Not all methods to create a strong user experience are efficient. Worse still, some are quite the contrary !

Allow me to explain using an analysis of number representation by Denis Guedj (a professor in science history and epistemology at the university Paris VIII-http://en.wikipedia.org/wiki/Denis_Guedj).

## Roman numerals use letters: I, V, L, C, D, M, …

The problem with this method is that for each number that is higher than the previous one, you need to add a new sign. That means that the number of basic signs increases in function of new needs.

## The Indian numeration, which is the basis of our system, allows doing everything using very little.

With only ten numbers, from 0 to 9, you can represent any possible number you want.

This method, which was finalised in the 16th and 17th century by Indian astronomers and mathematicians, is still valid today and has never been challenged by any other method.

## Let’s take an example and write the number 1999

**In Roman numeration, these are the rules to be followed:**

- Use addition to reach the number
- Proceed by power of ten by power of ten (multiples of the decimal)
- If you need to use four symbols, use the subtractive method
- Only use the symbol immediately preceding the symbol when using the subtractive method

By following these rules, we get this result for 1999: M CM XC IX (1000 -100 + 1000 – 10 + 100 – 1 + 10) and not MIM (1000 – 1 + 1000)

**In Indian numeration, instead of having to follow rules, you have to answer the following questions:**

- How many thousands? Answer: 1
- How many hundreds? Answer: 9
- How many tens? Answer: 9
- How many units? Answer: 9

## To me, the world of user experience can be compared to numeral systems:

Usability is a set of techniques that evolve empirically, like Roman numeration. Usability mainly uses the rules of common sense applied to objects.

What is extraordinary is to see how many usability guidelines lists exist that contradict one another.

Usability, like Roman numeration, leaves us with an enormous field of possible subjective interpretations.

The interpretation of the rules concerning Roman numeration allows us to write 1999 in several ways:

**MCMXCIX**(1000 – 100 + 1000 – 10 + 100 – 1 + 10) – Respects the official rules as they were written down in the Middle Ages**MCMXCVIIII**(1000 – 100 + 1000 – 10 + 100 + 5 + 1 + 1 + 1 + 1) – Probably how the Romans wrote it, since the 9 was often written as VIIII**MDCCCCLXXXXVIIII**(1000 + 500 + 100 + 100 +100 + 100 + 50 + 10 + 10 + 10 + 10 + 5 + 1 + 1 + 1 + 1) – Possible because there are four following letters

Behavioural science however is based on the fundamentals of the perceptive and cognitive system of the human brain. If you know these fundamentals, you can answer all possible interaction cases without having to rewrite new rules every time you encounter a new problem. It’s like using the numbers from 0 to 9. What does evolve over time is not the set of rules, but the fundamentals themselves.

That’s why I am convinced usability has been on the decline since 2 years and why UX based on Behavioural Sciences is so rapidly gaining ground. The future will tell 😉

I think I was taught what you call “indian” numeration to be “arabic”. AFAIK, it’s the arabs who came up with “our” current numeration.

Actually MIM would do. 1000 – 1 + 1000.