What is the Difference Between Absolute Threshold and Signal Detection Theory

The main difference between absolute threshold and signal detection theory is that absolute threshold is the lowest level of stimuli an organism can detect at least half the time whereas signal detection theory is a theory that states that detection of a stimuli states that both the intensity of the stimuli and physical/psychological state of the organism.

Different people respond to the same signal (sound, touch, sight, etc.) differently. For example, one person may be able to detect a very low sound, while others are not able to detect this sound. Absolute threshold and signal detection theory are two concepts that explain such situations.

Key Areas Covered

1. What is Absolute Threshold 
     – Definition, Characteristics
2. What is Signal Detection Theory
     – Definition, Characteristics
3. What is the Difference Between Absolute Threshold and Signal Detection Theory
     – Comparison of Key Differences

Key Terms

Absolute Threshold, Signal Detection Theory, Signal, Stimuli

What is Absolute Threshold

Originally, the absolute threshold was defined as the lowest level of stimuli (sound, touch, taste, etc.) an organism could detect. However, some modifications had to be made to this theory after the introduction of signal detection theory. After these modifications, the absolute threshold is considered to be the smallest amount of a stimulus we can detect 50% of the time.

In the hearing, the absolute threshold is the smallest level of a tone that a person with normal hearing can detect, especially when there are no other interfering sounds. Moreover, in vision, the absolute threshold is the smallest level of light a participant can detect. Measuring the absolute threshold in vision may involve measuring the distance at which a person can detect the flame of a candle in the dark.

For smell, the absolute threshold involves the smallest concentration a person is able to smell; for instance, the smallest amount of perfume a person is able to smell in a large room. When considering touch, an absolute threshold is the amount of force that allows you to detect the feeling of something touching your body; as an example, a feather lightly brushing your arm. Besides, it’s important to note that the absolute threshold for touch varies for different body parts as some body parts are more sensitive than others.

Figure 1: Absolute Thresholds of Hearing (by age in males and females)

Furthermore, the absolute threshold may change as we grow old. Younger people are able to detect stimuli at lower levels; as people grow old, they need greater stimulation to detect the same stimulation.  

What is Signal Detection Theory

Signal detection theory is a theory that states that our ability to detect a signal depends not only on the strength of the signal but also on our experience, expectation, motivation, and degree of alertness. For example, the way different people respond to the same signal is different, and even the same person may detect a specific signal at one, but not at another.

Figure 2: Signal Detection Theory

Furthermore, in psychology, signal detection theory is used to measure the way people make decisions under conditions of uncertainty; for example, how a person perceives the road under foggy conditions. According to this theory, the decision-maker does not just passively receive information; he also actively makes difficult perceptual decisions under conditions of uncertainty.  For example, when you are driving under foggy conditions, you have to decide how far away from you an object is, based only on visual stimulus which is impaired by the fog.

Difference Between Absolute Threshold and Signal Detection Theory

Definition

The absolute threshold is the smallest amount of a stimulus we can detect 50% of the time whereas signal detection theory is a theory that states that our ability to detect a signal depends not only on the strength of the signal but also on our physical/psychological state.

Basis

Moreover, the absolute threshold is the minimum stimulus necessary to perceive something 50% of the time while signal detection theory examines how nonsensory factors like attitudes, expectations,  knowledge affect an individual’s perception of stimuli.

Conclusion

Absolute threshold is the lowest level of stimuli an organism can detect at least half the time. Signal detection theory, on the other hand, is a theory that states that detection of a stimuli states that both the intensity of the stimuli and physical/psychological state of the organism. Thus, this is the main difference between absolute threshold and signal detection theory.

Reference:

1. Cherry, Kendra. “What Is Absolute Threshold .” Verywell Mind, Verywell Mind, 23 Jan. 2020, Available here.
2. “Detection Theory.” Wikipedia, Wikimedia Foundation, 18 Apr. 2020, Available here.

Image Courtesy:

1. “Ath-byage” – The original uploader was Tlotoxl at English Wikipedia. – Transferred from en.wikipedia to Commons (CC BY-SA 3.0) via Commons Wikimedia
2. “Signal detection” By Nbeltz – Own work (Public Domain) via Commons Wikimedia