Psychophysics: the beginnings of Psychology

Today it is not strange to hear about psychology as a science or the figure of the psychologist in various fields related to the study of the mind and behavior. However, it is a relatively young scientific discipline and that he encountered various difficulties to arise.

And it is that although the human mind has interested man since ancient times, it was not until 1879 when Wilhelm Wundt he created the first psychology laboratory and psychology was established as a science. At that time and even before it, the beginnings of psychology are linked to the first attempts to measure the relationship between physical and mental aspects; that is, to psychophysics.

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

What is psychophysics?

Psychophysics is understood to be the branch of psychology whose main object of study is the relationship between external stimulation and its qualities and a subject's perception of said stimulation.

It is one of the first types of study that was carried out in a scientific way in which psychological aspects such as the sensation and the evaluation that were made of it entered into analysis.

The measurement of psychophysical aspects required highly precise instruments and the development of different techniques that would allow obtaining valid and reliable data, psychophysics being in fact the direct precursor of psychometry.

In psychophysics, models began to be developed in which a numerical value was assigned to the characteristics of the stimuli and their perception, being a pioneer in the quantitative research of the mental phenomena. In other words, it measures the behavioral response to the physical stimulus. Psychophysics was born at the beginning dedicated to the study of visual perception, but later it will be expanded in such a way that it ended up being extended to the study of the relationship between the physiological and the psychic.

It is assumed that the stimulation generates a physiological activation that ends up causing a sensation, Although both components separately also have the potential to generate sensations on their own themselves.

Psychophysics used different methods to measure sensation. Among them we find the description by the subject of what is perceived, its recognition, detection, the perception of the magnitude or the search for the stimulus.

• Related article: "What is Physiological Psychology?"

The fathers of psychophysics

Although there are precursors in ancient Greece and in numerous philosophers such as Hume, it is considered that the main fathers of psychophysics were Weber and Fechner.

The first of them is especially recognized for his experiments related to the stimulus detection threshold. Weber investigated the dual detection threshold, or the level of separation necessary for a stimulus to be picked up in a fragmented way (he used a compass on the subject's skin, and he analyzed when he noticed a single stimulus and when he was able to discern the two points as stimuli separated.

These experiments were expanded and deepened by Fechner, who would elaborate the Weber-Fechner law and would analyze phenomena such as the absolute threshold o the minimum of stimulation necessary to awaken a sensation and the differential threshold, previously proposed by Weber, in which the difference necessary for them to notice changes in the perception of a stimulus.

Weber's law and Fechner and Stevens reformulations

Weber's research, and later Fechner's research, made it possible to formulate one of the first psychophysical laws. Specifically, it is established that we can differentiate between different stimuli based on intensity with which they present themselves. We distinguish between relative changes: we may not grasp the difference between two different stimuli occurring at the same time unless there is a specific change in the intensity of these.

But if the intensity of the stimulus itself increases, the relative difference will also have to increase to capture the existence of two different perceptions. Thus, this capacity for discernment requires that said increase in intensity be constant, based on the value of the variation with respect to the starting point.

For example, if we touch two raindrops very close together, we may need a small separation to notice two sensations while if what touches us are the jets of a hose the separation between them must be somewhat greater to be perceived as elements different.

This law would be superseded and modified by the reformulations of Fechner and Stevens, which would end up identifying that sometimes an increase in the magnitude of the stimulus does not generate a change proportional in perception but sometimes generates a perceptual change much greater or much less than what expected.

• You may be interested: "Aleksandr Luria: biography of the pioneer of neuropsychology"

Original methodology

The methods used during the first moments of psychophysics were indirect by working from the measurement of the physical stimulus and obtaining the sensation from it. It is considered that the sensation could not be measured directly, being only associated with the magnitude of the stimulus. In this type of psychophysics, three main types of methods stand out.

Limits method

The experimenter presents a series of different stimuli, which will or will not be captured by the subject studied. The experimenter manipulates the intensity of the stimulus, the examinee having to say if he is able to perceive the stimulus or if a comparison stimulus is more, equal or less intense. The stimuli have a continuous increasing or decreasing order, going in series. There may be habituation or expectations.

Average error method

This type of methodology is based on manipulating the stimulus until a change in sensation is generated, adjusting the stimulus based on the subject's response. Although it is comfortable and simple since it is the examinee himself who regulates the stimulation, can generate errors based on the expectation that the stimulus grows or decrease in intensity and perception is skewed.

Constant stimulus method

This methodology of classical psychophysics is based on the use of predetermined intensities that are kept constant, but unlike in the limits method, the intensity of the stimulus varies randomly. It is usually the most used method since it allows to minimize errors and biases, although it generates more fatigue.

Direct methodology

Besides Weber and Fechner, another of the great pioneering authors of psychophysics is Stevens. This author would consider the need for direct measurements of the sensation, creating estimation scales centered on the subject's own subjective sensation and their way of evaluating said perception. The methods proposed by Stevens, which later are the ones that have continued to be used in practice, would be the following

1. Categories method

In a similar way to a Likert-type scale, a series of stimuli are presented to the subject that he must classify according to various categories that are proposed to him.

2. Ratio estimation method

Two stimuli of the same type are presented to the examinee at the same time, the latter having to assess the numerical relationship that exists between them.

3. Production method of reasons

The examinee must generate a stimulus from an initial stimulus and a proportionality relationship that the examiner presents you. For example, the subject has to generate light twice as bright as it is presented.

4. Magnitude estimation method

In estimating magnitudes the experimenter presents to the examinee a series of stimuli that the subject must assess numerically, presenting an example so that you have a rough idea of ​​the value of a stimulation sample.

5. Method of production of quantities

This methodology is based on the subject being explored generating the level of stimulation corresponding to the intensity that the experimenter proposes (for example, the intensity of the sound of the voice).

6. Interval estimation method

In it the subject must estimate the difference between two presented stimuli.

7. Interval production method

This method assumes that the examinee recreates an interval within the stimuli, dividing them into different parts.

Effect on other branches of Psychology

Psychophysics allowed the beginning of the qualitative study of psychological aspects such as perceptions. In the long run, this initiative would allow psychometrics to develop, which in turn allowed the generation of scales and methodologies that allow to measure much more cognitive and abstract aspects from the performance in tasks related to said elements. For example personality traits, skills and attitudes or intelligence.

Some branches that have benefited from the contributions of psychophysics are clinical, occupational or educational psychology. In fact, it can even be applied to elements such as physiological activation caused by fear.

Bibliographic references:

• Higueras, B. and Muñoz, J.J. (2012). Basic Psychology. CEDE Preparation Manual PIR, 08. CEDE: Madrid.

• Goldstein, E.B. (2006). Sensation and Perception. 6th edition. Debate: Madrid.

• Fontes, S. and Fontes A.I. (1994). Theoretical considerations on the psychophysical laws. Rev. of Psicol. Gral. and App., 47 (4), 191-195. National University of Distance Education (UNED).

• University of Barcelona (s.f.) Classical and contemporary psychophysics. [Online]. Available in: http://www.ub.edu/pa1/node/113.