Jonathan Birch

We consider the relationship between neural and behavioural evidence for animal consciousness. We critically examine two recent studies: one neural and one behavioural. The first, on crows, finds different neural activity depending on whether a stimulus is reported as seen or unseen. However, to implicate this neural activity in consciousness, we must assume that a specific conditioned behaviour is a report of conscious experience. The second study, on macaques, records behaviours strikingly similar to patterns of conscious and unconscious perception in humans. However, confounds are only ruled out in human subjects, presupposing substantial neural similarity between humans and macaques. Taken together, the two studies reveal a sense in which neural and behavioural research rely on each other. Looking ahead, these two types of evidence could prove to be either mutually reinforcing or mutually undermining. The science of animal consciousness needs both neural and behavioural evidence, ideally obtained as part of a single coordinated programme.

Consciousness has an important role in ethics: when a being consciously experiences the frustration or satisfaction of its interests, those interests deserve higher moral priority than those of a behaviourally similar but non-conscious being. I consider the relationship between this ethical role and an a posteriori (or ‘type-B’) materialist solution to the mind-body problem. It is hard to avoid the conclusion that, if type-B materialism is correct, then the reference of the concept Phenomenal Consciousness is radically indeterminate between a neuronal-level property that is distinctive to mammals and a high-level functional property that is much more widely shared. This would leave many non-mammalian animals (such as birds, fish, insects and octopuses) with indeterminate moral status. There are ways to manage this radical moral indeterminacy, but all of these ways lead to profoundly troubling consequences.

I reflect on the commentaries on my 'skill hypothesis' from Andrews/Westra, Tomasello, Sterelny, and Railton. I discuss the difference between normative cognition and the broader category of action-guiding representation, and I reflect on the relationship between joint intentionality and normative cognition. I then consider Sterelny and Railton's variants on the skill hypothesis, which highlight some important areas where future evidence could help us refine the account: The relative importance of on-The-fly skill execution vs. longer-Term strategizing, the relative importance of toolmaking vs. collaborative foraging, and the question of whether norms are encoded in control models themselves or in the goals and ideals that our control models help us pursue.

What makes fast, cumulative cultural evolution work? Where did it come from? Why is it the sole preserve of humans? We set out a self-assembly hypothesis: cultural evolution evolved culturally. We present an evolutionary account that shows this hypothesis to be coherent, plausible, and worthy of further investigation. It has the following steps: (0) in common with other animals, early hominins had significant capacity for social learning; (1) knowledge and skills learned by offspring from their parents began to spread because bearers had more offspring, a process we call CS1 (or Cultural Selection 1); (2) CS1 shaped attentional learning biases; (3) these attentional biases were augmented by explicit learning biases (judgements about what should be copied from whom). Explicit learning biases enabled (4) the high-fidelity, exclusive copying required for fast cultural accumulation of knowledge and skills by a process we call CS2 (or Cultural Selection 2) and (5) the emergence of cognitive processes such as imitation, mindreading and metacognition-'cognitive gadgets' specialized for cultural learning. This self-assembly hypothesis is consistent with archaeological evidence that the stone tools used by early hominins were not dependent on fast, cumulative cultural evolution, and suggests new priorities for research on 'animal culture'. This article is part of the theme issue 'Foundations of cultural evolution'.

Over the past two decades, Ginsburg and Jablonka have developed a novel approach to studying the evolutionary origins of consciousness: the Unlimited Associative Learning (UAL) framework. The central idea is that there is a distinctive type of learning that can serve as a transition marker for the evolutionary transition from non-conscious to conscious life. The goal of this paper is to stimulate discussion of the framework by providing a primer on its key claims (Part I) and a clear statement of its main empirical predictions (Part II).

There is increasing recognition that the welfare needs of cephalopod molluscs and decapod crustaceans are important. Current commercial practices involving these animals include a range of potential threats to their welfare, such as conditions of farming, capture, transport, and slaughter. This article draws from and updates our 2021 review for the UK Government, recommending a range of relatively simple and impactful changes that could benefit welfare while highlighting important research gaps that should be prioritised to facilitate the drafting of guidelines for best-practice.

There is no agreement on whether any invertebrates are conscious and no agreement on a methodology that could settle the issue. How can the debate move forward? I distinguish three broad types of approach: theory-heavy, theory-neutral and theory-light. Theory-heavy and theory-neutral approaches face serious problems, motivating a middle path: the theory-light approach. At the core of the theory-light approach is a minimal commitment about the relation between phenomenal consciousness and cognition that is compatible with many specific theories of consciousness: the hypothesis that phenomenally conscious perception of a stimulus facilitates, relative to unconscious perception, a cluster of cognitive abilities in relation to that stimulus. This “facilitation hypothesis” can productively guide inquiry into invertebrate consciousness. What is needed? At this stage, not more theory, and not more undirected data gathering. What is needed is a systematic search for consciousness-linked cognitive abilities, their relationships to each other, and their sensitivity to masking.

