Ice creams are served in a round tub and juices are served in tall slim glasses. Is there anything fuzzy about it?. Yes, indeed as a consumer we feel we were served more. If you want to test it, go ahead and pour the same amount of juice in standard measuring water bottle – you will get know how much you were actually served. A consumer normally don’t know differences when they are subtle. Though, they identify the differences when they are salient and extreme.


Pic 1: Do we really notice these things during purchase? Source:

Ernst Heinrich Weber a psychologist of 17th century studied how people differentiate between the same stimuli in two different occasions. Imagine you are now lifting  2 pounds of chocolate in your hand and then if you lift a 2.1 pounds of chocolate in the second occasion. Will you feel the difference?.

According to Weber’s Just Noticeable Difference,  the difference between the first and second weight should around 8 – 10 % to make it feel different. Hence, the second time weight is expected to be around 2.16 – 2.20 pounds to make you feel heavy.

This principle of Weber’s law is called as “Just Noticeable Difference(JND)“. Steuart Henderson Britt (1975) wrote an article on how Weber’s law can be used in marketing. Steuart states, Weber’s principle can be applied in improving packaging, product and promotion. Also, he says if the initial stimulus is stronger it requires greater intensity in resulting stimulus to create a difference. To understand it better, if a company wants to be different from the competitors, they need to put more effort in creating such difference. For example, taste of Dr.Peppers is completely different from Coca-Cola but the colour is still the same. Hence, Dr.Peppers wanted it perceive as a Cola product but created difference in the taste to stand out from the competitor. Indeed, Dr.Peppers should have worked a lot on bringing a different taste.

Dairy milk has used Weber’s Law to stay as most fulfilling chocolate among the consumers. In the year 2012, Dairy milk standard bar chocolate weight was reduced from 49 grams to 45 grams and maintained 59 p as price. Price being the major cue in consumer decision-making, people will not normally notice the weight change. The key here is the weight, if the weight was reduced to 39 grams ( based on the findings of Weber – you need 8 -10% change to feel the difference) consumer will find the difference. Cadbury’s cleverly reduced the weight to 45 grams so the consumers will not feel the difference.

Many companies don’t change their logo drastically due to existence of JND element among consumers . When companies change the logos completely they will be looked as a different company as they go beyond the purview of JND.

Look at logo of apple(Pic 2), they have maintained the standards over the years. It is common across all the brands across the globe. History of logos and it changes are completely based on just noticeable difference. Similarly, Coca cola(Pic 3) have not changed their bottle size and colour so far to avoid inconsistency in appealing consumers.


Pic 2: Good use of Weber’s Law  – Source:


Pic 3: Coca Cola’s old and new bottle. Source:

In totality, companies whenever want to share good news to the consumers they project it bigger and salient. If they wish to increase the price or reduce weight of the product they ensure they don’t make it visible to the consumers (See Pic 1) ( Refer: Consumer Behaviour book by Schiffman et al).

Weber’s just noticeable difference is a great foundation to understand how people see differences in weight, light, and sound. It has been explained in terms of marketing by Steuart Henderson Britt ( Article 1, Article 2). Right use of JND will certainly increase the profitability of companies.