Differential Psychology

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The Differential Psychology (rarely Differential Psychology ) deals with the differences between individuals in terms of psychological characteristics and conditions. Exact descriptions, tests and measurements provide the basis for the subsequent research: How do these differences develop from genetic predispositions and social influences? How are these characteristics related to each other and how can they be classified? How do these characteristics change under different living conditions and to what extent are they due to education, psychotherapy, medication, etc. a. Measures to influence?

In the course of study in psychology , differential psychology and personality psychology together form the subject of differential and personality psychology (personality research).


In the beginning, the differences in sensory performance, reaction speed and intelligence functions and the like were of particular interest. a. Skills as well as in relatively persistent personality traits . The approach then broadened because most of the characteristics were not found to be constant. Personality traits can change over time. People differ in terms of short- and medium-term constancy of certain characteristics and the extent of long-term plasticity, for example introversion and extraversion in youth and old age. The short-term changes in status, such as performance or well-being during the day, are also unmistakable. In this respect, too, there are striking differences between people. Consequently, differential psychology must deal with:

  • Differences between the individual persons (inter-individual),
  • Differences (variability) within a person (intra-individually) and
  • Differences between people in terms of their variability (inter-individual differences in intra-individual variability ).

Differential psychology deals with all psychological characteristics of human experience and behavior and, depending on the question, also refers to the underlying physiological and neurophysiological differences as well as information and the like. a. about socio-psychological, socio-economic, ecological aspects. (Amelang et al. 2006; Asendorpf 2007). (see biopsychology , heritability , individuality , constitution , psychophysiology )

With its precise descriptions and methodological principles, differential psychology provides the scientific basis for many other areas of psychology, especially psychological diagnostics and applied psychology .


Sir Francis Galton (1822–1911) with his Inquiries into Human Faculty and its Development (1883) and James McKeen Cattell (1860–1944) are among the pioneers in this field of research . Both examined numerous functions in many people, especially psychophysiological characteristics such as sensory performance and reaction times. James McKeen Cattell wrote the book Mental tests and measurement (1890) and introduced the term test into psychology. Around 1891 Hugo Münsterberg developed exercises on verbal associations, arithmetic, reading and memory. By Hermann Ebbinghaus (1897) the idea of recording tasks sentence completion in meaningful texts in the tests originated.

The French psychologist Alfred Binet (1857–1911), together with Théodore Simon, created a series of exercises to measure the mental performance of school children; it was the first intelligence test . The systematics and the research program of differential psychology were first developed by the German psychologist William Stern (1871-1938). Raymond B. Cattell (1905–1998) expanded this methodology, especially through the statistical method of factor analysis , and through his extensive work on a universal index of personality factors (Cattell 1957).

William Stern's Differential Psychology (1911) contains the first systematic program in this field of research. According to Stern, characteristics are everything "that is present in the individual as empirically determinable" (Stern 1911, p. 20). He founded differential psychology by delimiting this view from general psychology : what is considered uninteresting variability or measurement error in general psychology becomes the subject of differential psychology.

“Until recently, almost all endeavors in scientific psychology had one thing in common: they gripped problems in general. (…) Such an abstraction is justified as long as it arises from an insight into the temporary limits of our ability; but the danger is that one forgets to have an abstraction in front of you (...). After all, the researcher encountered psychological peculiarities everywhere, even against his will; and if this was initially only a source of error for his generalized view, then it ended up being similar to other cases in the history of science: the source of the error itself became a problem. "

In addition, Stern calls the "special psychology", which deals with the investigation of selected subpopulations (including women, men, occupational groups). Both research directions are looking for generally applicable laws and presuppose that people are nevertheless comparable in their differences - due to “general characteristics” (cf. common traits according to Allport 1937). In addition to "differential psychology in the narrower sense", Stern defines another question and follows the scientific methodical distinction between the process of nomothetics and idiography , i.e. H. the search for general laws or the understanding of individual characteristics (see personality). Stern describes the individual-centered view:

“Here, too, the investigation is still nomothetic; but the closer the group is, the more specific the type, the essence of which is to be determined, the closer it is to the limit of this research direction. The impact of the particular on the general becomes stronger and stronger, and the limit is reached where the individual individuality itself becomes a problem. Because individuality always means singularity. Every individual is a structure that is nowhere and never in an identical form. Certain regularities are confirmed in it, certain types are embodied in it, it is comparable in many respects with other individuals - but it does not go completely into these regularities, types and equations, there always remains a plus that sets it apart from others Differentiates between individuals who are subject to the same laws and types. Thus individuality is the asymptote of science which seeks laws. (…) If it is indeed the sole task of science, as some science theorists want it to be, to find universally valid, then there is no psychology of the individual individuality. ”(Stern 1911, p. 4).