Skyrms, building on the work of Dretske, has recently developed a novel information-theoretic account of propositional content in simple signalling systems. Information-theoretic accounts of content traditionally struggle to accommodate the possibility of misrepresentation, and I show that Skyrms’s account is no exception. I proceed to argue, however, that a modified version of Skyrms’s account can overcome this problem. On my proposed account, the propositional content of a signal is determined not by the information that it actually carries, but by the information that it would carry at the nearest separating equilibrium of the underlying evolutionary dynamics. I show that this amended account yields reasonable ascriptions of false propositional content in a well-known formal model of the evolution of communication (the ‘Philip Sidney’ game), and close with a discussion of the serious but perhaps not insuperable difficulties we face in applying the account to examples of signalling in the real world.

The theories of inclusive fitness and multilevel selection provide alternative perspectives on social evolution. The question of whether these perspectives are of equal generality remains a divisive issue. In an analysis based on the Price equation, Queller argued (by means of a principle he called the separation condition) that the two approaches are subject to the same limitations, arising from their fundamentally quantitative-genetical character. Recently, van Veelen et al. have challenged Queller’s results, using this as the basis for a broader critique of the Price equation, the separation condition, and the very notion of inclusive fitness. Here we show that the van Veelen et al. model, when analyzed in the way Queller intended, confirms rather than refutes his original conclusions. We thereby confirm (i) that Queller’s separation condition remains a legitimate theoretical principle and (ii) that the standard inclusive fitness and multilevel approaches are indeed subject to the same limitations.

Rapid progress in artificial intelligence (AI) capabilities has drawn fresh attention to the prospect of consciousness in AI. There is an urgent need for rigorous methods to assess AI systems for consciousness, but significant uncertainty about relevant issues in consciousness science. We present a method for assessing AI systems for consciousness that involves exploring what follows from existing or future neuroscientific theories of consciousness. Indicators derived from such theories can be used to inform credences about whether particular AI systems are conscious. This method allows us to make meaningful progress because some influential theories of consciousness, notably including computational functionalist theories, have implications for AI that can be investigated empirically.

Motivational trade-off behaviours, where an organism behaves as if flexibly weighing up an opportunity for reward against a risk of injury, are often regarded as evidence that the organism has valenced experiences like pain. This type of evidence has been influential in shifting opinion regarding crabs and insects. Critics note that (i) the precise links between trade-offs and consciousness are not fully known; (ii) simple trade-offs are evinced by the nematode worm Caenorhabditis elegans, mediated by a mechanism plausibly too simple to support conscious experience; (iii) pain can sometimes interfere with rather than support making trade-offs rationally. However, rather than undermining trade-off evidence in general, such cases show that the nature of the trade-off, and its underlying neural substrate, matter. We investigate precisely how.

Can octopuses feel pain and pleasure? What about crabs, shrimps, insects, or spiders? How do we tell whether a person unresponsive after severe brain injury might be suffering? When does a fetus in the womb start to have conscious experiences? Could there even be rudimentary feelings in miniature models of the human brain, grown from human stem cells? And what about AI? These are questions about the edge of sentience, and they are subject to enormous, disorienting uncertainty. The stakes are immense, and neglecting the risks can have terrible costs. We need to err on the side of caution, yet it's often far from clear what 'erring on the side of caution' should mean in practice. When are we going too far? When are we not doing enough? The Edge of Sentience presents a comprehensive precautionary framework designed to help us reach ethically sound, evidence-based decisions despite our uncertainty.

Could emotions be a uniquely human phenomenon? One prominent theory in emotion science, Lisa Feldman Barrett’s Theory of Constructed Emotion (TCE), suggests they might be. The source of the sceptical challenge is that TCE links emotions to abstract concepts tracking socio-normative expectations, and other animals are unlikely to have such concepts. Barrett’s own response to the sceptical challenge is to relativize emotion to the perspective of an interpreter, but this is unpromising. A more promising response may be to amend the theory, dropping the commitment to the abstract nature of emotion concepts and allowing that, like olfactory concepts, they have disjunctive sensory groundings. Even if other animals were emotionless, this would not imply they lack morally significant interests. Unconceptualized valenced experiences are a sufficient basis for morally significant interests, and such experiences may occur even in the absence of discrete, constructed emotions.

Some patients, following brain injury, do not outwardly respond to spoken commands, yet show patterns of brain activity that indicate responsiveness. This is 'cognitive-motor dissociation' (CMD). Recent research has used machine learning to diagnose CMD from electroencephalogram recordings. These techniques have high false discovery rates, raising a serious problem of inductive risk. It is no solution to communicate the false discovery rates directly to the patient's family, because this information may confuse, alarm and mislead. Instead, we need a procedure for generating case-specific probabilistic assessments that can be communicated clearly. This article constructs a possible procedure with three key elements: (1) A shift from categorical 'responding or not' assessments to degrees of evidence; (2) The use of patient-centred priors to convert degrees of evidence to probabilistic assessments; and (3) The use of standardised probability yardsticks to convey those assessments as clearly as possible.

