Combined and interacting effects of hand and head movement delays on discrete manual performance in a virtual environment.

Transmission delays occur when a virtual environment responds to the hand and head movements of an operator. The effects of hand and head-related delays on discrete manual performance was investigated experimentally and compared. Imposed hand and head-related pure delays equal to or greater than 110 ms and 220 ms, respectively, significantly increased hand Movement Time (MT). The effect of hand-related delays was greater than that of head-related delays of the same magnitude. A regression model describing the combined effects of both delays on MT is reported (R(2) = 0.95). Analyses of the interactions among delays, target width, and distances have shown the need to adopt the traditional classification of delays into (1) control delay, and (2) display delay. The use of this taxonomy and the regression analyses to describe and explain the effects of individual and combined effects of delays on discrete target-reaching task performance in virtual environments are discussed.