Research on intelligence , along with psychophysics, is the area in which the methodology of psychological measurement was mainly developed. This is where the modern psychological test methods and the theory of psychological tests originated. The possibilities and limits of these methods are still controversial, because there are fundamental differences between these methods, which are often based on subjective assessments, and those used in physics and the like. a. Natural science typical objective measurement . (see psychometry , scaling ).

In intelligence research it also becomes clear that differential psychology is not satisfied with the test methodical description, but asks how the observed differences come about: How much can be explained by hereditary disposition or by upbringing ? What other conditions promote or hinder intelligence performance? Differential psychology also asks how the individual characteristics are related to one another. The statistical method of correlation is often used for this. The magnitude of the correlation coefficient expresses how closely two characteristics are related, and nothing can be said about what causes this relationship or which variable controls the other. Further questions are: Is the intelligence performance related? a. with creativity or with certain personality traits , and to what extent the test results make it practical to predict other differences, e.g. B. in school success and professional success?

William Stern already distinguished four main approaches to differential psychology: Variation research is aimed at comparing one characteristic in many individuals; the correlation research examines two or more features to many individuals; the psychographics considered an individual with respect to many features; the Komparationsforschung compares two or more individuals regarding many characteristics. Since then, these strategies have been methodologically differentiated and (with the exception of psychography, see biography ) supplemented by suitable statistical methods. Raymond B. Cattell (1957) in particular took the important step of differentiating the concept of the psychological characteristic by distinguishing between observation and measurement opportunities in space and time, i.e. different situations and points in time, and defining appropriate correlation techniques. (Amelang et al. 2006; Stemmler 1992)

From these approaches of differential psychology, the methodology of psychological tests and observation methods emerged , the scientific quality of which is assessed according to certain quality criteria . (see psychological diagnostics ).

  • the content validity ( validity ) of a test value: how well it represents the property meant?
  • the formal reliability ( reliability ): How exactly can a test value be reproduced by a second measurement of this type?
  • the temporal constancy ( stability ): how exactly can the test values ​​be reproduced in the short and long term?
  • the internal consistency : how closely are different individual features of the intended property related?
  • the ability to generalize (generalizability): how well can conclusions be drawn from the test value - obtained in a certain (artificial) investigation situation - about the general expression of this property in everyday life or in other life situations (external validity, ecological validity)?

In addition to the test methodology, the concepts and methods of differential methodology include general investigation strategies, including many that are elaborated as methodologically demanding procedures in research statistics. (Amelang and Schmidt-Atzert 2006; Bortz and Döring 2006).

Feature areas and taxonomy

The differential psychology work program includes all psychological characteristics. Their diversity and the different investigation methods are among the reasons why there is no convincing classification system, no taxonomy of psychological characteristics. Even more important is the lack of a unified theory of personality from which suitable principles of order can be derived. Therefore, only rough classifications are possible, some of which are determined by the functional areas and some by the examination methods:

  • sensory and motor skills, reaction behavior,
  • Intelligence functions, creativity, cognitive performance, special talents, language,
  • Learning ability, behavioral habits,
  • Social behavior, communication style, helpfulness,
  • Temperament characteristics such as basic mood, emotionality, aggressiveness,
  • Basic needs, motives, conflicts, life satisfaction, plans and goals,
  • Modes of experience, changes in consciousness,
  • Self-concepts, d. H. the assessment of one's own person, appearance and talent from various points of view,
  • social and political attitudes, interests, value orientations, ideological (religious) convictions,
  • State of mind (alertness, mood, body perceptions),
  • physical characteristics, psychophysiological and neuropsychological variables.

