Winter and Flataker2 have recently demonstrated an impairment in performance of a learned rope-climbing task in rats that have been intraperitoneally injected with either plasma or serum from schizophrenic patients. Rats injected with plasma from control subjects or with saline did not show this effect. Since rope climbing is a relatively complex performance which can be broken down (at least logically) into a number of different tasks, we decided to test the hypothesis that at least part of the effect observed by these authors was a function of a decrease in the activity levels of the experimentally injected animals. That this might have been an important factor in the effect observed is also indicated by Winter and Flataker’s comments concerning activity levels of animals. Normal-plasma-injected animals “usually show nothing abnormal in their behavior, except sometimes some sluggishness while climbing.” Schizophrenic-plasma-injected animals, on the