Abstract
The three most common variations of Fitts’ index of difficulty are the Fitts formulation, the Welford formulation, and the Shannon formulation. A recent paper by Hoffmann [1] critiqued the three and concluded that the Fitts and Welford formulations are valid and that the Shannon formulation is invalid. In this paper, we challenge Hoffmann’s position regarding the Shannon formulation. It is argued that the issue of validity vs. invalidity is ill-conceived, given that Fitts’ law is a “model by analogy” with no basis in human motor control. The relevant questions are of utility: Does a model work? How well? Is it useful? Where alternative formulations exist, they may be critiqued and compared for strengths and weaknesses, but validity is an irrelevant construct. In a reanalysis of data from Fitts’ law experiments, models built using the Shannon formulation are (re)affirmed to be as good as, and generally better than, those built using the Fitts or Welford formulation.
Highlights
Scientists pursue their research using a body of techniques known as the scientific method
In Fitts’ analogy, movement amplitudes are like signals and target tolerances or widths are like noise
It is important to remember that the benefit in using the effective target width is not because it produces a model with higher correlations, but, rather, it brings accuracy into Fitts’ law, and makes it a true speed-accuracy model of human motor behavior
Summary
Scientists pursue their research using a body of techniques known as the scientific method. We examine Hoffmann’s claim that the Shannon formulation for Fitts’ index of difficulty is invalid, and that the Fitts and Welford formulations are valid. We provide background discussion on Fitts’ law, emphasising issues relevant to Hoffmann’s analysis and the contrary points developed . We present and critique the analysis developed by Hoffmann on the validity and invalidity of the formulations. The third section examines the empirical evidence Hoffmann offers in reanalysing published data. While such analyses are common and often provide insight, they are irrelevant on the question of validity vs invalidity for alternative formulations of Fitts’ index of difficulty. The analysis reaffirms the utility of the Shannon formulation for Fitts’ index of difficulty
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
