[The behavioral phenomenon of "parasitism" in rats].

29 male Wistar rats had been individually trained pressing the bar and receiving the rewards in the box with the feeder-cup and the bar attached to the opposite walls. Constant pairs of rats were formed. Behavior of rats in pairs was observed during 100 sessions in the same box. As a rule, one of the rats performed most of the bar pressings ("a worker") while its partner received the rewards without "working" ("a parasite"). It was possible to classify rats in four groups by their behavior, i. e. "parasites", "working", rats which changed their behavior from "working" for "parasitic" type and vice versa in the course of the experiment, and rats from the pairs where both partners extinguished bar pressing reflex near to zero level. Correlation was shown between behavioral type of rats in paired experiment and individual typological characteristics of fear reaction to different stimuli. Tests of open field behaviour, reaction of choice between the burrow and illuminated area, and emotional resonance were used for testing fear reaction.