‘Sentience’ sometimes refers to the capacity for any type of subjective experience, and sometimes to the capacity to have subjective experiences with a positive or negative valence, such as pain or pleasure. We review recent controversies regarding sentience in fish and invertebrates and consider the deep methodological challenge posed by these cases. We then present two ways of responding to the challenge. In a policy-making context, precautionary thinking can help us treat animals appropriately despite continuing uncertainty about their sentience. In a scientific context, we can draw inspiration from the science of human consciousness to disentangle conscious and unconscious perception (especially vision) in animals. Developing better ways to disentangle conscious and unconscious affect is a key priority for future research.

When two agents engage in a joint action, such as rowing together, they exercise joint know-how. But what is the relationship between the joint know-how of the two agents and the know-how each agent possesses individually? I construct an “active mutual enablement” (AME) account of this relationship, according to which joint know-how arises when each agent knows how to predict, monitor, and make failure-averting adjustments in response to the behaviour of the other agent, while actively enabling the other to make such adjustments. I defend the AME account from three objections, and I then use this account as the platform for an examination of the reducibility (or otherwise) of joint know-how to joint propositional knowledge. A summative account of joint propositional knowledge is incompatible with the reduction of joint know-how to joint propositional knowledge, whereas a distributive account is not (although serious difficulties for any such reduction remain). I close by highlighting some open questions the AME account brings into view concerning the evolutionary origin and scaling up of joint know-how.

Hamilton introduced two conceptions of social fitness, which he called neighbour-modulated fitness and inclusive fitness. Although he regarded them as formally equivalent, a re-analysis of his own argument for their equivalence brings out two important assumptions on which it rests: weak additivity and actor's control. When weak additivity breaks down, neitherfi tness concept is appropriate in its original form. When actor's control breaks down, neighbour-modulated fitness may be appropriate, but inclusive fitness is not. Yet I argue that, despite its more limited domain of application, inclusive fitness provides a distinctively valuable perspective on social evolution.

Martha Nussbaum’s Justice for Animals calls upon humanity to secure for all sentient beings the central capabilities they need to flourish. This essay review critically examines the ethical and scientific foundations of Nussbaum’s position. On the ethical side, we explore the tension between a robust defence of animal rights and political liberalism, which requires tolerance of a range of reasonable views. On the scientific side, we reflect on how our uncertainty regarding the distribution of sentience in the natural world leaves us uncertain about how many claimants of justice there are and about the relative strength of their claims. We bring out some further problems with Nussbaum’s views on animal killing and pest control. We also reflect on how animal welfare science might be done differently if guided by Nussbaum’s framework.

Peter Carruthers has recently argued for a surprising conditional: if a global workspace theory of phenomenal consciousness is both correct and fully reductive, then there are no substantive facts to discover about phenomenal consciousness in non-human animals. I present two problems for this conditional. First, it rests on an odd double-standard about the ordinary concept of phenomenal consciousness: its intuitive non-gradability is taken to be unchallengeable by future scientific developments, whereas its intuitive determinacy is predicted to fall by the wayside. Second, it relies on dismissing, prematurely, the live empirical possibility that phenomenal consciousness may be linked to a core global broadcast mechanism that is (determinately) shared by a wide range of animals. Future developments in the science of consciousness may lead us to reconsider the non-gradability of phenomenal consciousness, but they are unlikely to lead us to accept that there are no facts to discover outside the paradigm case of a healthy adult human.

We introduce the virtual special issue on content in signalling systems. The issue explores the uses and limits of ideas from evolutionary game theory and information theory for explaining the content of biological signals. We explain the basic idea of the Lewis-Skyrms sender-receiver framework, and we highlight three key themes of the issue: (i) the challenge of accounting for deception, misinformation and false content, (ii) the relevance of partial or total common interest to the evolution of meaningful signals, and (iii) how the sender-receiver framework relates to teleosemantics.

Altruistic deception (or the telling of “white lies”) is common in humans. Does it also exist in non-human animals? On some definitions of deception, altruistic deception is impossible by definition, whereas others make it too easy by counting useful-but-ambiguous information as deceptive. I argue for a definition that makes altruistic deception possible in principle without trivializing it. On my proposal, deception requires the strategic exploitation of a receiver by a sender, where “exploitation” implies that the sender elicits a behaviour in the receiver that is beneficial in a different type of situation and is expressed only because the signal raises the probability, from the receiver's standpoint, of that type of situation. I then offer an example of a real signal that is deceptive in this sense, and yet potentially altruistic (and certainly cooperative): the purr call of the pied babbler. Fledglings associate purr calls with food, and adults exploit this learned association, in the absence of food, to lead fledglings away from predators following an alarm call. I conclude by considering why altruistic deception is apparently so rare in non-human animals.

Animal welfare scientists face an acute version of the problem of inductive risk, since they must choose whether or not to affirm attributions of mental states to animals in advisory contexts, knowing that their decisions hold significant consequences for animal welfare. In such contexts, the burden of proof should be sensitive to the moral consequences of error, but a framework for setting appropriate burdens of proof is lacking. Through reflection on two cases—the case of pain, and the case of cognitive enrichment—I arrive at a tentative general framework based on the principle of expected welfare maximization. I then discuss the limitations of this framework and the important questions it leaves open.