Central Tendency

In 80’s, the advertisement of surf detergent become very famous and through the ad they penetrated the market to compete with Nirma detergent. The success of the ad is need to be attributed to the character ‘Lalitaji’.

In the ad there is no mention about who and what is personality type of Lalitaji. But everyone understands that she is a typical middle class housewife and never settle for anything less than what she has paid for. The need for no explanation explains the central tendency principle (in modeling the character).

Also, did you ever questioned yourself why somethings attracts you very much? And you always try to dream about beautiful things though it does not exists in reality. The reason to personify the beauty or consider somethings attractive, is based on the central tendency of a thing.

Let see more about the central tendency or averageness. In every day life, we use the ‘average’ in many context. ‘On average, 4 people are…’, ‘What is the average rate..’, etc. Remember, ‘With static form the motion’, is the design motto. The average is the attempt to find the static part i.e. the center of the system. Let me explain with some examples to illustrate the central tendency.

We get attracted to beautiful objects. The reason behind the attractiveness factor is due to the perception of the central tendency of the object. For example, what makes a face beauty? On research they found that the attractive faces are only average, i.e. people liked the face created based on the average of other faces. Here average corresponds to the nose-, ear-, eye-length and size, etc. The average face is more attractive than the individual face. Also people get attracted when there is a peak shift in the averageness.

The above figure shows that how an average face is formed by composite of 30 faces. (More details can be found here). People always like or dream about the average face rather than real face.
Once a person is questioned, why he likes that girl very much. He replied that she looks like the actress ‘abc’. He questioned again, why do you like that actress? He answered that the actress face is similar to his girl friend’s face. Actually the person does not like the girl and the actress, but a image which is average of both. He dreams about that image and in reality he likes both the persons.

This concept was applied in ancient Indian art too. For example, to design a statue of God, they use the aspect of ‘averageness’ and an amplification factor. To design the Goddess Parvati which supposed to represent the very epitome of feminine sensuality, grace, poise, dignity, everything that’s good about being a woman, all they need to apply is averageness principle. How does the artist convey the very epitome of feminine sensuality? What he does is, simply take the average female form, subtract the average male form – you’re going to get big breasts, big hips and a narrow waist. And then amplify it, amplify the difference. Thus comes the statue of goddess.

Suppose a dog comes to you and request you to create a God statue for them. Then all you need to do is to study physique of that dog’s group and find the averageness and amplify the important characteristics to get the God statue for the dog. But it is tricky, we can’t come up with single God statue as there can be various types of dogs, so in that case just localize your task for each type of dogs and you get different god statues.
Now let me put in a formal way from the design aspect. Basically two things are done – collect the user data and model users based up on that. The former one is all about the contextual inquiry (which was discussed in the post ‘The Understanding‘) and the latter is called Persona. Personas are fictitious characters that are created to represent the different user types within a targeted demographic who might use a site or product. Lalitaji of Surf is an example of persona. If you want to develop any product, you need to come up with personas based on the user’s contextual interview. Then try to come up with scenarios (how user behaves) before designing the product. Usually in the software development, it is not done, rather they try to design with ‘Use Cases’. But following the process of contextual inquiry and personas is a powerful method to come up with a good design.

Hence the design sutra is, “Understand the users and average the users


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