Most animals use multiple sensory modalities to obtain information about objects in their environment. There is a clear adaptive advantage to being able to recognise objects cross- modally and spontaneously (without prior training with the sense being tested) as this increases the flexibility of a multisensory system, allowing an animal to perceive its world more accurately and to react more quickly to environmental changes. So far, cross-modalobject recognition is known only from a few mammalian species1-5, raising the question whether such a high-level function may be associated with complex mammalian brain structures and may be absent in animals lacking a cerebral cortex. Here we use an object discrimination paradigm based on operant conditioning to show, for the first time, that a non- mammalian vertebrate, the weakly electric fish Gnathonemus petersii, is capable of performing spontaneous cross-modal object recognition, and that the sensory inputs are weighted dynamically during object discrimination. We found that fish trained to discriminate two objects with either vision or the active electric sense, were subsequently able to accomplish the task using only the untrained sense. Furthermore, the performance of the electrically trained fish in the visual transfer tests increased with deceasing reliability of the electric sense at longer distances, showing that at short distances sensory transfer is masked by the dominance of the electric sense. Our results show that a brain structure like the mammalian neocortex is not necessary for cross-modal object recognition and suggest that this ability may be a phylogenetically ancient mechanism of vertebrates.
展开▼
