Directional hearing in the median vertical plane by the cod

Abstract

The ability of cod (Gadus morhua) to discriminate between sound sources in the median vertical plane was studied using a cardiac conditioning technique. Masked auditory thresholds were obtained by transmitting tone and noise from separate projectors. There was a significant decrease in masking as the angular separation between tone and noise sources increased, confirming that cod is able to perform an auditory discrimination based on directional cues (Fig. 2). The power of angular resolution was studied using a directional change of a pulsed tone as the conditioning stimulus. The limit for angular discrimination was close to 16°, as compared to 20° previously reported for the horizontal plane (Fig. 4). Humans are unable to discriminate between pure tones from different directions in the median vertical plane. This difference in auditory ability between fish and humans may be attributed to the difference in habitat; the fish living in a three dimensional medium while humans are restricted to a surface.