Nonhuman species have been shown to be able to use information about the hierarchical structure of serial patterns involving the consequences of their behavior. In the present article, three lines of research are examined that provide evidence for such learning. The first shows that rats are sensitive, not only to the trial by trial sequence of the changing magnitude of reward but also to the monotonic decrease in those rewards. The second line of research shows that in an eight-lever box, rats can divide a complex sequence of required responses into chunks (right, right, left; right, right, left; etc.), defining a "rule." The third line of research demonstrates that when pigeons are trained on a sequence in which there is a monotonically increasing or decreasing response requirement for each reward, the sequences themselves take on additional incentive value leading to suboptimal choice to leave the schedule. Monotonically increasing response requirements take on a relatively negative reward value, whereas monotonically decreasing response requirements take on positive reward value. The three lines of research demonstrate that animals are sensitive not only to the immediate consequences of their behavior but also to the pattern of future consequences.
The New York Declaration on Animal Consciousness (NYD) shows that nonhuman animal awareness is an active research area. However, several unresolved challenges identified by Griffin in the 1976 scientific study of animal consciousness continue to deter researchers. We sidestep debate around studies of consciousness and instead explore how studies identified in the NYD address Tinbergen's Four Questions. We found that ontogeny is overlooked in studies of animal consciousness, whereas most studies focus on mechanism. Although our efforts do not resolve long-standing challenges in consciousness research, we do provide a different perspective that may hold prescriptive utility for future research.
In 1976, Donald R. Griffin asked us to consider the question of animal consciousness. Specifically, do animals have mental experiences akin to ours? This question was actually asked more than a century earlier, and the attempts to answer it prompted generations of researchers to adopt a more objective analysis of behavior and cognition. I briefly review the history of this controversy and explain how- by focusing on behavior-significant scientific progress has been accomplished without engaging in mentalistic theorizing.
The observed difference in relative brain size between endotherms and ectotherms raises questions about potential resulting disparities in brain function between these two groups. Until recently, no clear cognitive advantage was found in endotherms, with ectotherms occasionally even outperforming them in seemingly complex tasks. However, recent research on working memory-a core executive function-in a teleost fish species suggests that cognitive differences may lie in more fundamental processes. Here, we develop two working hypotheses that arose from this finding. First, the apparent absence of working memory in a fish, and possibly other ectotherms, may stem from their inability to voluntarily control their attentional focus. Instead, the environment would drive, through other cognitive processes, changes in that focus. In 2011, in the dichotomic vision of Kahneman consisting of automatic System 1 and voluntary System 2, fish could rely only on System 1. We call this the Lack of Attentional Control hypothesis. Second, to explain why smaller-brained species may nevertheless outperform larger-brained species in some cognitive tasks, we propose the Cognition-Opportunities-Needs framework, which posits that cognitive abilities and learning opportunities provide non-mutually exclusive mechanisms for meeting ecological demands. Although these hypotheses require extensive empirical validation, they represent a first step toward a comprehensive theoretical perspective on cognitive diversity and evolution across species and major vertebrate clades.
Donald R. Griffin's scientific contributions and his influential role in advancing animal cognition research are described, particularly his controversial proposal that many animals may be conscious. Griffin's views, the tenets of his new field of Cognitive Ethology, challenged established scientific thinking and had far-reaching effects in biology, psychology, philosophy, and animal welfare. Griffin also created the field of echolocation and conducted landmark studies of avian navigation. His efforts revealed complex animal abilities.
This commentary focuses primarily on my interactions with Don, particularly during my sabbatical at Rockefeller University when his campaign for cognitive ethology was gaining momentum. I recount my research on reptile behavior and cognition, my collaboration with Don and others at RU, and my role in advancing his ideas while contextualizing them within 19th-century comparative psychology. I also discuss some later developments in cognitive ethology, including critical anthropomorphism, the challenges of integrating subjective experience into behavioral science, and Griffin's lasting influence on animal cognition research.
Broad declarations of consciousness in nonhuman animals seed needless confusion in our field, grossly overstate our meager evidence, are not needed to advocate for animal welfare, and provide ammunition to anti-science advocates.
Research on animal consciousness has historically focused on mammals and birds, leaving reptiles and amphibians largely overlooked. These taxa, however, display evidence of cognitive flexibility, goal-directed behavior, associative learning, and affective capacities despite lacking a neocortex. Studying them offers insight into the minimal neural and cognitive requirements for conscious experience and challenges the assumption that consciousness depends on mammal-like brain structures. Recognizing the potential awareness of reptiles and amphibians also carries important ethical and conservation implications, given their widespread use in research, captivity, and ongoing population declines. Broadening the study of consciousness to include these groups can illuminate the evolutionary distribution of subjective experience and foster a more inclusive understanding of animal awareness.
