Probe recognition tasks have shown the effects of sleep deprivation following a full night of sleep loss. The current study investigated shorter durations of deprivation by testing 11 subjects for accuracy and response time every 2 hr. from 10 p.m. through 8 a.m. We replicated Elkin and Murray's auditory single-probe recognition task using the number triplets and added two visual tasks with number and shape triplets. Series of six stimuli were each followed by a probe, which was presented after 2.5 sec. as a short delay or 20 sec. as a long delay. Accuracy performance showed a significant decrease for the long delay beginning after 4 a.m. for the two visual tasks. Response times were significantly slower for the visual shapes task using the short delay. Visual tasks, especially shapes, may be more prone to disruption by sleep deprivation, given the visual information load and the briefness of iconic memory.