Individual differences are to be described according to certain aspects, e.g. B. according to age differences, according to gender differences, according to sociocultural differences or with regard to temporal differences in variability (in the course of the day and year, according to longer-term trends and secular changes) as well as comparatively as the relative variability of certain characteristics and characteristic areas.

Idiographic Approaches

Differential psychological research has largely remained a research on correlation and variation. In contrast, biographical personality research developed into a largely independent field of work (see biography , biography research ). The individual-centered view called for by psychologists such as William Stern , Gordon Allport , and Hans Thomae means a great methodological challenge: to describe individual characteristics in such a way that a comparison between people remains possible. For this, a mediating way must be found between the general test and measurement methods, which cannot grasp the individual, and partly empathetic, partly interpretive methods that approximately explore what is special about a person. (see idiography , individuality , interpretation , interview , nomothetics , understanding )

One approach could be the profiles (patterns) of properties characteristic of individuals or the procedures in which the investigated bring in their own psychological experiences and terms, for example in the role construct test (repertory grid test) by George A. Kelly . The term ipsative measurement , in contrast to the usual measurement, means that there is no generally valid scaling , but is only judged for the person and within the own experience, for example by a percentage and comparative estimate of how strong a certain interest or a certain motivation is compared to the other currently experienced interests. However, such individual- centered measurements can only be compared between people with great reservations. Therefore, these methods are more suitable for capturing psychological changes within a person over time.

Research directions

Research on intelligence and other cognitive functions continues to be important directions in differential psychology, also with a view to the neuroscientific foundations. These examinations often lead to the development of new tests and other examination procedures and to standardize them internationally. Innovative methods such as computer-aided data collection in everyday life have opened up new research areas, for example the emotions that occur during the day, stress reactions or physical complaints ( outpatient assessment ). There are numerous tasks in the areas of ergonomics , clinical psychology , educational psychology , which are significantly supported by differential psychology, especially personality psychology and psychological diagnostics .

See also


  • Manfred Amelang, Lothar Schmidt-Atzert: Psychological diagnostics and intervention. 4th edition. Jumper. Berlin 2006, ISBN 978-3-540-28507-6
  • Jens B. Asendorpf and Franz Neyer: Psychology of Personality , 5th, completely revised. Ed., Berlin: Springer, 2012, ISBN 978-3-642-30263-3 .
  • Jürgen Bortz, Nicola Döring: Research methods and evaluation for human and social scientists. 4th edition. Springer, Heidelberg 2006, ISBN 3-540-33305-3
  • Raymond B. Cattell: Personality and motivation: Structure and measurement . World Book, New York 1957
  • Werner Deutsch (Ed.): About the hidden topicality of William Stern . Lang Publishing House. Frankfurt a. M. 1991, ISBN 3-631-43397-2
  • Jochen Fahrenberg, Michael Myrtek: Psychophysiology in the laboratory, clinic and everyday life . Lang Publishing House. Frankfurt a. M. 2005, ISBN 3-631-54229-1
  • Kurt Pawlik, Manfred Amelang (Ed.): Differential Psychology and Personality Research . Encyclopedia of Psychology. Subject area C, Series 8 (4 volumes). Hogrefe, Göttingen 1995-2000, ISBN 3-8017-0533-1
  • William Stern: The differential psychology in its methodological foundations. Huber. Bern 1900–1994, ISBN 3-456-82532-3
  • William Stern: General Psychology on a Personalist Basis . 2nd Edition. Nijhoff, The Hague 1950
  • Gerhard Stemmler : Differential psychophysiology: Persons in situations . Springer, Heidelberg 1992, ISBN 3-540-54800-9
  • Gerhard Stemmler , Dirk Hagemann, Manfred Amelang, Frank M. Spinath : Differential Psychology and Personality Research. 8th edition. Kohlhammer, Stuttgart 2016, ISBN 978-3-17-025721-4
  • Hans Thomae: The individual and his world: a personality theory . Hogrefe, Göttingen 1968
  • Hannelore Weber , Thomas Rammsayer (Hrsg.): Handbook of personality psychology and differential psychology . Hogrefe, Göttingen 2005, ISBN 3-8017-1855-7
  • Hannelore Weber ; Thomas Rammsayer: Differential Psychology - Personality Research. Hogrefe, Göttingen u. a. 2012, ISBN 978-3-8017-2172-5