Visual and tactile behaviors of octopus: Do they recognize their environments by cross-modal perception?

Abstract

Octopuses, a member of molluscan class, possess well-developed nervous system such as lens eyes that is anatomically similar to our own, and the relative proportion of brain to body is equivalent to vertebrates. Octopuses are also characterized with their muscular highly sensitive sensory receptors, namely, suckers on their arms. Due to these biological uniqueness, octopuses have been a target for psychological studies and were reported their advanced abilities for learning and memory, which are achieved via visual and tactile perceptions. All of these findings have come from experiments that tested single sensory perception (i.e., visual or tactile). On the other hand, it is known in vertebrates that they can integrate multiple sensory information, by which they can vividly image their environments. In this review, we will briefly introduce our knowledge for biology of octopuses with special reference to their cognition, and we will shed light on an idea for cross-modal perception in octopuses, which is based on our on-going projects for visual and tactile learning, and manipulation of arms in tropical octopuses inhabiting the coastal waters of the Ryukyu Archipelago.