Psychology is the science that studies the mind and mental processes. However, these processes are not directly observable by human beings nor are they easily quantifiable. We can observe that a person acts in an extroverted manner, but it is not easy to determine to what degree he is extroverted.

For this reason it has become necessary to design different mechanisms and ways of measuring psychic characteristics. The development of these methods, their application, the analysis of these data and the study of their reliability and validity are the object of psychometry . We will now discuss this area of psychology.

Psychometry as a Measure of the Psyche

Psychometry is understood as the discipline that is in charge of the quantitative measurement of mental processes and abilities .

In this way, a numerical value can be assigned to specific characteristics and events, allowing comparison and contrast with other people or with certain criteria that can serve to establish and verify theories and hypotheses about the functioning of the mind. Thanks to psychometry it is possible to quantify and operationalize the psychic , having largely allowed the development of psychology as a science.

As the mind is something not directly observable, it is necessary to use elements that can indicate the aspect to be treated and the degree in which it is possessed, using observable indicators such as behavior or the recording of physiological activity.

Broadly speaking, we can say that psychometry employs statistical calculation and analysis of results in order to acquire information regarding a given construct (which speaks about some psychological aspect) through a measurement element that it has previously created.

What does it encompass?

As we have seen, psychometry is the branch of psychology that measures concrete aspects of the mind. This involves, on the one hand, establishing a theory that can link mental characteristics with measurable elements, on the other hand, the creation of measurement scales, and finally it involves the development of mechanisms and instruments that allow such measurement.

The creation of the theory

With respect to the first aspect, psychometry establishes the possibility of measuring non-observable constructs from elements that can serve to indicate them, as characteristics of the behaviour. It also elaborates and establishes how they can be observed and from different data it tries to establish what these indicators can be.

The scales

The creation of scales or scaling is another of the basic elements that psychometry takes care of. These scales allow assigning concrete values to the analysed variables , so that they can be made operational and worked with. The aim is to make a specific variable quantifiable.

The measuring instruments

The third and last of these aspects is the creation, on the basis of the scales previously drawn up in order to quantify a specific variable, of instruments that allow this measurement.

Clear examples of these are the psychological tests . In this preparation, we must bear in mind that it is necessary to seek objectivity, consistency, and the capacity to discriminate between subjects, and that they must be valid and reliable.

Some relevant concepts

As a discipline that allows the measurement of the unobservable from the observable, psychometry has to take into account different concepts in order to make the measurement correct and representative. Some of the most relevant concepts are the following.

1. Correlation

The concept of correlation refers to the existence of some kind of link between two variables , which makes changes in one of them coincide with variations in the second one, although this does not ensure that the relationship is one of cause and consequence.

2. Variance and standard deviation

Variance is the degree to which test scores or scores for the same variable can be scattered . The standard deviation refers to how widely scores are expected to disperse relative to the average.

3. Reliability

Reliability refers to the degree to which an item or element used in the measurement of a characteristic does not produce errors , obtaining results consisting of different measurements of the same characteristic in the same subject and context.

4. Validity

Validity is understood as the degree to which the element we are using to measure is measuring what we want to measure . There are different types of validity, such as construct validity, content validity or ecological validity.

A little history

The history of psychology is closely linked to that of measuring the characteristics and capacities of individuals. Psychology as a science would not appear until the creation of the first psychology laboratory at the hands of Wilhelm Wundt, who would begin to carry out experiments in which he tried to measure reaction times and would take into account the subjective aspects through the method of introspection .

However, it is considered that the birth of psychometry dates back to the mid-nineteenth century, when Francis Galton would begin to work on establishing mechanisms to measure the existence of individual differences between individuals.

Galton would employ mechanisms focused on the measurement of physiological elements, his studies being limited to basic processes. But thanks to his studies, fundamental concepts in psychometry emerged such as the principles of correlation between variables and regression , which would eventually be formalised by Karl Pearson, his student.

The first psychological tests

Cattell first came up with the concept of mental test, applying it to the measurement of sensory abilities, but it was not until Alfred Binet that scales for measuring intellectual abilities began to be developed. Binet, together with his assistant Theodore Simon, created the first intelligence scale based on functional criteria .

Later, over time, various types of scales would be made, some of which were even used in the army (such as Army Alpha and Army Beta, used to classify soldiers according to their level of intelligence). Later on an attempt would be made to take into account the presence of possible cultural biases in order to correctly analyse mental capacity.

Spearman would interpret Pearson’s correlation , indicating that the presence of a correlation between variables evidences the presence of a common element. Based on this, he would end up generating his theory on the G factor of intelligence.

