We studied the extent to which time-on-task is correlated with perception of usability for people who are familiar with a phone model and for those who are not. Our controlled experiment, conducted in Japan, correlated subjective usability assessments with time-on-task for expert and novice users on three different mobile phone models. We found that the correlation between perceived usability and time-on-task is stronger when participants are more familiar with the phone model. While not significant when initially inspecting a new phone model, a negative correlation between time-on-task and perceived usability becomes significant with as little as an hour's time doing tasks on the unfamiliar phone. This suggests that designing the UI to make time-on-task as short as possible may not have much effect on the purchase decision, but as experience increases, it may increase the loyalty of existing users.

We propose a new technology called the camera-typing interface, which can read printed characters such as URLs with a low-resolution camera. It realizes a type of ubiquitous information service using smart phones with cameras. This method includes two main advantages: automatic concatenation of sequential shots and automatic error correction by re-shooting. The automatic concatenation enables a user to take segmented images of a character string, thus a low-resolution camera can be used as the interface device. The automatic error correction enables the user to correct misrecognized characters just by retaking images around them, providing an easy and natural way of error correction. We present two experimental results to prove effectiveness of our method. Both results indicate that our proposed method is helpful.