JND vs Difference Threshold

What is the difference threshold (or Just Noticeable Difference – JND)?

A: The smallest change in a stimulus that a person can detect 50% of the time.

Q: Are the difference threshold and JND the same thing?

A: Yes — they both describe the minimum detectable difference between two stimuli.

(“Difference threshold” is the concept; “JND” is the amount of change measured.)

Q: Example of a JND:

A: If you can barely tell that a 10 lb weight is heavier than a 9 lb one, the 1 lb difference is your JND.