Figure 2

Discrimination of an individual object presented in both 2D and 3D forms. It is possible that limitations of the mouse visual system may preclude mice from truly perceiving the difference between an actual 3D object and a 2D picture of that object. This experiment confirmed that the mice identify the 2D pictures and 3D objects as separate entities, as opposed to perceiving them as the same stimulus. During the sample session, naïve mice (n = 9) were placed within the Plexiglas arena insert for a maximum of 10 min where they visually explored two identical 3D objects. During the test session 24 h later, the mice were returned to the insert and allowed 5 min to visually explore the familiar 3D monkey and a 2D picture of the “familiar” monkey. The mice preferentially explored the “familiar” 2D picture over the familiar 3D object [t(8) = − 6.79, P < 0.01, d = 2.13]. This result indicates that rodents identify the 2D “familiar” picture as a stimulus visually distinct from that of the familiar 3D object. *P < 0.01 versus the familiar 3D object.