Psychophysics: The Beginnings Of Psychology

The origin of Psychology did not appear with hypnosis, but with the works of Fechner and Weber.

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 that encountered various difficulties to emerge. 

And it is that although the human mind has interested man since ancient times, it was not until 1879 when  Wilhelm Wundt 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.

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 the perception of a subject 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 sensation and the evaluation that were made of it entered into analysis. The measurement of psychophysical aspects required highly precise instruments and the elaboration of different techniques that would allow the obtaining of valid and reliable data, being in fact psychophysics 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 investigation of mental phenomena. In other words, it measures the behavioral response to 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 by themselves.

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

The fathers of psychophysics

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

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

These experiments were expanded and deepened by Fechner, who would elaborate the Weber-Fechner law and analyze phenomena such as the absolute threshold or the minimum 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

The investigations of Weber, and later the investigations of Fechner, allowed to formulate one of the first psychophysical laws. Specifically, it is established that we can differentiate between different stimuli based on the intensity with which they are presented. We distinguish between relative changes: we may not grasp the difference between two different stimuli that occur at the same time unless there is a specific change in their intensity. 

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 ability to discern requires that said intensity increase be constant, based on the value of the variation with respect to the starting point.

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

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

Original methodology

The methods used during the first moments of psychophysics were indirect when 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 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 whether he is able to perceive the stimulus or whether a comparing 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, it can generate errors based on the expectation that the stimulus increases or decreases in intensity and the perception is biased.

Constant stimuli method

This methodology of classical psychophysics is based on the use of predetermined intensities that remain constant, but contrary to the method of limits, the intensity of the stimulus varies randomly. It is usually the most used method since it allows minimizing 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 to carry out direct measurements of the sensation, creating estimation scales centered on the subject’s own subjective sensation and their way of assessing said perception. The methods proposed by Stevens, which later are those 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. Method of estimating ratios

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

3. Method of production of reasons

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

4. Method for estimating quantities

In the estimation of magnitudes, the experimenter presents to the examinee a series of stimuli that the subject must value numerically, presenting an example so that he has a rough idea of ​​the value of a sample of the stimulation.

5. Method of production of quantities

This methodology is based on the explored subject 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 come to fruition, which in turn allowed the generation of scales and methodologies that allow much more cognitive and abstract aspects to be measured based on performance in tasks related to these 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, JJ (2012). Basic Psychology. CEDE Preparation Manual PIR, 08. CEDE: Madrid.
  • Goldstein, EB (2006). Sensation and Perception. 6th edition. Debate: Madrid.
  • Fontes, S. and Fontes AI (1994). Theoretical considerations on the psychophysical laws. Rev. de Psicol. Gral. And Aplic., 47 (4), 191-195. National University of Distance Education (UNED).

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