Three experiments are described which elaborate some of the conditions under which rats will contact and manipulate a periodically presented retractable lever. Experiment 1 demonstrated that (i) initial manipulative oral and manual contact with the lever was facilitated if the rat had previous experience of food delivery in the experimental chamber; (ii) persistence in contacting the lever on s...

Twelve rats were food-deprived to 90% or 70% of their free-feeding weights. Food pellets were then delivered every 60 s (Fixed Time 60-s schedule), and the development of adjunctive drinking was measured by the water consumed and the number of licks. For "master" rats, each lick was followed by 10-s delays in food delivery. Yoked control rats received food at the same time as their master rats ...