Four adult pigeons were conditioned to adjust to a preferred ambient temperature and to receive food or water by instrumental responses. The experiments were performed in a Skinner-box under heat load conditions. Each session lasted 1 h. The birds were deprived of food and water for several days before the actual experiments with the exception of the control tests.
The exposure to different heat loads (50°, 55° and 60° C) effected both an increase in the responses for cold reward and a rise in respiratory evaporation (panting). The combined effort of behavioral and autonomous responses resulted in constant body temperature (42° C) under the three heat conditions (Fig. 1).
The food deprivation effected a preference of instrumental response for feeding and a negligence of behavioral temperature regulation, whereby a slight hyperthermia resulted in the first part of heat exposure (55° C, Fig. 2).
Water deprivation reduced the rate of respiration and simultaneously forced the response for cold reward, through which the deep body temperature was adjusted to the control level of 42° C (Fig. 3).
Intragastric infusion of 20 ml NaCl (0.8 mol) half an hour before starting heat load (55° C) produced the same result as water deprivation. Whereas infusion of isoosmotic KCl solution did not produce any deviation from the control tests (Fig. 4).
The results show competition between the conditioned thermal behaviour and the motivation of feeding or drinking in animals which may permit to compare the conditioned thermal behaviour with the natural kinds of behavioral temperature regulation. The non-appearance of hyperthermia under conditions of water deprivation and NaCl loading may indicate that the animals are able to use the autonomous and the behavioral types of heat defence responses to a greater or lesser extent as circumstances demand. This question seems to be of great interest and is fully discussed here.