Sensory thresholds: what they are and how they define our perception.

A field studied especially from psychophysics and the measurement of tolerance to stimuli.

Although we humans are members of the same species and are similar in many ways, we also have great individual differences from one another. Sensory thresholds play a fundamental role in these differences, as they are the limits of our tolerance to stimuli.Sensory thresholds play a fundamental role in these differences, since they are the limits that each person has to tolerate a given stimulus.

In this article we will review what this concept is all about and break down the most relevant aspects of it.

What are sensory thresholds?

Sensory thresholds refer to the degree to which a subject reacts to a given stimulus.The intensity necessary to notice it and for it to become annoying, among other parameters, is taken into account.

This is determined through the magnitude that exists between the so-called thresholds, which are composed of minimum thresholds and maximum thresholds. The lower a person's threshold for a specific stimulus, the lower the degree of tolerance to it. The opposite occurs when the tolerance threshold is high; in this case the subject presents a high tolerance to the stimulus, and may even be hyposensitive to it.

It can be understood then that sensory thresholds are basically the margins of our sensations. are basically the margins of our sensations..

Its limits

Let's see what happens when a person's thresholds are at one of the limits, either the upper limit (higher tolerance to the stimulus) or the lower limit (lower tolerance to the stimulus).

Terminal threshold or upper limit

This refers to the tipping point between tolerance and intolerance. After this point any increase in stimulation has an unbearable effect on the subject, who will inevitably have to cease to tolerate the stimulus.The subject will inevitably have to give in to resistance.

2. Absolute threshold or lower limit

This consists of the minimum degree of sensation that must exist for the subject to be able to perceive the stimulus.. A lower intensity in terms of the level of the stimulus would go unnoticed by the person, since he/she would not be able to perceive it.

In any of these assumptions, a series of factors interfere, which may be Biological or even related to social circumstances, the subject's upbringing, and the environment in which he/she develops on a daily basis.

This assumes that there are no absolute sensation thresholds in any person, i.e., they are not permanent, but are subject to change depending on the circumstances in which the subject lives. are subject to change depending on the personal circumstances of each individual..

What is the differential threshold?

The differential threshold is the minimum difference in the intensity of a stimulus that must occur for the subject to become aware of the difference every second time, i.e. 50% of the time.

On the other hand, the differential threshold is higher the greater the magnitude of the stimulus.. For example, adding 15 grams to one of two objects weighing 50 grams can make the difference in weight between them noticeable, but if we add them to one of two objects weighing 5 kilograms, the difference will not be noticed, since the differential threshold is higher in the latter case.

Related theories

These are the main theories of sensory thresholds.

1. The psychophysical theory

This theory has focused most of its research in the field of the absolute value, the same that is known as the minimum threshold, leaving aside other relevant aspects on how sensations are perceived by the subject.

2. The modern theory of signal detection

Concerning this theory, there is an important variation in comparison with the previous one, since the threshold is not taken into account. Emphasis is placed on the detection of the signal, regardless of whether or not the subject is aware that he or she is receiving a stimulus..

This is achieved through sophisticated measuring instruments, which are specially designed to quantify the intensity of a given signal received by the organism, even though it is imperceptible to the subject's consciousness.

Methods used for stimulus detection

The following methods are usually used for research in this area.

1. Boundary method

It consists of determining, using approximate calculation, the point that can be closest to the absolute threshold to be found..

Method of constant stimuli

In this case the subject is subjected to the stimuli in a random manner. That is to say, they are not used in an ascending or descending manner. New stimuli are simply tested constantly, and the results are recorded.

3. Average error method

In this case it should be the evaluator or the evaluated subject him/herself who manipulates the intensity of the stimuli of the stimuli received, until a significant change of sensation is produced.

Bibliographical references:

• Bialek, W. (2012). Biophysics: Searching for Principles. Princeton University Press. p. 40.
• Levine, M. (2000). Fundamentals of Sensation and Perception. London: Oxford University Press.