difference threshold

The smallest difference between two stimuli that can be noticed 50% of the time.

Just Noticeable Difference (JND)

The minimal difference that be detected between two similar stimuli is called the differential threshold, or just noticeable difference.

In the field of psychophysics, that branch of experimental psychology that studies sensation and perception, a jnd is the amount that something must be changed for the difference to be noticeable, defined to mean that the change is detectable half the time

just noticeable difference

Ccasc