Effects of pen size on human performance on hand-held devices

This paper shows the effects of stylus-pen size on user performance on hand-held devices such as personal digital assistants. The purpose of this study is to determine the most suitable size (pen-length, pen-tip width and pen-width) for a stylus pen. In this study, the most suitable size is determined on the basis of performance data and user preferences. In Experiment 1, five kinds of pen-lengths (7, 9, 11, 13, 15 cm) were evaluated. In Experiment 2, six combinations of the three kinds of pen-tip widths (0.5, 1.0 and 1.5mm) and the two kinds of pen-tip widths (4 and 7mm) were compared. In both experiments, subjects conducted pointing, dragging and writing tasks on a PDA. The results were assessed in terms of the performance evaluations (completion time, error rate, linear relationship with index of difficulty for pointing and dragging tasks; handwriting character input time, movement time between two boxes, protruding strokes, error correction and recognition rate for handwriting task) and subjective evaluations for all three pointing, dragging and writing tasks). Results showed that the range of required pen dimensions was more than 11cm for pen-length, 0.5mm to 1.0mm for pen-tip width, and 7mm for pen-width.