The activity of rats in a swimming situation as a function of water temperature.

Previous research has shown that time before drowning in rats decreases gradually as stress is increased by varying water temperature in the swimming situation. In the present research, the activity of swimming rats appeared to be a U function of varying water temperature, lending support to the notion that activity is a behavioral measure that estimates the rats chances of survival in the water. This conclusion was further supported by the covariation of activity with a different behavioral measure of survival. In addition, activity during sessions decreased gradually, suggesting that a lowered activity is an adaptive response in the rat. Activity, thus, appears to be negatively correlated to the rat's survival chances under colder (14-23 degrees) and warmer (23-47 degrees) temperatures; i.e., in a more stressful situation, including extreme fear. It may be, therefore, that a decrease in activity obtained in present laboratory models (i.e., immobility) is more relevant to the extinction of fear than despair, as reported by other researchers.