Finger width corrections in Fitts' law: implications for speed-accuracy research

Area of Science:

• Human-Computer Interaction
• Cognitive Psychology
• Motor Control

Background:

• Fitts' task is a widely used paradigm to study human motor control and performance.
• The standard Fitts' task assumes a point-like probe, but real-world interaction often uses larger probes like the finger pad.
• This discrepancy can introduce systematic errors in performance metrics.

Purpose of the Study:

• To highlight the potential for misleading results when using the finger as a probe in Fitts' tasks.
• To demonstrate the necessity of correcting for finger pad width in calculating the index of difficulty.
• To illustrate the impact of this correction on information processing rate calculations, particularly in developmental contexts.

Main Methods:

• Experimental manipulation of target width and finger pad size.
• Application of Fitts' law with and without target width correction.
• Analysis of information processing rates across different age groups in a developmental study.

Main Results:

• Using the finger pad as a probe significantly increases target tolerance.
• Failure to correct for finger pad width leads to overestimation of information processing rates.
• The magnitude of this overestimation varies with age due to changes in finger pad size.

Conclusions:

• The finger pad width must be incorporated into Fitts' task analysis for accurate performance assessment.
• This correction is particularly important in developmental research where anthropometric measures change.
• Accurate measurement of information processing is vital for understanding motor development and optimizing human-computer interaction.