Delayed plasticity of an instinct: recognition and avoidance of 2 facing eyes by the jewel fish.

A model depicting 2 horizontally positioned black spots resembling facing eyes, as compared with models depicting other spot arrangements, elicits intense flight activity in young African jewel fish (Hemichromis bimaculatus) under 5 months of age and 7-month-old subadults reared apart from conspecifics with eyeless cave fish (Anoptichthys jordani). In contrast, subadults permitted to observe or interact fully with conspecifics during development exhibited attenuated discriminative flight activity. These findings suggest that visual experience with facing conspecifics, irrespective of physical contact, modifies the flight-eliciting properties of the innat mechanism subserving eye-schema recognition, but only during later maturation.