Acquired equivalence of cues in learning a matching-to-sample task by rats

Two experiments were conducted to examine the question of whether stimulus classes between stimuli formed at reaching to criterion in a matching-to-sa mple discrimination had two properties of stimulus equivalence relation in rats: symmetry and transitivity. In Experiment 1, two thirds of the rats we re trained to associate both a particular sample (CONV) with one of compari sons (H) and another particular sample (D) with the other comparison (V) to criterion, or were overtrained. Then they were given two backward associat ion tasks. The remaining rats received a pseudo matching-to-sample discrimi nation training in Phase 1, but were given the same training as the other r ats in Phase 2. The rats trained with the matching-to-sample discrimination learned the shift problem faster than the rats trained with the pseudo mat ching-to-sample discrimination. Overtrained rats learned backward associati ons faster than non-overtrained ones. In Experiment 2, rats were trained to associate a particular comparison stimulus (C) with either of two sample s timuli (Con or Cr). Then they were trained to associate a new comparison (V ) with one of the samples (Con). Rats required to choose the new comparison (V) when sample stimulus (Cr) was presented mastered a subsequent task fas ter than those required to choose the other comparison (H). These results o f two experiments suggest that rats can satisfy criteria of symmetry and tr ansitivity for the demonstration of equivalence relation between stimuli.