In a simplified way, we can define User Centred Design (UCD) as the practice of designing products in such a way that their users can use it with minimum stress and maximum efficiency (after a definition by Woodson*). At the end it is the name that has been receiving in the last years what in the U.S. is known as Human Factors Engineering and in Europe is called Ergonomics.

Nevertheless, this change of name comes from something more than a unification of criteria. In the last few years the customer has become the centre of attention of all the operations of a company. The above mentioned definition involves all the departments that take part in one way or another in the launching of a product. It’s not only a set of techniques, but a philosophy of how to do the work.

Jeffrey Rubin describes the three main principles of UCD in his interesting book Introduction to Usability Testing as:

1. An early focus on the users and the tasks they will have to perform with the product. This is done through the structured, and systematic compilation of objective data about the user and the way it will interact with the product.
   
2. Empirical Measurement of Product Usage. The emphasis is placed on the performance of usability tests from the very beginning of the design stage. These tests are based on early prototypes of the product.
   
3. Iterative Design, by the cyclic repetition of the design, parameter modification and usability test phases, from the very beginning and iterating the cycle until a satisfactory result is obtained.

Clearly this is a philosophy, like Total Quality Management or Innovation Management that involves the whole company and is interdisciplinary by nature, since a product must be usable, but also attractive, it must solve a market need and should have a low cost…

Anyone that has launched a product taking into account from the beginning the needs of the user and the usability of the product knows all too well the serious difficulties that it poses:

• On one hand the gathering of reliable data in an objective way, avoiding that our prejudices on what the product should be, prevent us from seeing what the user really needs.
  
• On the other hand, the complexity that the correlation has between the design parameters of the product and the subjective expression of the user regarding his or her satisfaction with the product. This is especially difficult in products like spectacle lenses, in which comfort is expressed with vague words, like "they don’t fit me well" or "I can’t see very clearly".

For this reason we can’t approach UCD in a naive way. It’s not only a matter of asking the user. For years the most serious companies have been using ergonomics in the design of chairs or working places, the Software Engineering has developed methodologies to create (relatively) easy to use user interfaces. In the same way the web development is beginning to show an increasing interest for the UCD, beyond the mere final usability test, performed once the structure and main features of the web are already in place.

A good starting point in order to find relevant information is IBM’s site on UCD. Raïssa Katz-Haas’ article on User Centred Design  is also worth taking a look.

The experience with the latest products in whose development I’ve taken part shows that UCD pays back amply the effort of changing the mentality, integrating with other departments and overcoming the difficulties of interpretation and statistical evaluation of the user response. The products obtained this way go clearly beyond what could be expected by using traditional methods

*Woodson, Wesley E. "Human Factors Design Handbook", 1981 McGraw-Hill

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