Dear Sambit,

JND is a perception threshold in consumer behaviour. If your change is above the threshold, consumers will recognize it. If not, they will probably don't spot the change at all. I have added a nice video by Gail Tom describing this concept with a lot of examples.

Best regards, Viktor

https://www.youtube.com/watch?v=Upu1rpBV2K0

JND is the Minimal difference that can be detected between two similar stimuli.The j.n.d. between two stimuli is not an absolute amount but an amount relative to the intensity of the first stimulus.The stronger the initial stimulus, the greater the additional intensity needed for the second stimulus to be perceived as different.

Marketers need to determine the relevant j.n.d. for their products

so that negative changes are not readily noticeable to the public

so that product improvements are very apparent to consumers

I believe that applying this psychophysical concept (in which realm it is precise and operational) may be somewhat spurious in the area of consumer perception and behaviour. Even leaving aside the considerable arena of preconscious perception effects (i.e. below the limen), Viktor observes, above, that consumers probably won't notice if a change is below threshold. However, this takes no account of the transmission of information through a consumer population - while most may not notice a small change (e.g. substituting rape seed oil for sunflower seed oil in potato chips, offering considerable savings) if a small number do notice, and feel it is a decrement in quality, they do not simply respond by changing their own behaviour (changing brand) but some will also tell friends, who, so primed, will also then notice and tell their friends...etc. This 'meme model' suggests that small changes (bad or good), if perceptible by at least some consumers, may sweep to full awareness by an entire population over a period of time. 

'You can feel some of the people all of the time, and all of the people some of the time...' but it's a dangerous game to underestimate the wisdom of the crowd.

Thanks Leslie, it is a very good point. 

I have tried to simulate the changes below and above average JND on a social network and the findings support Leslie's argument.

Article Rethinking the Concept of Just Noticeable Difference in Onli...

RG scholars.

Good inputs but not my cup of tea.

Many brands have used it to their advantage by increasing the price without having the consumer notice. Similarly, when they reduce quantity in an offering, a marketer can avoid negative feedback from the customers if they are unable to trace the difference.