User`s guide

E-Prime User’s Guide

Appendix D: Display Presentation

Page A-53

The figure below illustrates the three basic steps involved in the perception of a stimulus on a

computer screen. The inset graphs show the time course over a 100ms period. The first step is

writing the stimulus to the video memory. A display command in the source code of an

experiment instructs the program to write information to the memory on the video controller card.

The second step is actually putting the stimulus on the screen, which occurs in scanning or

“refreshing” the screen. This cycle will be explained in detail below, but note now that it is the

limiting factor in how fast a stimulus can be put on the screen. The third step is activating the

subject’s retina. Let’s consider each of these steps in turn.

Figure 1. Steps involved in the perception of a stimulus displayed using a

computer.