phenylalanine from the diet. Child’s development then occurs to be normal. This example showed the importance of investigations of gene-environment interactions.
Studies of gene-environment interactions tend to uncover the reason of people’s individual differences. Development of intelligence and temperament were studied using methods, mentioned above. There were found significant correlations, which continued to make those methods useful.
The Texas adoption project (Horn, 1983) studied the extent to which hereditary factors played a role in development of intelligence. There were 300 families participating in that study. It was found that the IQ of adopted children correlated closer to their biological parents then to adoptive ones. However, child’s placement from less to more advantageous environment, which was usually considered to be a family environment, showed that child’s IQ level in such situations was raised. That demonstrated the importance of environment on child’s development as well as biological factors.
Although a child inherited some psychological characteristics from his parents, those characteristics tended to play a role of pre-dispositions. Further development was also dependent on the environment, where a child was placed.
Interaction between genes and environment was better described by Stevenson and Oates (1994) and Schaffer (1996pp. 79-90) on the example of interaction between ingerited temperamental characteristics and environment. The knowledge of such interactions supposed to predict the consequent developmental our comes and to make the necessary interventions on time. Temperament was defined as behavioral style. This term concerned with aspects of behavior, which appeared to be constant through life.
There was a debate amongst psychologists about the classification of temperamental characteristics. One of the classifications was proposed by Bates (1989). According to that classification behavioral style was characterized:
• Emotional responses, It included the quality and intensity of emotional reactions.
• Attentional orientation patterns, such as how quickly a child could have been comforted and the sensitivity to distractions when occupied by a task.
• Motor activity included the intensity and frequency of child’s activity.
There was also description of an easy and difficult temperament. Difficult temperament had such characteristics as irregularity, negative mood and low adaptability. Easy temperament was described as opposite to that of difficult. The methods, which were used to identify heritability of temperament, were observations and parental reports. It was likely to conclude that there was some evidence of heritability. However, the developmental outcomes depended also on the environment, which was encountered by a child in the course of development. Different temperamental characteristics were likely to provoke different parental responses to a child. In that was there was an interaction between a child’s genetic inheritance and the environment. This view of temperament supported Constructivist position.
Thomas and Chess (1977) noted the importance of a match between child’s temperament and parental treatment of a child. So, even if a child with initially easy temperament encountered non-suitable expectations and demands of his caretakers there could have been shown negative developmental outcomes. This concept was known as “goodness of fit”.
Understanding of gene-environment interaction is important for understanding child development. The immense importance of such understanding could be seen on the example of knowledge about the roots of philketonuria. Without it normal development of a child who has such a condition could not be possible. Understanding of developmental processes of temperament and intelligence and interaction of them with environment might predict developmental outcomes. Knowing that it could be possible to intervene on time and prevent negative developmental endpoint. Unfortunately, science has not yet developed methods by which it could be possible to accurately investigate gene-environment interactions and take into accounts all confounding variables. However the investigation of this matter can not be abandoned only because of not knowing enough at the present since the process of combination of parental genetic information makes a basis for emergence of a new life and different environmental settings give different impact on child development.