The Evolution of Consciousness in Animals

Publisher Summary The problem of an objective definition of consciousness increases several orders of magnitude when trying to recognize the physical basis of consciousness and the existence of conscious entities different from human beings. A viewpoint proposes that consciousness appeared in response to the need to develop a central control taking behavioral decisions based on motivational, sensory-spatial, and motor circumstances. To make such a decision, the organism should distinguish the sensory changes produced in the environment from those produced as a consequence of its own behavioral output. Some animals can such distinctions only using peripheral controls, while in animals with multiple spatial senses (vision, audition, olfaction, somesthesis) a central unification in form of central motor control is needed to produce a multisensory representation of the environment. A different viewpoint has been proposed, postulating that consciousness is the evolutionary result of sensation, and therefore retains the properties of sensation, that is, quality, intensity, affectivity, and duration. This review tries to develop an evolutionary tree of consciousness. It first discusses which adaptive advantage animals have acquired by consciousness. Behavior of sufficient complexity to consider the existence of consciousness could be found in three groups: arthropods, mollusks and vertebrates. The chapter analyzes the question on the adaptability of consciousness, provides a summary on the empirical proofs supporting (or rejecting) the existence of consciousness in the arthropods and mollusks is provided, examines the existence of consciousness in vertebrates.