Differential Psychology: history, objectives and methods

Differential psychology, which analyzes variations in behavior of people, has evolved a lot since Galton founded his Anthropometric Laboratory, a milestone in the study of individual differences. At present this branch of psychology focuses its efforts on determining the relative influences of heredity and environment on behavior.

In this article we will briefly explain the historical development of differential psychology, describe the objectives and methods of this discipline, and clarify how it differs from personality psychology, a very close discipline in some ways.

• Related article: "Differences between personality, temperament and character"

History of differential psychology

In the mid-nineteenth century the monk Gregor Mendel carried out the first genetic studies of which there is evidence. Using peas, Mendel determined the laws of inheritance, made advances for the future concept of "Gene" and coined the terms "dominant" and "recessive" in relation to the heritability of traits biological.

A few decades later Francis Galton, relative of Charles Darwin, became a pioneer of differential and personality psychology by developing the psychometry. The student and protégé of Francis Galton, the mathematician Karl Pearson, made fundamental contributions to the field of statistics and questioned Mendelian laws.

The rise of behaviorism weakened the influence of differential psychology, which resurfaced in the 1960s and 1970s with the publication of Behavioral geneticsby John Fuller and Bob Thompson. These authors introduced discoveries of genetics into differential psychology that explained phenomena such as mutations and polygenic transmission.

Despite advances in differential psychology and behavioral genetics, it remains Difficult to separate hereditary from environmental influences when studying behavior and mind human.

• Related article: "History of Psychology: main authors and theories"

Objectives of this discipline

The main objective of differential psychology is quantitatively investigate the differences in behavior between individuals. Theorists and researchers in this discipline seek to determine the variables that cause behavioral differences and that influence their manifestation.

Differential psychology focuses on three types of variations: interindividuals (differences between a person and the rest), intergroup, which take into account variables such as biological sex or level of socioeconomic, and intraindividuals, which compare the behavior of the same person over time or in different contexts.

Despite the fact that differential psychology is frequently confused with that of personality, the branch in question investigates very varied topics: intelligence, self-concept, motivation, health, values, interests... However, it is true that the contributions of differential psychology to personality and intelligence.

Since its inception, the psychology of individual differences has been applied in educational and professional settings, although its usefulness depends on the phenomena that are investigated. It is also important to mention the usual relationship of differential psychology with eugenics, which aims to "improve" the genetics of populations.

• You may be interested: "Eysenck's Personality Theory: The PEN Model"

Research Methods

Differential psychology uses mainly statistical methods; thus, we work with large samples of subjects and data is analyzed from a multivariate approach. In this way, elements of experimental control are introduced that allow establishing relationships between variables. The use of observational and experimental methods is also common.

There are three types of research designs characteristic of differential psychology: those that analyze similarities between family members, animal designs, and those studying individuals raised in environments specials. Of this last type of design we can highlight the studies with adopted children, as well as the famous case of the wild child of Aveyron.

Between family investigations studies with monozygotic twins stand out, since they are identical at the genetic level and therefore their differences depend on the environment. However, and despite the obvious advantages of this type of design, it is difficult to distinguish the relative influences of the specific and shared environment.

Genetic studies with animals can be useful due to the high reproduction rate of some species and the ease of experiment with non-human beings, but they pose ethical problems and the results obtained are often impossible to generalize to people.

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How is it different from personality psychology?

In contrast to differential psychology, which is primarily quantitative in nature, the psychology of personality focuses its efforts on the causes, characteristics and consequences for the behavior of variability interindividual.

On the other hand, the psychology of individual differences does not only analyze personality, but is also interested in other aspects, such as intelligence, socioeconomic variables and certain patterns of behavior, for example criminal behavior.

Regarding the methodology, differential psychology is based to a greater extent on studies that delimit the relative influence of heredity and environment on determined variables. In contrast, personality psychology uses mostly correlational and clinical methods. Both share an emphasis on experimental methodology.

In any case, the scope of study of these two disciplines frequently overlaps. In the field of temperament and character, personality psychology investigates multiple facets of variations in behavior, while differential psychology quantifies them and also attends to other aspects of nature human.