The differential threshold or just noticeable difference is the minimum increase in a stimulus required to detect a difference in the perception.
There is also a ‘terminal threshold’, which is the magnitude of stimulus at which there is no increase in the perception of stimulus increasing.
What is the differential threshold?
The difference threshold, also known as the just noticeable difference (jnd), is the minimum difference in stimulation that a person can detect 50 per cent of the time. We experience the difference threshold as a just noticeable difference.
For example, let’s say I asked you to put your hand out and in it, I placed a pile of sand. Then, I add tiny amounts of sand to your hand and ask you to tell me when you notice any change in the overall weight.
As soon as you can detect any change in the weight, that difference between the weight of the sand before I added that last bit of sand and the amount of sand after I added it, is the difference threshold.
Understanding Differential Threshold
It is the difference between two stimuli or between one level of a stimulus and another level of that stimulus, where stimulus refers to something that causes a change in an organism.
In the example of the lipstick, the stimulus is sight – the visible colour of the lipstick. The absolute threshold was the amount of colour less than which you would not know she was wearing any. T
he differential threshold for the lipstick could be the difference between the palest of pinks and the deepest of reds.
Or it could be the just noticeable difference between palest pink and pale pink. The differential threshold would also be involved in determining the coverage of two different brands of lipstick.
Say you had one brand that gave you a full rich pink colour and another that gave you just a pale thin pink wash; that’s a differential threshold between two brands of lipstick.
Let’s say he’s considering two different cars to buy. If you offer him a nice family sedan with enough power to move along the highway carrying four kids and a dog, he’s not interested (note that these things all intertwine, we’ve now got both performance and style, but I digress…).
If you offer him a vintage sports car that used to have power but since it got the crack in the engine block won’t go up a hill at anything faster than 40 km (my old MGB), he’s not interested. Let’s say you even offer him another performance car, but not the BMW.
He’s still not interested. Compared to the BMW, these other cars have different levels of performance. He wants a minimum level of performance, yes, and that’s his absolute threshold, but beyond that, he wants what the BMW has to offer, not lower levels of performance. That’s differential thresholds.
What are differential and absolute thresholds?
Absolute threshold is “The lowest level at which an individual can experience a sensation…” (Schiffman and Wisenblit 2015, p. 90).
In other words, an absolute threshold is the point to which one can make the difference between “something” and “nothing” and is considered that person’s absolute threshold to a particular thing or “…stimuli” (Schiffman and Wisenblit 2015, p. 90).
The differential threshold or the just noticeable difference (JND) is “The minimal difference that can be detected between two similar stimuli…” (Schiffman and Wisenblit 2015, p. 91).
Ernst Weber, a scientist, found “…that the JND between two stimuli was not an absolute amount, but an amount relative to the intensity of the first stimulus” (Schiffman and Wisenblit 2015, p. 91).