Stimulus control topographies and tests of symmetry in pigeons

Karen Marie Lionello-DeNolf, Purdue University

Abstract

When animals are tested for symmetry (the ability to match B to A after being trained to match A to B), they often match at chance. Some researchers attribute the absence of symmetry in animals to an inherent inability to form that emergent relation. However, it is also possible that matching-to-sample (the procedure most often used to assess symmetry) introduces variables that preclude symmetry—e.g., the changing of the locations of the stimuli in testing relative to training, and the lack of sample discrimination training of the sort required for symmetry. Previous research has shown that when stimuli change locations, animals treat them as if they are different stimuli (Lionello & Urcuioli, 1998). In the present study, pigeons were tested for the emergence of symmetry after being trained on A-B matching under conditions designed to avoid these problems. In Experiment 1, training was conducted with samples that appeared in two locations in order to minimize the impact of stimulus location on pigeons' matching (Lionello-DeNolf & Urcuioli, 2000). Despite this, pigeons still showed no evidence for symmetry although A-B matching transferred to novel locations. Experiments 2a and 2b included training on additional MITS tasks in order to explicitly train all the discriminations required for accurate performance on symmetry. Despite this, pigeons matched at chance. Experiment 3 examined the impact of directly training symmetrical matching relations with some stimulus sets on its subsequent emergence with different stimulus sets. Like the results of the other experiments, the pigeons matched at chance. Experiment 2a tested for another emergent relation, reflexivity, and Experiment 3 tested for a third emergent relation, transitivity. On both of these tests, pigeons matched at chance. The results of these experiments increase the plausibility of the argument that symmetry and other emergent relations indicative of equivalence class formation may be beyond the capabilities of the pigeon.

Degree

Ph.D.

Advisors

Urcuioli, Purdue University.

Subject Area

Psychology|Experiments|Behaviorial sciences

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