Transitive inference (TI) is a form of logical reasoning that involves using known relationships to infer unknown relationships (A . B; B . C; then A . C). TI has been found in a wide range of vertebrates but not in insects.Here, we test whether Polistes dominula and Polistes metricus paper wasps can solve a TI problem. Wasps were trained to discriminate between five elements in series (A 0 B2, B 0 C2, C 0 D2, D 0 E2), then tested on novel, untrained pairs (B versus D). Consistent with TI, wasps chose B more frequently than D. Wasps organized the trained stimuli into an implicit hierarchy and used TI to choose between untrained pairs. Species that form social hierarchies like Polistes may be predisposed to spontaneously organize information along a common underlying dimension. This work contributes to a growing body of evidence that the miniature nervous system of insects does not limit sophisticated behaviours.

Although developmental plasticity facilitates the evolutionary origin of many traits, the role of plasticity in the origin of novel communication systems has received little attention. If plasticity mediates the origin of new communication systems, exposure to a novel environment will induce new traits that could function as signals or receiver responses. Here, we test whether plasticity facilitates the origin of individual recognition. We reared a species of paper wasp that naturally lacks individual recognition (Polistes metricus) with a relative that has facial patterns that signal individual identity (Polistes fuscatus). We found P. metricus reared with individual identity signals learned unique wasp faces significantly more accurately than P. metricus reared without individual identity signals. However, exposure to individual identity signals was not sufficient to induce individual recognition in social contexts. These results suggest that if variable facial patterns arose in P. metricus, wasps would immediately improve their ability learn variable facial patterns, thereby facilitating the origin of individual face recognition. Improved learning is an initial step toward individual recognition that would need to be refined by selection to produce an established signaling system. Developmental plasticity may be an underappreciated factor facilitating the evolutionary origin of novel recognition systems.

Setting: A large university hospita1 with gynecologic outpatient operations performed irl un integrated operating room suite. Patients:Sixty adult women (ASA physical status I or II) undergoing an outpatient