Sensory Thresholds: How they Define our Perception

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

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Human beings, although we are members of the same species and resemble each other in many aspects, we also have great individual differences with each other. Sensory thresholds play a fundamental role in these differences, since they deal with the limits that each person has to tolerate a given stimulus.
In this article we will review what this concept is 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, taking into account the intensity needed to notice it and to make it annoying, among other parameters.

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

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

Its limits

Let’s see what happens when the thresholds of a person are in any of the limits, whether it is the upper limit (greater tolerance to the stimulus) or the lower limit (lower tolerance to the stimulus).

1. Terminal threshold or upper limit

It refers to the breaking point between tolerance and intolerance. After this point any increase in stimulation has an unbearable effect for the subject, which will inevitably have to give in its 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 stimulus level would go unnoticed by the person, since he would not be able to perceive it.

In any of these assumptions, a series of factors that may be biological or even related to social circumstances, the upbringing of the subject, and the environment in which it operates daily, interfere.

This supposes that in no person there are thresholds of absolute sensation, that is, they are not permanent, but 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 be given so that the subject is aware of the difference in one of every two occasions, that is, 50% of the time.

On the other hand, the differential threshold is greater the greater the magnitude of the stimulus. For example, adding 15 grams to one of two objects that weigh 50 grams can make you notice the difference in weight between the two, but if you add them to one of two objects that weigh 5 kilograms, you will not notice the difference, since the differential threshold is higher in this second 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 absolute value, which is known as the minimum threshold, leaving aside other relevant aspects on how the sensations are perceived by the subject.

2. The modern theory of signal detection

Regarding this theory, there is an important variation compared to the previous one, since the threshold is not taken into account. Emphasis is placed on the detection of the signal, regardless of whether the subject realizes or not that he is receiving a stimulus.

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

Methods used to detect the stimulus

When investigating about this field, the following methods are usually used.

1. Limits method

It consists of determining, using the approximate calculation, the point that can be closer to the absolute threshold that you want to find.

2. Method of constant stimuli

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

3. Average error method

In this case it should be the evaluator or the evaluated subject himself who manipulates the intensity of the stimuli he receives, until a significant sensation change occurs.