Heading in the rat: Determination by environmental shape

After a 75-sec intratrial delay, rats that had been shown the location of hidden food within a rectangular box correctly dug at that location in a second identical box, which had been moved into the same position within the room. For some rats, the opposing ends of the boxes were differentiated by distinctive corner panels; for others, there were no panels. When, during the delay interval, the turntable supporting both boxes was rotated by more than 180°, so that the second box no longer took the place of the first box within the room, the rats showed performance decrements. Nevertheless, 4 subjects selected the correct location significantly more often than the rotationally equivalent location, which corresponds to the correct location when the ends of the box are confused. The amount of rotation had no significant effect for any rat. In a final phase, the rats were denied perceptual access to cues outside the test box, which now had differentiating corner panels for all rats. Despite the distinctive panels, no rat showed a significant difference between correct digs and rotational errors; that is, no rat reliably distinguished one end of the box from the other. Results confirm previous findings that rats rely primarily on environmental shape to establish their heading. They ignore distinctive features of the surfaces that define environmental shape, even when the shape by itself is insufficient to establish a unique orientation.