Slipping and Drifting: Using Older Users to Uncover Pen-Based Target Acquisition Difficulties

Karyn Moffatt and Joanna McGrenere


University of British Columbia, Canada


This paper presents the results of a study to gather information on the underlying causes of pen -based target acquisition difficulty. In order to observe both simple and complex interaction, two tasks (menu and Fitts’ tapping) were used. Thirty-six participants across three age groups (18-54, 54-69, and 70-85) were included to draw out both general shortcomings of targeting, and those difficulties unique to older users. Three primary sources of target acquisition difficulty were identified: slipping off the target, drifting unexpectedly from one menu to the next, and missing a menu selection by selecting the top edge of the item below. Based on these difficulties, we then evolved several designs for improving pen-based target acquisition. An additional finding was that including older users as participants allowed us to uncover pen-interaction deficiencies that we would likely have missed otherwise.

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