To function effectively, we need absolute thresholds low enough to allow us to detect sights, sounds, textures, tastes, and smells. We also need to detect small differences between the stimuli. A musician must detect the slightest variation when tuning his instrument. And parents must detect the sound of their child’s voice among the voices of other children.
The differential threshold (also called just noticeable difference or dap) is the minimum difference that a person can identify between any two stimuli 50% of the time. The difference threshold increases with the magnitude of the stimulus. So, for example, if you add 10 grams to a 100 gram weight, you will notice the difference; However, if you add 10 grams to a one kilogram weight, you will not notice the difference because the difference threshold has increased.
Fountain: Myers, D. (2006), Psychology 7th edition. Panamericana Medical Editorial.
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