You are glancing everywhere searching for information on your computer screen. Soon, you start to feel frustrated and lose patience. Suddenly someone come to your rescue. Standing just behind your shoulder, this helper rapidly points out where to look on the screen. You may or may not have experienced it but this story is related to the notion of Useful Field of View (UFOV).
It is the single most important concept in effective screen and web page design. It is at the essence of human attention, a central issue in Cognitive Engineering.
What is it?There is a small area in the retina that provides the clearest vision of all. This vision is also called the central vision or foveal vision. It corresponds to a spot making an angle of 3 degrees. So for someone sitting in front of a computer screen, the size of the spot of visual attention is about 4 cm. For someone standing behind the shoulder of somebody else in front of a computer screen, the size of the spot is about 8 cm. The spot is about 24 cm when watching television at a normal distance. So somebody standing just behind you will have a broader spot than you and will be more likely to find the information your are looking for on the screen.
In the example above, if information is outside the UFOV, it will not be recognise or perceive. Consequently, if you place adds anywhere, they will not be effective because they are likely to be outside the UFOV. Knowing what users are looking is a fantastic insight when combined with the UFOV notion. A designer can suggest new cross-related option (or add) and present them inside the UFOV.
This concept is simple and effective and it explains why Google’s Add is so successful.Why not do the same?