This research investigated the source of an ostensible reflexivity effect in pigeons reported by Sweeney and Urcuioli (2010). In Experiment 1, pigeons learned two symmetrically reinforced symbolic successive matching tasks (hue-form and form-hue) using red-green and triangle-horizontal line stimuli. They differed in their third concurrently trained baseline task: form-form matching with stimuli appearing in the symbolic tasks (triangle and horizontal) for one group versus hue-hue matching with stimuli not appearing in the symbolic tasks (blue and white) for the other. During subsequent non-reinforced probe tests, all pigeons in the former group and most pigeons in the latter group responded more to the comparisons on matching than on non-matching red-green probes. In Experiment 2, the latter group was tested on non-reinforced form-form probes. One of the four pigeons responded significantly more to the comparisons on matching than on non-matching triangle-horizontal probes. These data are consistent with generalized identity and at least one other interpretation of the reflexivity results and question the functional stimulus assumption of Urcuioli’s (2008) stimulus-class theory.


This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.


reflexivity, generalized identity, successive matching, stimulus equivalence, stimulus classes, pigeons, key peck

Date of this Version




Included in

Psychology Commons