The present experiment investigated whether pigeons can show associative symmetry on a two-alternative matching-to-sample procedure. The procedure consisted of a within-subject sequence of training and testing with reinforcement, and it provided (a) exemplars of symmetrical responding, and (b) all prerequisite discriminations among test samples and comparisons. After pigeons had learned two arbitrary-matching tasks (A-B and C-D), they were given a reinforced symmetry test for half of the baseline relations (B1-A1 and D1-C1). To control for the effects of reinforcement during testing, two novel, nonsymmetrical responses were concurrently reinforced using the other baseline stimuli (D2-A2 and B2-C2). Pigeons matched at chance on both types of relations, thus indicating no evidence for symmetry. These symmetrical and nonsymmetrical relations were then directly trained in order to provide exemplars of symmetry and all prerequisite discriminations for a second test. The symmetrical test relations were now B2-A2 and D2-C2 and the nonsymmetrical relations were D1-A1 and B1-C1. On this test, 1 pigeon showed clear evidence of symmetry, 2 pigeons showed weak evidence, and 1 pigeon showed no evidence. The previous training of all prerequisite discriminations among stimuli, and the within-subject control for testing with reinforcement seem to have set favorable conditions for the emergence of symmetry in nonhumans. However, the variability across subjects shows that methodological variables still remain to be controlled.

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The notion of superstitious behavior can provide a basic background for understanding such notions as illusions and beliefs. The present study investigated the social mechanism of the transmission of superstitious behavior in an experiment that utilized participant replacement. The sample was composed of a total of 38 participants. Participants performed a task on a computer: they could click a colored rectangle using the mouse. When the rectangle was in a particular color, the participants received points independently of their behavior (variable time schedule). When the color of the rectangle was changed, no points were presented (extinction). Under an Individual Exposure condition, ten participants worked alone on the task. Other participants were exposed to the same experimental task under a Social Exposure condition, in which each participant first learned by observation and then worked on the task in a participant replacement (chain) procedure. The first participant in each chain in the Social Exposure condition was a confederate who worked on the task "superstitiously," clicking the rectangle when points were presented. Superstitious responding was transmitted because of the behavior of the confederate. This also influenced estimates of personal control. These findings suggest that social learning can facilitate the acquisition and maintenance of superstitious behavior and the illusion of control. Our data also suggest that superstitious behavior and the illusion of control may involve similar learning principles.

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Article history: Received: 15-04-2016 Revised: 29-06-2016 Accepted: 12-08-2016 Key words: conditional discrimination; equivalence class formation; symmetry; Sapajus sppThe present study presents a procedure to assess the property of symmetry by comparing the acquisition of conditional relations that are consistent and inconsistent with this property in a capuchin monkey (Sapajus spp.). One young male monkey underwent arbitrary matching-to-sample training. The experiment had four phases: Phase 1.1 (establishing A1B1 and A2B2 relations), Phase 1.2 (reinforcing B1A1 and B2A2 relations, consistent with the property of symmetry), Phase 2.1 (establishing A3B3 and A4B4 relations), and Phase 2.2 (reinforcing B3A4 and B4A3 relations, inconsistent with the property of symmetry). A comparison between Phase 1.2 (consistent) and Phase 2.2 (inconsistent) showed faster acquisition of consistent relations (B1A1 and B2A2) than inconsistent relations (B3A4 and B4A3). The results suggest that the established conditional discriminations may have the property of symmetry and confirm the potential of comparative analysis between the acquisition of conditional discriminations as a promising procedure to evaluate equivalence class formation in nonhuman subjects.