Heredity and the environment in Psychology

Differential Psychology uses the knowledge provided by genetics when it addresses the attempt to explain individual differences at the level of ultimate or distal causes. Numerous studies carried out during the last decades have focused on this issue and whose Future discoveries are increasingly promising due to methodological and technical advances in genetic matter. There is a differentiation between the two lines of research that are most relevant: Quantitative Genetics, It encompasses the studies that are responsible for elucidating the weight of genetics and the environment in the different characteristics in which humans show differences. This study is approached from a quantitative point of view and it includes the studies of families, twins, adoptions and mixed models. Study of the effects of genes and chromosomes where molecular techniques are used to obtain the observation of the composition of the hereditary material. These observations allow us to contrast properties that classical or Mendelian genetics could only infer. Here the interest shifts from "how much" to "how" genes act to produce individual differences.

Index

1. Quantitative strategies aimed at elucidating the weight of heredity and the environment
2. Population Genetics
3. Quantitative Genetics
4. The Genetics of Behavior
5. Theoretical proposals about the classification of the environment

Behavioral Genetics has facilitated the analysis of the relative weight of Heredity and the environment in the explanation of different human behaviors. However, such a discipline does not provide information on the ultimate causes of individual behaviors, nor on the causes underlying the differences between human groups in the aspects studied, nor does it have the appropriate methods to get them. The results of the Genetics of Behavior are limited to informing about the proportion in which the variability presented by a group of individuals, with respect to a studied characteristic, it can be attributed to genetic or environmental factors, using a methodology statistics. In order to place ourselves theoretically and methodologically in the right place, the differences and similarities between objectives and scope of study of: Population Genetics, Quantitative Genetics and Behavioral Genetics.

The first studies linking the phenotypic traits or manifest and genetic had the claim to determine for each trait the existence of a gene. His research is aimed at elucidating the rules and the effects that monogenetic inheritance has on a population of individuals. Study the effect of particular genes on specific aspects. Talking about Population, refers to any group of individuals that have the probability of crossing each other. Studies of differences between races have been a traditional prototype of differential psychology.

The differences that humans shown in the color of the skin, it is due to adaptation to the environment through numerous generations. In the case of hot countries, darker skin protects from solar radiation and prevents diseases such as cancer of skin, favoring the reproduction of individuals with darker and thicker skin and hair, to protect themselves from Sun. In colder areas, white skin is more adaptive as it allows greater absorption of Vitamin D through the few available sun rays. An exception would be the Eskimos since they are assured of the contribution of vitamin D by consuming fish intensively.

Its objective is to determine the weight of inheritance and not just the gene. The quantification of genetic factors and environmental, is carried out through different designs (of families, twins, or adoptions) and a methodology statistic that allows estimating its degree of heritability and environmentality in a population, for a variable determined. Heritability always refers to a population that lives within a range of precise means, as specified by Beckwinth and Alper in 1998. 3)

It was born as a branch of Psychology, closely linked to the study of individual differences and reached its own entity in the sixties. Its objective is one of the interests of Differential Psychology, the investigation of the influence hereditary in psychological or behavioral aspects, and in return also the influence environmental. Given that most human behaviors and that are the object of interest psychological are influenced for more than one gene, the Genetics of Behavior welcomes a quantitative study to study the influence of inheritance, being more relevant and useful in the psychological study of individual differences than the Genetics of Populations. In the eighties, the contributions within this field of study began to achieve the recognition they deserved, positioning themselves as a point of reference in the overcoming of the confrontation existing until then between the supporters of inheritance (Eysenck, Jensen or Plomin) and those of the environment (Kamin, Lewontin or Gould). The studies carried out on the Genetics of Behavior have evolved since its birth as a scientific discipline. Three changes stand out that shed more light on the relative contribution of genetics and environment to human psychological variability:

• The passage of monogenetic models (typical of population genetics) to the polygenetic (studied under the quantitative perspective. Already at the beginning of the s. XX Pearson (Galton's disciple) noted the improbability that most phenotypic characteristics were linked to a single gene.
• The passage of a conception of heredity under which a direct relationship between genes and behavior is interpreted, towards an indirect consideration of these relationships. Currently, it is assumed that the relationship between genes and behavior is modulated by a series of physiological factors. Genes do not fix behavior. They only act by encoding an amino acid, which will form part of a protein and this one of a tissue in a physiological process or function.
• The abandonment of additive models, whose objective was to find out the proportion of variance due to genetic and environmental factors, in favor of interactive models. The Genetics of behavior, proposes a linear model in which it is possible to distinguish 5 components that form the phenotypic variance of a trait in a population:

1. Genotypic variance, referred to the proportion of variability with respect to a characteristic that presents a population explained by genetic factors.
2. Environmental variance, proportion of the variability of a characteristic observed in a population that is explained by environmental factors. A distinction is made between: common environmental variance or shared by the different members of a family (variance between families). specific variance o Intra-family variance is attributable to the particular experiences of each of the family members. Inside of the shared family atmosphere there are variables such as socioeconomic status, type of home and its location (rural or urban), cultural level of parents and people around them, general upbringing guidelines, etc. Regarding the specific environment, which is not shared by the members of a family: group of friends, attendance at different schools, differential treatment received based on sex or birth order.
3. The covariation between genes and environmentIt refers to the differential exposure of different genotypes to various environmental influences. They can be of three types: Passive. The parents themselves transmit the genotype and the favorable environment for the development of a trait. Reactive. When it is the expression of the genotype that generates a favorable reaction in the environment to the development of said trait. Active. When it is the subject himself who actively seeks an appropriate environment for the development of his genotypic characteristics. The relationship that exists between genes and the environment is related to the role played by people in the construction of their personal environments, avoiding being mere passive victims of their environment.
4. The interaction between genes and environment. When the combined effects of genetics and environment increase vulnerability beyond a certain threshold, the disorder manifests itself.
5. Variance error, accounts for the proportion of variability that we cannot clearly attribute to genetic or environmental factors.

Within the scope of Behavioral Genetics, the distinction made regarding the environment, between the effect of common variance and the effect of the specific variance, does not adequately solve the operationalization environmental.

Plomin, DeFries and McClearn (1980) distinguished between active, passive and reactive correlations, served as a starting point for Scarr (1996) to elaborate a individuality theory in which the notion of "construction of a niche" stands out. Scarr argues in his theory that as individuals mature, they seek, construct, and create environments that correspond to their inherited personal characteristics, in which to develop their personality, interests and their capabilities.

Studies carried out on adolescents' perceptions of their family environment demonstrate a genetic influence on the way these adolescents evaluate their parents. The works of Ceci stand out, an author who suggests a modelBioecological of intelligence that emphasizes the role of different cognitive potentials. From her work it is clear that cognitive abilities are closely related to the years of schooling of the subjects.

This article is merely informative, in Psychology-Online we do not have the power to make a diagnosis or recommend a treatment. We invite you to go to a psychologist to treat your particular case.

If you want to read more articles similar to Heredity and the environment in Psychology, we recommend that you enter our category of Personality and Differential Psychology.