A technique that measures the impact of command selection on task time and errors is described. Users were timed while performing a drawing task, then while performing the same task with interpolated command selections. The difference between these times, consisting of both the time to select the command and to resume drawing, is the time cost of command selection. Several interface configurations were evaluated with this method including selected combinations of single mouse, two mice, voice and touch. Touch and voice input resulted in faster command selection times (approximately 1 sec) than any of the mouse conditions (approximately 3 sec).

The effect of video display unit presentation rate on reading performance was investigated. Reading material was presented at one of the following presentation-rates: 15, 30, 120, 960 cps, or “instant”. In the instant condition, the full text appeared simultaneously on the screen. In the other conditions, text appeared one character at a time starting in the upper left corner of the screen, from left to right and top to bottom. Reading comprehension was highest under the 30 cps and instant presentation conditions. Total time to perform the reading task was equivalent for all conditions except the 15 cps rate which required a longer time to complete the task. In terms of comprehension and time to perform the task, a slow rate of 15 cps, contrary to previous recommendations, is not desirable for novice computer users.

Videotex systems are two-way communnication systems intended to give users access to large amounts of stored information from their homes and offices. These systems link computer databases to modified television sets over the telephone network. A central computer is used as a large information storage device, monitoring requests for information from several users at one time, finding and sending the information to the person who requested it.