title: Generalization decrement and not overshadowing by associative competition among pairs of landmarks in a navigation task.
abstract: When they are trained in a Morris water maze to find a hidden platform, whose location is defined by a number of equally spaced visual landmarks round the circumference of the pool, rats are equally able to find the platform when tested with any two of the landmarks (Prados, & Trobalon, 1998; Rodrigo, Chamizo, McLaren, & Mackintosh, 1997). This suggests that none of the landmarks was completely overshadowed by any of the others. In Experiment 1 one pair of groups was trained with four equally salient visual landmarks spaced at equal intervals around the edge of the pool, while a second pair was trained with two landmarks only, either relatively close to or far from the hidden platform. After extensive training, both male and female rats showed a reciprocal overshadowing effect: on a test with two landmarks only (either close to or far from the platform), rats trained with four landmarks spent less time in the platform quadrant than those trained with only two. Experiment 2 showed that animals trained with two landmarks and then tested with four also performed worse on test than those trained and tested with two landmarks only. This suggests that generalization decrement, rather than associative competition, provides a sufficient explanation for the overshadowing observed in Experiment 1. Experiment 3 provided a within-experiment replication of the results of Experiments 1 and 2. Finally, Experiment 4 showed that rats trained with a configuration of two landmarks learn their identity.
authors: Department of Basic Psychology, Institute for Brain, Cognition and Behavior, University of Barcelona, Passeig de la Vall d'Hebron 171, 08035-Barcelona, Spain. victoria.diez.chamizo@ub.edu
authors: Victoria D
authors: VD
authors: Chamizo
authors: Clara A
authors: CA
authors: Rodríguez
authors: Alfredo
authors: A
authors: Espinet
authors: N J
authors: NJ
authors: Mackintosh
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D003463:Cues; D004192:Discrimination, Psychological / Q000502:physiology; D004924:Escape Reaction; D005260:Female; D005793:Generalization, Psychological / Q000502:physiology*; D008297:Male; D018782:Maze Learning; D010775:Photic Stimulation; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time; D012737:Sex Factors; D013028:Space Perception / Q000502:physiology*; D013037:Spatial Behavior / Q000502:physiology*; D013649:Taste / Q000502:physiology; D013997:Time Factors