Reinforcement of position preference by automatic intravenous injections of glucose.

Abstract

Hungry white rats were restrained and a 27 gauge needle inserted in the caudal vein. Photoelectric cells controlled a flow of liquid into the vein as long as the rat''s head was in that position, either to left or right of center, which initially occurred with the smaller total duration. Relative preference for this position was increased by glucose but not by saline.