Functional equivalence in a California sea lion: Relevance to animal social and communicative interactions

Laboratory investigations into equivalence class formation suggest how animals in social and communicative contexts learn to place dissimilar individuals, signals, responses and social reinforcers into the same functional class. Kastak & Schusterman (1994, Anim. Learn. Behav, 22, 427-435) demonstrated that a California sea lion performed generalized identity matching-to-sample; that is, it chose visual stimulus A conditionally upon an identical sample A (AA matching), chose stimulus B conditionally upon sample B (BB matching) and chose stimulus C conditionally upon sample C (CC matching). The sea lion was later trained on 30 problems with similar stimuli to select comparison B conditionally upon sample A (AB matching), and trained on another 30 problems to select comparison C conditionally upon sample B (BC matching). Subsequently, the sea lion demonstrated trial-1 BA and CB matching and trial-1 AC and CA matching (Schusterman & Kastak 1993, Psychol. Rec., 43, 823-839). Matching of these derived relations defines the phenomenon of stimulus equivalence: when one member (A) of an equivalence class (ABC) becomes discriminative for a given behaviour, then B and C should become discriminative for the same behaviour. In the current study, we tested whether the sea lion could transfer the relations it had acquired between equivalence class members from a matching-to-sample paradigm to a simple discrimination paradigm. In 28 of 30 tests, the sea lion immediately transferred the discriminative function acquired by one member of an equivalence class to the remaining members of that class. Substitutability among members of an equivalence class is relevant to an analysis of referential communication, for example, the representational function of alarm calls. (C) 1998 The Association for the Study of Animal Behaviour.