Investigating harbor seal's (Phoca vitulina) visual cognition: Which features they predominately use to discriminate 2D objects, brightness and shape?

Abstract

Characteristics of visual functions differ between species as they have evolved independently to adapt to their habitat. Animals use shape and brightness to visually discriminate between objects. In this study, we used five harbor seals (Phoca vitulina) to determine how amphibious animals use these two features of visual function. The subjects were trained in a two-alternative forced-choice task to discriminate between a dark gray circle (correct object) and a light gray triangle. In the test phase, we prepared two novel objects in addition to the two objects used in the training. We randomly presented two of the four objects to the seals and compared the selection rate of each object. The results revealed that harbor seals discriminate between objects based on shape rather than brightness. The visual cognitive pattern of seals may be a result of adaptation to a light-scarce underwater environment. This is the first study to provide preliminary evidence of the visual cognitive features of seals.