What is the effect of position for VDT dynamic/static displays on users' reading comprehension?

The study investigated the effects of position (upper, below, right-hand, and left-hand side of the screen) for VDT dynamic display and other factors including speed (150, 200, 250, and 300 wpm), display type of dynamic information (leading, flash and RSVP),, and polarity combination of dynamic/static(black-on-white/black-on-white, white-on-black/white-on-black, black-onwhite/white-on-black, and white-on-black/black-on-white) on subjects' comprehension for reading static and dynamic display information. The result of this research showed that position and type of dynamic information had no significant effect on subjects' comprehension for dynamic and static information. Polarity combination and speed also had no significant effect on subjects' comprehension for static information; however, the two factors had significant effects on subjects' comprehension for dynamic information. When display speed was set at 200 wpm, subjects' comprehension was better than with at speed settings. When the dynamic/static display was set to be the same polarity combination (black-on-white/black-on-white), subjects' performance was better than other polarity combinations.