The impact of acoustical secondary reinforcement during shape discrimination learning of dwarf goats ( Capra hircus)

Abstract

The use of secondary reinforcement is widely accepted to support operant learning in animals. In farm animals, however, the efficacy of secondary reinforcement has up to now been studied systematically only in horses (“clicker training”), and the results are controversial. We investigated the impact of acoustical secondary reinforcement on voluntary, self-controlled visual discrimination learning of two-dimensional shapes in group-housed dwarf goats ( Capra hircus). Learning tests were conducted applying a computer-controlled learning device that was integrated in the animals’ home pen. Shapes were presented on a TFT-screen using a four-choice design. Drinking water was used as primary reinforcement. In the control group (G control, n = 5) animals received only primary reinforcement, whereas in the sound group (G sound, n = 6) animals got additional acoustical secondary reinforcement. Testing recall of shapes which had been successfully learned by the goats 6 weeks earlier (T1), we found a weak impact of secondary reinforcement on daily learning success ( P = 0.07), but not on the number of trials the animals needed to reach the learning criterion (trials to criterion, n.s.). Results in T1 indicated that dwarf goats did not instantly recall previously learned shapes, but, re-learned within 250–450 trials. When learning a set of new shapes (T2), there was a strong influence of secondary reinforcement on daily learning success and on trials to criterion. Animals in G sound reached the learning criterion earlier ( P < 0.05) and needed fewer trials (1320 versus 3700; P < 0.01), compared to animals in G control. Results suggest that acoustical secondary reinforcement supports visual discrimination learning of dwarf goats, especially when the task is new and the salience of S + is low.