A replication and extension of the antisymmetry effect in pigeons.

Pigeons trained on successive AB symbolic matching show emergent BA antisymmetry if they are also trained on successive AA oddity and BB identity (Urcuioli, 2008, Experiment 4). In other words, when tested on BA probe trials following training, they respond more to the comparisons on the reverse of the nonreinforced AB baseline trials than on the reverse of the reinforced AB baseline trials (the opposite of an associative symmetry pattern). The present experiment replicated this finding. In addition, it showed that antisymmetry also emerged after baseline training on successive AB symbolic matching, AA identity, and BB oddity, consistent with the prediction from Urcuioli's (2008) theory of pigeons' stimulus-class formation. Together, these results provide further empirical support for that theory including the proposition that the functional stimuli in pigeons' successive matching consist of the nominal stimuli plus their ordinal positions within a trial.