Psychology of individual differences: what it is and what it studies

The psychology of individual differences studies how people have different ways of behaving and what are the causes for this to be the case.

Its origins date back to classical times, although its constitution as a scientific branch of psychology is given almost at the same time when psychology itself was constituted as a science, drinking much of the notions evolutionists.

Then we will discuss in depth the psychology of individual differences, a fundamental subject in all the faculties of psychology and in the research departments of the sciences of the behavior, and which allows us to understand that no two people are the same, their way of being a mixture of genes and environmental factors.

• Related article: "The 12 branches (or fields) of Psychology"

What is the psychology of individual differences?

The psychology of individual differences is the discipline that is responsible for studying why people are different from each other. People are the same as long as we belong to the same species, however, it is also indisputable that no two people are the same, not even those who are identical twin brothers. Each person has characteristics that differentiate them from the rest, making them unique and unrepeatable individuals.

Individual differences are those differences that give each one of us individuality. They distinguish us and differentiate us from the rest in various behavioral aspects, such as temperament, level of intelligence, propensity to suffer from mental disorders and other aspects associated with the unique personality of the individual, all of them and their differences object of study of differential psychology which, in fact, is part of the psychology of personality.

In essence, we can say that the psychology of individual differences aims to describe, predict and explain interindividual (between people), intergroup (between groups) and intra-individual (of the same person throughout his life) in relevant psychological areas, also focusing on what are the origin, manifestation and functioning of such variability.

Relationship with general psychology

Often the psychology of individual differences is contrasted with general psychology, whose object of study is rather antagonistic. It is not that differential and general psychology are at odds in theoretical terms, in fact, their fields study and knowledge are complemented by giving us greater knowledge about behavior human. General psychology is responsible for studying what all human beings have in common, what psychological aspects define us as a species as a whole.

General psychology uses an experimental method based on the E-R (stimulus-response) or E-O-R (stimulus-organism-response) paradigm. Instead, the psychology of individual differences mainly uses the correlational method, based on the O-E-R paradigm (organism-stimulus-response or individual-stimulus-behavior), which was postulated by Louis Leon Thurstone in 1923 taking an approach person-centered scientist, whom he takes as his starting point and relegates the stimulus as a mere momentary circumstance of the environment.

Despite the fact that the O-E-R paradigm is currently the most accepted within differential psychology, it has been the subject of debate many times by various researchers in this field. Among them we can find the Spanish psychologist Antonio Caparrós, who proposed the R-R paradigm, focused on the responses of the individual, their measurement and the relationships between them.

• You may be interested in: "The main theories of personality"

History of this psychological branch

The history of the psychology of individual differences can be divided into two great periods: pre-scientific period or historical background and scientific period or modern period. This last period would come hand in hand with the foundation of psychology as an empirical science and based on the scientific method strictly speaking., an event that occurred during the 19th century.

Prescientific period

Before the founding of psychology as a science and, to its extent, differential psychology, there were a number of knowledge, beliefs and ideas about why people behave in one way or another, either in a "normal" way or in a way pathological. Throughout all of history, human beings have asked ourselves what makes a person nice or unfriendly, more or less intelligent, functional or alienated.

While it is certain that the first humans must have wondered why the members of their tribe were different from each other and those of another tribe too, the first written antecedents on individual differences in the West are found in Greece Classic An example of this is found in the figure of Plato, who tried to elucidate and explain why people we behave differently, exposing it in his work "La República", where these differences are explicitly recognized human-.

In the Middle Ages the subject was also approached from a philosophical perspective. In fact, the scholastic theory taught in the colleges of the time addressed this question. Also It is during the Middle Ages that the Spanish doctor Juan Huarte de San Juan wrote his work "Examination of the Ingenios para las Ciencias", text in which he spoke about intelligence, differences in creativity between people and differences in certain skills based on sex.

The work of Juan Huarte de San Juan has been so important to psychology and especially the psychology of individual differences that this great thinker has ended up becoming the patron of all the faculties of Psychology in Spain, being a holiday on February 23 in its honor. He really is a pseudo-patron, since he is not canonized by the Catholic Church and, ironically, his work was censored by the court of the Holy Inquisition.

