Which statement about JND is true?

• A. It is the smallest detectable difference between two sensory stimuli
• B. It measures reaction time delays in music
• C. It is unrelated to perception
• D. It defines musical tempo

Answer: (A)

Just noticeable difference, or JND, is the smallest difference between two sensory stimuli that a person can detect. This concept measures how finely our perceptual system can discriminate changes in input, and it underlies the idea that there’s a threshold where a difference becomes noticeable. In music perception, JND helps explain when a change in loudness, pitch, or timing becomes perceptible to listeners, which relates to how we notice subtle shifts in performance or production. It is not about how fast we react to stimuli, nor about defining tempo, and it is fundamentally tied to perception, not unrelated to it. Therefore, the statement that JND is the smallest detectable difference between two sensory stimuli is the correct one.