Successive reductions of liquid and solid sucrose rewards

Abstract

Successive reductions in sucrose rewards are examined in two analogous runway experiments. In Experiment 1, rats were trained for 24 preshift days with 1 ml of either 30% or 3% sucrose solution as reward. Training trials were administered two per day with an intertrial interval (ITI) of 3-5 min. During 2 postshift days, all animals received 20 trials (10 per day with the same ITI) with the 3% reward. Experiment 2 employed essentially the same procedure, except the rewards were either eight or two Noyes sucrose (92.4%) pellets in preshift. Postshift was to the two-pellet reward. The data suggested a successive negative contrast effect (SuNCE) in Experiment 2 with solid pellets, but not in Experiment 1 with liquid solutions. The findings are briefly considered in light of the sequential and frustration accounts of the SuNCE.