Use of an Egocentric Frame of Reference by Gouped Fish (Aphyocharax erithrurus) in a Spatial Discrmination

Abstract

Small groups of fish of a schooling species (Aphyocharax erithrurus) were trained to turn right or left in order to avoid being temporarily swept out of the water.This was achieved by a rotating avoidance paddle approaching them with one door (right or left) open. Once a learning criterion was attained, the direction of the paddle was reversed and both doors were opened. During these inversion trials, fish chose the door which was at the same side in relation to their body, showing that egocentric clues were used when facing the problem from an opposite viewpoint. When vertical black and white stripes were present at one side of the tank, a different response appeared during the inversion trials: fish passed through the door nearest to the stripes regardless of which door was open during training. It is concluded that these fish use egocentric references when the spatial problem is reversed by 180°, and that this response is overridden by a tendency to swim near a vertically striped background.