Functional specializations of the right and left side of the brain have been shown to occur in all vertebrate classes and are known to affect various aspects of behaviour. Recent evidence suggests that cerebral lateralization influences cooperative predator inspection in fish. In order to confirm these findings, predator inspection was studied in female guppies (Poecilia reticulata) while a shoalmate (their own mirror image) was visible either on their left or right side. We used laboratory-reared guppies with no natural experience of predators. One half of the subjects were sensitized to a predator by repeatedly introducing a hungry individual of the species Lepomis gibbosus into their home tank prior to the test, while the other half remained without any experience of predators. Guppies with prior experience of the predator showed a greater tendency to approach a live predator when their shoalmate was visible on their right side.