Centuries later and well into the Renaissance and the Enlightenment, other great thinkers would speak about individual differences in the Modern Age. Between the 18th and 19th centuries we can find philosophers like Jean-Jacques Rousseau, Johann Heinrich Pestalozzi, Johann Friedrich Herbart and Friedrich Fröbel.

The most modern figure who greatly influenced and helped in the founding of differential psychology as a scientific discipline is the naturalist Charles Darwin, promoter of several advances in science biological. Darwin's studies, which would help him to formulate his well-known theory of evolution, gave special emphasis to individual differences found in individuals of various species and, also, in human beings, whom he had no qualms about considering animals and putting them into his theory evolutionist.

Scientific epoch

Although there have been several psychologists who have been credited with creating the expression "individual differences", one of them being William Stern, several historical records show that Charles Darwin already used them even in his best known work "On the Origin of Species" (1859), besides being one of the first to show scientific interest in the study of individual differences. This interest would be shared by his half-cousin Francis Galton in his attempt to quantify individual differences between people, which is why some consider Galton the founder of differential psychology.

Galton was the first to try to apply the evolutionary principles of variation, selection and adaptation to the study of the human being. He did this by experimentally measuring individual differences in his Anthropometric Laboratory. In his attempt to organize the data he was collecting he introduced the statistical method with elements such as correlation, normal distribution and regression, concepts that would later be refined by Karl Pearson and Irving Fisher.

From general psychology will give rise to many other disciplines, including experimental psychology, interested in formulating general laws that explain human behavior in general. At first, psychology ignored individual differences and these were considered simple random errors. Later, J. McKeen Cattell, an experimental psychologist interested in interindividual and intergroup differences, would publish the first works that ended up redirecting the initial center of interest in such differences, separating the differential psychology from the experimental one progressively.

Throughout the twentieth century the psychology of individual differences would take various impulses, among them the creation and improvement of mental tests, tools that apparently made it possible to objectively measure various human characteristics. The first ones focused on intelligence and personality, having the Cattell personality test and the Binet-Simon intelligence scale. Psychometry would take shape, helping in the maturation of psychological questionnaires thanks to the improvement of reliability and validity techniques.

All these milestones would definitively make differential psychology become independent, this being officially recognized in 1957 at the 65th Annual Convention of the American Psychological Association, whose director Lee Cronbach distinguished the scientific status of psychology from individual differences within the branches of psychology modern.

Between the 1950s and 1970s there was a great diversification in the investigations of individual differences. Differential psychology was losing homogeneity and began to receive numerous criticisms from Clinical and Experimental Psychology. Starting in 1970, there would be a boom in this discipline, with the great impact of the so-called “cognitive revolution”.

• You may be interested in: "History of Psychology: main authors and theories"

Its objective

Like any other branch of psychology, that of individual differences aims to study human behavior. Nevertheless, its more specific objective is to describe and explain interindividual, intraindividual and intergroup differences. In addition, it aims to carry out a functional study of the variability of behavior through a specific methodological approach.

Its main object of study focuses on interindividual differences, which make reference to the fact that at a certain moment or situation different individuals behave in a different. In order to describe this variability in the most adequate way, it is necessary to measure the differences individual through psychometry and tests of personality, intelligence and disorders mental.

Another object of study, not as studied but no less important, are intra-individual differences. That is, it is the study of the different ways of behaving of the same individual, comparing it with itself over time and in reference to a certain variable.

Regarding intergroup differences we refer to when the same psychological characteristic is observed or measured in different individuals. Some of them tend to give answers or get scores on similar tests. Despite all this, group behavior itself does not exist, but rather a generalization according to which the mean of a certain variable of the members of the group differs from the others groups.

Methodology

The method most used by differential psychology is correlational, which compares individuals and groups and is among the methodologies of the "ex post facto", that is, the phenomenon is observed after it has occurred. In most cases, the independent variable is not manipulated, since its manipulation has already taken place naturally before and there is no way to manipulate it. The orientation of the psychology of individual differences is nomothetic, since it studies the shared characteristics between individuals that make up a homogeneous group.

Along with this method, cross-sectional correlation is added, in which representative samples of different populations are compared and it is used to observe intergroup differences; and the longitudinal correlation, which is based on making successive measurements of the same subjects during an indefinite period of time, used to observe intra-individual differences.

