The effects of shifts in the rate of presentation of repetitive neutral events (background event rate) were studied in a visual vigilance task. Four groups of subjects experienced either a high (21 events/min) or a low (6 events/min) event rate for 20 min and then experienced either the same or the alternate event rate for an additional 40 min. The temporal occurrence of critical target signals was identical for all groups, irrespective of event rate. The density of critical signals was 12 signals/20 min. By the end of the session, shifts in event rate were associated with changes in performance which resembled contrast effects found in other experimental situations in which shift paradigms were used. Relative to constant event rate control conditions, a shift from a low to a high event rate depressed the probability of signal detections, while a shift in the opposite direction enhanced the probability of signal detections.

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During t,he previous two meetings of this organization, I have attempted to emphasize the group as a vehicle for understanding and treat'nient of the chronic.ally ill child. Specifically, I have noted t.he contributions that. can be made by group psychotherapy with mothers of asthmatic children toward the understanding of family processes, helping the mot'her to face and accept relevant emotional factors, and insuring that the patient receives optimum benefit from his hospital and post-hospital experience. The second major focus was eniphasizing the per~onal interaction bet.ween hospital staff and patient, as well as staff aiid st,aff, and even patient and patient. A child in such a milieu is recognized a s the responsible and actively participating member of the treatment community. H e is urged to socialize, react, rebel, and identify rather than to expect ctrtain protective and sedative measures which often encourage dependency and regression. There is, therefore, a predictabilit'y and I hope joy-