Are Humans, Animals, Cells, and Plants All Conscious?

New York Declaration on Animal Consciousness ”, signed in April by more than 300 researchers, proposed that a possibility of consciousness exists in most animals.

In June, still in New York, took place the first presentation of the results of the opposing collaboration Cogitatewhich organizes a collaboration between teams that oppose two theories of consciousness. The goal being that they define the experiences to be carried out between them to prove one or the other of the conceptions they defend.

This confrontation brings together neuroscience experts and philosophers seeking a consensus between: the theory of global workspace (GNWT), carried by Stanislas Dehaene, and the theory of integrated information (IIT), proposed by Giulio Tononi. The GNWT proposes that the interaction between several regions and specific processes of the brain be necessary for consciousness, which emerges following first automatic processing only if the information is amplified by different networks of specialized neural. The IIT proposes that consciousness emerges from a system that generates and confronts information. In this proposition the possibility of consciousness is not reduced to the brain.

The review Neuronone of the most influential scientific journals in the community of neuroscience, proposed in May 2024 a special issue on consciousness. The articles show that if the neurobiological substrates of consciousness have aroused many research efforts in recent decades, the fact remains that neuroscientists do not agree. They analyze five different theories of consciousness. Despite the absence of a common definition of the term “consciousness”, used both as an “experience”, including sensitive perceptions of the outside world (color vision), and as a subjective experience, which is constructed a posteriori by integrating different sources of information, the group develops convergences between these competing and apparently contradictory theories.

Biological bases of consciousness always unknown

Without going into details and arguments concerning these different, the work shows that there is no unified theory of consciousness and that we still do not know the biological bases of consciousness. The old questions around dualism, which distinguish physical world and psychic world and monism supporting the uniqueness of the two worlds still do not seem ready to be decided.

However, even without a unified theory, the possibility of conscious experience is no longer the prerogative of humans. It diffuses through the phylogenetic tree, being now recognized in many groups of animals, including insects. The common denominator between all these approaches seems to be the presence of a brain, characteristic shared by the majority of animals, even if it is small and of simple structure. Sponges devoid of brain and nervous systems are not included in the family of conscious beings. But what about bivalves (oysters or mussels for example) which are only provided with ganglia bringing together their neurons, will they soon join the family of conscious beings?

But could consciousness exist outside this famous nervous system? This radical idea was notably proposed a few years ago by FRANISK BALUSKA, a cellular biologist, professor at the University of Bonn, and Arthur Reber, psychologist, professor at British Columbia University.

A consciousness in each living being?

They proposed that conscience would have emerged very early during evolution among unicellular organizations, and would even be coincident with the appearance of life. Consciousness would therefore be an intrinsic property of life. This proposal is based on the observation that all cells, whether isolated or integrated into a multicellular organism, have an impressive ability to perceive their environment, to process information allowing them to make basic decisions in response to external stimuli. Certain unicellular organizations can for example release molecules to signal to each other.

These processes could be considered as a form of primitive consciousness. And if this proposal ignores the presence of a nervous system, it is however based in particular on the electrical excitability of the cells. The neuron and the brain are considered to be hyperoptimized systems in one of the parts of the living, allowing human consciousness.

This theory remains of course very controversial, in particular due to the lack of shared definition of consciousness. Many scientists consider that this “cellular consciousness” would simply be a metaphor to describe complex biochemical and biophysical processes, without it being necessary to include a notion of consciousness. They criticize this theory, using a traditionally definition of consciousness involving a neurobiological system and a subjective, unlikely experience? In any case difficult to demonstrate at the cellular level.

Conscious plants?

Continuing their reflections, FRANISK BALUSKA and other colleagues proposed the IIT theory developed by Giulio Tononi as a possible framework to explore the question of a form of “proto-consciousness” among plants.

Applying Iit to plants involves examining how plants perceive, integrate and respond to information in their environment without having a central nervous system. Plants could act consciously depending on the Iit. They receive and incorporate signals from various sources and respond to it in a coordinated manner thanks to an internal communication network made up of cellular connections, vascular beams connecting all parts of the plant, in particular by electrical signals. They consider that these highly interconnected characteristics and communication networks could correspond to the IIT information integration requirement allowing plants a unified response despite the absence of a centralized nervous system. Although the authors consider that it is only a minimum level of consciousness, this data was of course immediately challenged.

The main opposite arguments are that the theories of consciousness are based on the existence of neurons and the impossibility of proving that plants have a subjective experience of their environment. Iit also authorizing consciousness in various non -living systems, it would not be sufficient to prove the consciousness of plants. Even if this hypothesis remains speculative and certainly requires more research to better understand the relationship between biological complexity and consciousness, the idea that plants can be studied using IIT theory could make it possible to explore other forms of information processing in biological systems, whether or not have brains. On the other hand, it is not certain that these approaches help the proponents of Iit, the latter having been recently controversial, and described as “non-testable pseudoscience” in a letter written by 124 neuroscientific.

To our knowledge no attempt to demonstrate another theory of consciousness has been attempted on brainless organisms. On the other hand, following the work of Claude Bernard who indicated, in 1878, “what is alive must feel and can be anesthetized, the rest is dead”, different teams whose ours, were interested in the effects of anesthetics, one of the important tools of the study of the neurobiology of consciousness, on brain -free organisms.

The theory of cellular consciousness, as well as the exploration of the theory of Iit in organisms without neurons can appear provocative, they however offer a fascinating perspective and open new ways to understand the foundations of consciousness and the emergence of behaviors in the living reign. Just as the progressive attribution of an awareness to groups of animals increasingly distant from humans in the phylogenetic tree, which relaunch and extend a thorny philosophical and scientific question.

These reflections obviously also open up many ethical questions concerning non -human organisms and, of course, machines connected to artificial intelligence, which could be part of a continuum of consciousness. Many tools and protocols are still to be developed to test what remains of the hypotheses and, why not, consider an adversarial collaboration on brainless consciousness.