Wize University Psychology Textbook > Sensation & Perception
Thresholds, Just-Noticeable-Difference, & Weber's Law
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Thresholds, Just-Noticeable Difference, & Weber's Law
Absolute Threshold - the weakest stimulus that a person can detect 50% of the time.
Just-Noticeable Difference (JND) - the smallest amount that something has to change in order for the difference to be detected 50% of the time. Also known as a difference threshold.
Weber's Law - the size of the JND is a constant proportion to the original stimulus magnitude.
Example: If you can just detect the difference between a 10lb and 11lb weight, you will just be able to detect the difference between a 100lb and 110lb weight. The original stimulus is 10x heavier, so the difference needed is 10x as much.
Practice: Thresholds, Just-Noticeable Difference, and Weber's Law
Which difference would be easiest to perceive?