Several experiments by psychologists and human factors researchers have shown that when young children execute pointing tasks, they perform at levels below older children and adults. However, these experiments were not conducted with the purpose of providing guidelines for the design of graphical user interfaces. To address this need, we conducted a study to gain a better understanding of 4 and 5 year-old children's use of mice. We compared the performance of thirteen 4 year-olds, thirteen 5 year-olds and thirteen young adults in point-and-click tasks. As expected, we found age had a significant
effect on accuracy, target reentry and Fitts' law's index of performance. We also found that target size had a significant effect on accuracy and target reentry. Measuring movement time at four different times (first entering target, last entering target, pressing button, releasing button) yielded the result tha Fitts' law models children well only for the first time they enter the target. Another interesting result was that using the adjusted index of difficulty (IDe) in Fitts' law calculations yielded lower linear regression correlation coefficients than using the unadjusted index of difficulty (ID). These results provide valuable guidelines for the design of graphical user interfaces for young children, in particular when it comes to sizing visual targets. They also suggest designers should adopt strategies to accommodate users with varying levels of skill. (UMIACS-2003-42) (HCIL-2003-16)