Most equivalence studies with humans resulted in stimulus equivalence class formation irrespectively of stimulus characteristics. However, a series of recent studies with location as the relevant stimulus dimension showed mainly negative results. This study intended to verify whether instructions clarifying the participant's tasks would improve his performance in the formation of three equivalence classes composed by the relative locations of nine squares in a three by three matrix. Ten college-student participants received minimal instructions. Eleven other students received additional instructions advising them to consider what they learned to that point (baseline) in the next trials (tests). Ten participants that received additional instructions and five that received minimal instructions formed the three equivalence classes. The additional instructions facilitated equivalence formation. However the present study also differs from previous ones in two aspects: 1) in using a different color for each class, and 2) in allowing a larger number of tests before concluding for the failure to form equivalence, and therefore allowing further opportunity for extinction of responses incompatible with the programmed contingencies.
equivalence relations; equivalence relations of location; instructions; task clarification
