4.3 Difference Thresholds: The Just-Noticeable Difference

What is a just-noticeable difference, and what factors influence our ability to detect the difference between two stimuli.

just noticeable difference aka difference threshold

the minimum change in a stimulus required for an observer to detect a difference 50% of the time

Weber’s law

says that the difference threshold is proportional to the change in stimulus, usually perceived sort of like a percentage of difference

ΔI/I

• Δ = minimum change needed to detect a difference (JND)

• I = original stimulus intensity

• The ratio is constant for a given sense, but varies across senses.

weber’s law vs JND

weber’s law says that the difference is based off of the percent change from the initial stimuli where as JND says that you just have to add a certain amount then you will notice
ex. if it started small and there was a small change, it would be more noticeable compared to having it start big then having a small change

applicability of weber’s law

through the equation, the percentage is applicable to other scenarios similar