Inferring Consciousness in Phylogenetically Distant Organisms

Peter Godfrey-Smith; Inferring Consciousness in Phylogenetically Distant Organisms. J Cogn Neurosci 2024; 36 (8): 1660–1666. doi: https://doi.org/10.1162/jocn_a_02158

Abstract: The neural dynamics of subjectivity (NDS) approach to the biological explanation of consciousness is outlined and applied to the problem of inferring consciousness in animals phylogenetically distant from ourselves. The NDS approach holds that consciousness or felt experience is characteristic of systems whose nervous systems have been shaped to realize subjectivity through a combination of network interactions and large-scale dynamic patterns. Features of the vertebrate brain architecture that figure in other accounts of the biology of consciousness are viewed as inessential. Deep phylogenetic branchings in the animal kingdom occurred before the evolution of complex behavior, cognition, and sensing. These capacities arose independently in brain architectures that differ widely across arthropods, vertebrates, and cephalopods, but with conservation of large-scale dynamic patterns of a kind that have an apparent link to felt experience in humans. An evolutionary perspective also motivates a strongly gradualist view of consciousness; a simple distinction between conscious and nonconscious animals will probably be replaced with a view that admits differences of degree, perhaps on many dimensions.

Introduction

When we encounter octopuses and some other complex invertebrate animals, we find behavioral indicators, or at least suggestions, of various kinds of subjective experience. We might see suggestions of pain, for example, and can note an attentive engagement by the animal with events around them. First impressions based on behavior are not enough to infer that felt experience is actually present. If we want to work out whether it really feels like something to be one of these animals, how should we proceed? Further observation can give us a richer sense of their behavioral capacities, and we can also try to work out what is going on inside them. When we look inside, we find similarities to ourselves along with many differences. We find a nervous system, but one with a different architecture from ours. In some respects, these different nervous systems are evidently doing similar things: Octopuses and bees can see; they can navigate and learn. However, the neural structures that figure in recent attempts to explain consciousness are generally absent—they have no cortex or thalamus, for example. Which similarities between us and them matter, and which do not? How can inferences about consciousness in phylogenetically distant animals be more than speculation?

This Perspective article offers a position on these matters. The topic is consciousness or felt experience in a minimal sense—whether it feels like something to be one of these animals (Nagel, 1974). The problem will be approached through an evolutionary framing, looking at the history of nervous systems and the phylogenetic relationships between different animals alive now. I will link this evolutionary perspective to a general view about the biological basis of conscious experience, and consider several invertebrate groups. The discussion will focus on animals but will suggest conclusions about other organisms as well. My positive account of the biology of consciousness is speculative in many respects, as are its rivals. I can offer defenses for some claims, but it is not possible in a short essay to establish it as the best option. The aim of the discussion is to outline the view, link it to empirical work, and consider how it relates to some alternatives.