Further developments

Some of the main authors who allowed the development of psychometry were mainly those quoted Galton, Binet, Pearson and Spearman, although many other authors would have a key role in this discipline.

Spearman would elaborate the classical theory of tests according to which the scores obtained in the tests should be compared with the reference group in order to be able to give them a meaning, although this limits their reliability and validity by being able to change the results according to those with whom the comparison is made.

Over time, other theories would emerge, such as the theory of item response , which would try to combat this limitation by proposing the test as a way of measuring a subject’s level in a given trait by interpreting it on the basis of statistical probability. Over time, other tests would emerge, such as aptitude or personality tests.

Some applications and usefulness of psychometry

Psychometry is a discipline of special importance for psychology, since it allows us to operate the different mental processes and to make measurements, set criteria, establish comparisons and even develop explanatory and predictive models. In addition, it allows to relate variables and help to establish the existence of relationships between them.

This is necessary in many different areas , such as the following.

1. Clinical Psychology

The various psychological assessment tests and measures are of great importance in clinical practice. Being able to make measurements regarding characteristics or mental states allows us to visualize and get an idea of the state and seriousness of the subject , as well as to prioritize certain aspects during treatment according to the characteristics of the patient.

2. Neuropsychology

Psychological and neuropsychological tests and assessments give us clues as to how a subject’s mental abilities stand in comparison with an established criterion, the population average or his own state in previous measurements.

3. Development evaluation

Throughout our life cycle we develop our capabilities in a certain way. The presence of alterations in this development can be detected thanks to various procedures developed through psychometry, allowing for the anticipation and treatment of dysfunctional elements that make it difficult for the person to adapt to the environment.

4. Evaluation of capacities

Personality characteristics, abilities and skills are some of the many elements whose measurability has emerged from instruments developed through psychometry.

5. Human resources

Determining an individual’s ability to cope with a given job is not easy. Hiring or not hiring an individual must take into account his/her level of ability and his/her mental state in order to allow detecting the level of adaptation to the job and the company.

This assessment is carried out through interviews with the candidates, as well as through psychometric tests that reflect their level of ability in different aspects.

6. Research

Psychology is a science that advances continuously. Research is an essential element in order to achieve a better understanding of the psyche and reality. Establishing relationships between different situations and/or stimuli and/or generating data that can be contrasted are key aspects in this process, for which psychometry is essential as it is the basis for the creation of measurement methods.

On the other hand, psychometrics implies a discussion on the extent to which the way in which the hypotheses are operationalized in measurement tools and concrete variables is reasonable or not, and what are the epistemological limits of doing it that way.

Methodological problems

Psychometry does not provide us with tools that allow us to capture a totally objective image of the psychological predispositions of the subjects studied. There are many limitations linked to psychometric methods and tools.

For example, a frequent problem is the fact that the context in which psychological tests are passed affects the way in which the subjects studied behave . Something as simple as antipathy or dislike towards someone who passes an assessment tool can bias the results obtained, as can nerves when faced with the need to do something that one is not used to (filling in several pages with tests that measure intelligence, for example).

On the other hand, those personality tests that are based on self-reporting do not exactly measure patterns of behaviour that characterise those personality patterns, but rather the way in which individuals see themselves. In other words, between what one wants to study and the data obtained there is a filter of introspection: one must stop to think about one’s actions, and offer an interpretation of them. This is not ideal, although if we assume that most of the subjects studied tend to respond in an honest way, it may help to get closer to their personality, their habits, etc.

Bibliographic references:

  • Borsboom, D. (2005). Measuring the Mind: Conceptual Issues in Contemporary Psychometrics. Cambridge: Cambridge University Press.
  • Beriot, D. and Exiga, A. (1970). Les tests en procès: les abus de la psychotechnique, Paris, Dunod Actualité.
  • Embretson, S.E., and Reise, S.P. (2000). Item Response Theory for Psychologists. Mahwah, NJ: Erlbaum.
  • Humphreys, L.G. (1987). Psychometrics considerations in the evaluation of intraspecies differences in intelligence. Behav Brain Sci. 10 (4): 668-669.
  • Kaplan, R.M., and Saccuzzo, D.P. (2010). Psychological Testing: Principles, Applications, and Issues. (8th edition). Belmont, CA: Wadsworth, Cengage Learning.
  • Michell, J. (1997). Quantitative science and the definition of measurement in psychology. British Journal of Psychology. 88 (3): 355–383.