When monkeys interrupt their saccadic scanning of a visual scene to lo
ok at a suddenly appearing target, saccades to the target are made aft
er an ''express'' latency or after a longer ''regular'' latency. The p
urpose of this study was to analyze the spatial patterns of scanning,
express, and regular saccades, Scanning patterns were spatially biased
, Express saccade patterns were biased, too, and mere directly correla
ted with scanning patterns, Regular saccade patterns were more uniform
and were not directly correlated with scanning patterns, Express sacc
ades, but not regular saccades, seemed to be facilitated by preparatio
n to scan. This study contributes to a general understanding of how mo
nkeys examine scenes containing both unchanging and suddenly appearing
stimuli, (C) 1997 Elsevier Science Ltd.