A New Test of Throughput Invariance in Fitts’ Law: Role of the Intercept and of Jensen’s Inequality

Abstract

Fitts’ law states that movement time varies linearly with the index of difficulty or, equivalently, that throughput ( TP) is conserved across variations of the speed/accuracy strategy. Replicating a recent study by MacKenzie and Isokoski (2008), we tested the throughput invariance hypothesis with some fresh data and found the TP to be systematically affected by the strategy. This result, we suggest, pleads against the currently popular definition of the TP inherited from Fitts (1954), namely TP = ID/MT, which we recall is incompatible with the Shannon equation of Fitts’ law. We also show that the statistical elaboration of the TP suffers from a problematic amount of uncontrolled variability due to the multiple inadvertent impact of Jensen’s inequality.

Contributors

Halla B. Olafsdottir

Yves Guiard

Olivier Rioul

Simon T. Perrault

Conference

Publication date: September 2012

Publication date (Print): September 2012

Pages: 119-126

Affiliations

Institut Mines-Telecom

Telecom ParisTech

CNRS LTCI

CNRS LTCI

Institut Mines-Telecom

Telecom ParisTech

Article

DOI: 10.14236/ewic/HCI2012.17

Copyright statement: © Halla B. Olafsdottir et al. Published by BCS Learning and Development Ltd. The 26th BCS Conference on Human Computer Interaction, Birmingham, UK

License:

This work is licensed under a Creative Commons Attribution 4.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

Conference name: The 26th BCS Conference on Human Computer Interaction

Conference acronym: HCI

Conference number: 26

Conference location: Birmingham, UK

Conference date: 12 - 14 September 2012

Conference sponsor: Electronic Workshops in Computing (eWiC)

Conference theme: Human Computer Interaction

Product

Product Information: 1477-9358BCS Learning & Development

Self URI (article page): https://www.scienceopen.com/hosted-document?doi=10.14236/ewic/HCI2012.17

Self URI (journal page): https://ewic.bcs.org/

Categories

Series title: Electronic Workshops in Computing