The Neural Control of Visually Guided Eye Movements
D. Temporal Factors in Visually Guided Saccadic Eye Movements
          1. The conditions under which express saccades can and cannot be generated.

f. Are express saccades made to familiar targets appearing unexpectedly at new locations and to unfamiliar targets appearing at expected locations?

The top panel of Figure 35 shows the distribution of saccadic latencies to familiar locations using familiar targets. The second panel shows the distribution of saccadic latencies to familiar targets that unexpectedly appear at new, previously not used locations. Such locations were presented infrequently and were randomly interspersed with the presentation of targets at familiar locations. Few express saccades were made to the familiar targets appearing at new locations. The third panel shows the distribution obtained when targets with new colors, shapes or sizes were used that appeared unexpectedly at familiar, expected locations. Many express saccades were made. Thus express saccades are rare to targets that appear at new, unexpected locations but are common when at familiar sites targets with new colors, shapes and sizes appear.