Awareness can be thought of as the ability to imagine. I describe three lines of animal research thought to be associated with human awareness. In opaque imitation an observer is presumed to imagine that its own unseen behavior matches that of a demonstrator. In episodic memory, one can metaphorically travel back in time to imagine a past event. In acquired equivalence, two stimuli, A and B, are both associated with a common stimulus, C. Learning something new about one stimulus, A, transfers to the other stimulus, B. These and other examples suggest that some form of awareness may occur in animals.
Animal sentience research has historically emphasized negative emotions such as pain, fear, and distress, reflecting urgent ethical concerns. Yet positive emotions-including joy, curiosity, and satisfaction-are crucial for survival, fitness, and adaptive behavior. Recognizing and promoting these states represents the next frontier in sentience science, offering a more complete understanding of emotional capacities across species. This commentary discusses conceptual and evolutionary considerations, highlights methodological challenges in studying positive experiences, and outlines practical implications for welfare in research and agricultural contexts. By integrating positive and negative states, we can ensure that animals not only avoid harm but also experience enriched, meaningful lives.
The New York Declaration on Animal Consciousness suggests the evidence for nonhuman animal awareness is overwhelming, but it fails to support how any necessarily weighs on the topic of consciousness. I suggest here that the Declaration is ill-considered from the outset. Observations of others' behavior cannot be satisfactory evidence of the kind of consciousness we seek. We should instead consider the conditions under which an organism may come to observe itself. Such self-observation is dependent on discriminative contingencies maintained by a verbal community. As such, only verbal organisms (e.g., most human beings) should be called "conscious."
Whether invertebrates possess the capacity for subjective experiences, particularly that of pain, is a frontier question in cognitive ethology. Central to this inquiry is the examination of pain-like behaviours elicited by noxious stimulation under leading sentience frameworks. Here we discuss our concerns on how the usage of the terms 'noxious' and 'aversive' in an interchangeable manner throughout past and emerging work may hamper current assessments of invertebrate pain-related literature. We briefly discuss the etymology of these terms, provide use cases that illustrate how conflation obscures interpretation, and propose a simple yet effective solution.
The study of animal consciousness has long struggled between analogy-based interpretations of behavior and reductionist accounts that explain complex actions as nonconscious. Building on Donald Griffin's proposal to use animal behaviors as suggestive indications rather than direct evidence, I argue that progress lies in refining these markers by drawing on insights from both neurobiology and the study of simple life forms. Neurocognitive research on humans identifies recurring features of consciousness that can better inform the selection of functionally relevant candidate cognitive markers in animals. Work on simpler organisms suggests that even basic life forms integrate internal states when guiding self-initiated behavior, suggesting an evolutionary basis underpinning consciousness. Taken together, these perspectives suggest that behavioral markers should not only identify the presence of Integrating these approaches hopefully allows cognitive ethology to move beyond polarized debates and develop more robust behavioral markers of consciousness across species.
A recent declaration that consciousness is widespread throughout the animal kingdom might suggest that finding evidence of consciousness is the proper basis on which to decide an animal's welfare matters. The welfare of spiders, the animals we use for our research on cognition, matters to us but we have no evidence of spider consciousness or see how there ever could be. Asking for evidence of consciousness is asking for a subjective, first-person understanding of what a spider experiences. To us, reference to consciousness is an unappealingly people-centered perspective from which to appreciate spiders.
We distinguish between ethical and scientific approaches to nonhuman consciousness. Ethically, we endorse liberal inference of consciousness to mitigate moral hazard. Scientifically, we advocate for skepticism because no convincing testable causal role for consciousness in behavior has been articulated. Claims that complex behaviors necessitate consciousness lack clear mechanistic justifications, and many complex behaviors appear to proceed without consciousness. Progress in the study of consciousness will require specifying what consciousness causes that cannot occur without it.
Although humans consider themselves and other humans who are awake, functioning, and responsive to be conscious, the question of nonhuman consciousness is still open for debate. Research groups have suggested various criteria for determining how to assess consciousness in nonhumans, but a definitive answer still eludes the scientific community. Here, I provide some comments with respect to the study of avian consciousness in general and Grey parrots (Psittacus erithacus) in particular.
Animal cognition research has accumulated strong behavioural and neurobiological evidence for memory of specific events in non-human animals. However, the definition of episodic memory remains tethered to subjective criteria. I motivate a revised, measurement-aligned definition that centres objectively testable episode representations (what-where-when) and treats the conscious experience of recollection as a separable component (ecphory). This reframing accommodates evidence from food-cache paradigms, hippocampal replay/preplay, vicarious trial-and-error, and targeted memory reactivation. Phenomenology remains relevant as convergent evidence for episodic recollection in humans, but is not required for cross-species claims. I outline a practical route to consensus terminology.
It is parsimonious to assume that animals solve issues of internal representation and cognitive flexibility in similar ways to us. We think that multiple mechanisms that different animals use to accomplish similar outcomes is an important issue to consider when thinking about awareness and consciousness. As such, the nature of awareness and consciousness may differ across species. To illustrate these points, we discuss differences across species in episodic memory, blindsight, and visual illusions and what these differences mean for understanding consciousness in nonhuman animals.
