Psychology Textbooks Boundless Psychology Sensation and Perception Introduction to Sensation
Psychology Textbooks Boundless Psychology Sensation and Perception
Psychology Textbooks Boundless Psychology
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Psychology
Concept Version 10
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Sensory Difference Thresholds

The minimum amount of change in sensory stimulation needed to recognize that a change has occurred is known as the just-noticeable difference.

Learning Objective

  • Define the just-noticeable difference (JND) in terms of sensory stimuli

Key Points

    • The just-noticeable difference (JND) is the smallest detectable difference between a starting and a secondary level of sensory stimulus. This is the difference in the level of the stimulus needed for a person to recognize that a change has occurred.
    • The absolute threshold is the lowest level at which a stimulus can be detected. This is the point in which an odor is finally sensed, or a sound finally heard.
    • The recognition threshold is the level at which a stimulus can not only be detected but also recognized. This is the point where we recognize a certain smell as smoke, or a sound as an alarm.
    • The terminal threshold is the level beyond which a stimulus is no longer detected. This is the point where the sensory stimulus is so strong the sensory receptors no longer detect the stimulus.

Terms

  • sensory receptor

    A sensory nerve ending that recognizes a stimulus in the internal or external environment of an organism.

  • absolute threshold

    The lowest level at which a stimulus can be detected 50% of the time.

Full Text

Just-Noticeable Difference

The just-noticeable difference (JND), also known as the difference limen or differential threshold, is the smallest detectable difference between a starting and secondary level of sensory stimulus. In other words, it is the difference in the level of the stimulus needed for a person to recognize that a change has occurred.

Turning Up the Volume

The difference threshold is the amount of stimulus change needed to recognize that a change has occurred. If someone changes the volume of a speaker, the difference threshold is the amount it has to be changed in order for listeners to notice a difference.

Influencing the Just-Noticeable Difference

The JND is usually a fixed proportion of the reference sensory level. For example, consider holding a five-pound weight (the reference level), and then having a one pound weight added. This increase in weight is significant in comparison to the reference level (a 20% increase in weight). However, if you hold a fifty pound weight (the new reference level), you would not be likely to notice a difference if one pound is added. This is because the difference in the amount of additional weight from the reference level is not significantly greater (2% increase in weight) than the reference level.

The absolute threshold is the minimum volume of the radio we would need in order to notice that it was turned on at all. However, determining the just-noticeable difference, the amount of change needed in order to notice that the radio has become louder, depends on how much the volume has changed in comparison to where it started. It's possible to turn the volume up only slightly, making the difference in volume undetectable. This is similar to adding only one pound of weight when you're holding 50 pounds.

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