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Differential Psychology: history, objectives and methods

Differential Psychology: history, objectives and methods

February 1, 2023

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. Currently 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 the psychology of personality , a discipline very close in some ways.


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

History of differential psychology

In the middle of the 19th century the monk Gregor Mendel carried out the first genetic studies of which there is evidence. Using peas, Mendel determined the laws of heredity, made advances for the future concept of "gene" and coined the terms "dominant" and "recessive" in relation to the heritability of biological traits.

A few decades later Francis Galton, family member of Charles Darwin , became a pioneer of differential psychology and personality through the development of psychometrics. The student and protege of Francis Galton, the mathematician Karl Pearson, made fundamental contributions in the field of statistics and questioned Mendelian laws.


The rise of behaviorism made the influence of differential psychology decay, which re-emerged in the 1960s and 1970s with the publication of Genetics of behavior, by John Fuller and Bob Thompson. These authors they 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 and environmental influences by studying human behavior and mind.

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

Objectives of this discipline

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


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

Despite the fact that differential psychology is often confused with personality psychology, the branch in question investigates a wide variety of topics: intelligence, self-concept, motivation, health , values, interests ... However, it is true that the contributions of differential psychology to personality and intelligence are better known.

From the beginning, the psychology of individual differences has been applied in educational and professional fields, 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.

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Research Methods

Differential psychology uses mainly statistical methods; thus, we work with large samples of subjects and the data is analyzed from a multivariate approach . In this way, elements of experimental control that allow establishing relationships between variables are introduced. 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, designs with animals and those that study individuals raised in special environments. 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 highlight studies with monozygotic twins , 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.

Animal genetic studies can be useful because of the high reproduction rate of some species and the ease of experimenting 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 the psychology of the personality?

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

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

In terms of methodology, differential psychology is based to a greater extent on studies that delimit the relative influence of inheritance and the environment on certain variables. On the other hand, the psychology of the personality uses mainly correlational and clinical methods. Both share the emphasis on experimental methodology.

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


Lecture 03 Methods in Psychology (February 2023).


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