Figure 2. Humans’ average reaction time to recognize and respond to a target location as a function of the time between cue and target. A symbolic cue preceded the target and predicted the target’s location. Targets were likely to be in the predicted location (valid cues), unlikely to be in the predicted location (invalid cues) or were randomly predicted (neutral cues). Reaction times depended on cue validity and on the time between cue and target. See Figure 1 and related text in Posner, Nissen, and Ogden (1978) for additional details.