Investigation on relation between index of difficulty in Fitts' law and device screen sizes

Abstract

It is well-known as Fitts' law that the time for a user to point a target on a GUI screen can be modeled as a linear function of "index of difficulty (ID)". The authors investigate whether the ID formulation is appropriate independently of device screen sizes. Result of our experiment revealed that the ID formulation may not consistently capture actual difficulty: users' pointing performances were not consistent among pointing target variations of which index of difficulty are consistent. The term A/W may not be appropriate because the term causes the observed inconsistency. © 2009 Springer Berlin Heidelberg.