Paper Reading #1: Only One Fitts' Law Formula - Please!

Comments:
Chris Kam
Stuart Jones

Reference Information:
Title: Only One Fitts' Law Formula - Please!
Author: Heiko Drewes
Presentation Venue: CHI 2010 April 10-15, 2010 Atlanta, Georgia, USA

 Summary:
First things first, what is Fitt's law? Fitt's law gives a relation for the mean time to point at a target of given size in a given distance. This is important because pointing is a very frequent action when interacting with a computer using a mouse device.

The problem with Fitt's formula is there are at least four different equations used in the community that do the same thing. There are many publications regarding Fitt's law and they all don't agree on a single formula.

Fitt's law can be derived from a simple model often called the discrete-step model. This model is demonstrated by a pointer that approaches the target in steps. After each step the pointer aims to the target center and reaches a position within an error circle, this is the starting point for the next step. Each steps brings the pointer closer to the target and ends when the pointer reaches the target.

This is a discrete-step model for Fitt's Law

This is only a model and it has problems like all models. It ignores factors which directly influence the pointing actions. Other factor's include the subjects' mood, their nervousness, their eye-sight, chemical substances like alcohol or caffeine in their blood, or distractions from the environment.

A scientific approach must be used to decide which formula to choose. Each of the four formulas is acceptable in the HCI community but each demands good statistical values for its use. This is not the scientific approach.

One possibility is to make HCI an art so all cases are acceptable, but HCI wants to be a science then scientific standards must be discussed.

Discussion:
This was kind of a confusing article. I understand the confusion in having four formulas but there were terms I didn't understand that were thrown around.  One of his statements stuck out in my mind, the author said that Fitt's Law is one of the few HCI formulas used and supports a scientific claim rather than the art of design and sof factors due to human nature. This sounds like people in HCI are not used to viewing things scientifically in this field. I'm sure it's not that simple but that's what it sounds like. So, people are using this formula however they choose and not using it scientifically. I think if there has to be more than one formula then they should have different names. From the author's perspective it sounds like a Highlander scenario where, there can be only one! Therefor, the HCI community wants to be a scientific community it needs to figure out a standard for this formula.