EFFECTS OF REINFORCER TYPE ON RATS SENSITIVITY TO VARIATION IN REINFORCER AMOUNT AND REINFORCER DELAY

Twenty rats, divided into two groups, served as subjects in an experim ent that examined choices between reinforcers that varied in amount or delay. One group received food reinforcers, and the other water reinf orcers. No difference was found between the two groups in their values of s(A) (tendency of choice behavior to vary in accordance with varia tion in reinforcer amount). However, Group Food had significantly lowe r values of s, (tendency of choice behavior to vary in accordance with variation in reinforcer delay) than did Group Water, and Group Food's values of s(A)/s(A) (a measure related to self-control-choices of lar ger, more delayed over smaller, less delayed reinforcers) tended to be greater than for Group Water. Finally, over the session, s, and s(A)/ s(D) showed no significant change, overall response rates decreased, a nd s, increased. Taken together, these s results suggest that, indepen dent of deprivation level, self-control for water is less than self-co ntrol for food. (C) 1997 Elsevier Science B.V.