Although it is usual to use correlational methods, observational and experimental techniques can also be used, as is the retrospective method, although it does not have much relevance in differential psychology. This methodology is based on the compilation of information using information extracted from the explanations made by the own subjects about their behavior, or using biographical data obtained from other sources, such as the testimony of beings dear.

As for the tools used in this discipline, we find a wide variety. We can find neurophysiological measures including electroencephalography (EEG), magnetic resonance imaging (MRI), positron emission tomography (PET)... These methods can be used to search for biomarkers of biologically based behavioral patterns (temperamental traits and symptoms of psychiatric disorders).

Other methods include behavioral experiments to observe how differently people behave when doing the same task. Behavioral experiments are often used in both personality and social psychology, and includes lexical methods and self-reports in which people are asked to complete questionnaires prepared by psychologists.

Aspects studied

Among the most investigated phenomena in difference psychology is intelligence, studied above all in terms of performance and ability to perform tasks in academia, work and life everyday. Its stability over time is also studied, if it grows or decreases as it goes growing, what factors increase it (Flynn effect), differences between sexes and heritability and influence environmental. In addition, the extremes are addressed, that is, intellectual disability and giftedness.

Although not without controversy, the psychology of individual differences has also addressed the definition of intelligence. Some understand it as something more or less homogeneous, while others speak of multiple intelligences. What does coincide is in the unit used to measure this construct, speaking of IQ and accepting its distribution following the normal curve in the population.

Another aspect studied in differential psychology are moods and, above all, personality traits. To understand the personality it is very important to consider the variations in temperament, which constitutes the basic nucleus of an individual. Currently it is possible to study the structure of this phenomenon thanks to lexical-factorial and biological-factorial models. Another concept closely related to personality is that of character, understood as the motivational disposition of the individual.

The debate in this psychological branch about the origin of individual differences is now classic. Although an attempt has been made to use a scientific explanation for this, in its origin there were two positions extremists, one arguing that it was all due to genetics, and therefore human differences were hereditary; and another who defended that everything was due to the environment, the differences being influenced by the environment. This debate has been called “nature vs. nurture ", that is, “nature vs. breeding".

Over time an agreement was reached and today it is accepted that our way of being, our personality, intelligence and the appearance of mental disorders are due to both factors. It is indisputable that there must be some genetic load that explains our personality but, also, the environment has to exert some influence, especially if it is take into account the countless experiments with monozygotic (identical) twins who when raised separately have behaviors in common and some behaviors different.

Thus, the main debate in the psychology of individual differences has been resolved by establishing that there is an interaction between the genotype of the person and his environment, which gives rise to a particular phenotype, that is, the traits that end up manifesting in the person. In fact, as a result of this internal debate on the psychology of differences, the constitution of disciplines that exclusively study the weight of the environment and inheritance in the way of being of people, as is the case of Genetics Quantitative

Applications of this branch

The Psychology of Individual Differences has a wide application in the field of industrial and organizational psychology, which specializes in human behavior in the workplace. Organizational psychologists often consult with companies and look for ways to improve productivity and morale. They investigate aspects such as the differences between workers who are happy and productive and those who are not so happy and seem unmotivated about their job.

Some individual difference psychologists study human behavior based on biological differences. This type of research explores aspects such as heritability, physical traits and reactions to drugs. Biological differences between individuals may be the key to understanding why people behave and respond in a way different when taking the same medication, allowing the selection of drugs that are more effective according to which patients who present a genotype concrete.

Bibliographic references:

• Eysenck, Michael W (1994). Individual Differences: Normal and Abnormal. Hillsdale, NJ: L. Erlbaum Associates
• Maltby, J.; Day, L. & Macaskill, A. (2007). Personality, Individual Differences and Intelligence. London: Pearson Education.
• Buss, D.M. & Greiling, H. (1999). Adaptive Individual Differences. Journal of Personality. 67 (2): 209–243. CiteSeerX 10.1.1.387.3246. doi: 10.1111 / 1467-6494.00053.
• Chamorro-Premuzic, T. & Furnham, A. (2006). Intellectual competence and the intelligent personality: A third way in differential psychology. Review of General Psychology. 10 (3): 251–267. doi: 10.1037 / 1089-2680.10.3.251. S2CID 146278640.