Scientists have outlined three evolutionary stages of consciousness, from basic alarm responses to self-awareness, suggesting it is an ancient trait shared widely across species. New research highlights that birds exhibit forms of sensory perception and self-consciousness similar to mammals, challenging previous assumptions about its origins. This framework, known as the ALARM theory, emphasizes survival and social functions.
Consciousness, the subjective experience that colors daily life from pleasant sensations to painful ones, evolved to enhance survival and social coordination, according to philosophers Albert Newen and Carlos Montemayor. They propose three forms in their ALARM theory: basic arousal, general alertness, and reflexive self-consciousness.
Basic arousal emerged first in evolutionary history as a rapid response to threats. Newen explains, "Evolutionarily, basic arousal developed first, with the base function of putting the body in a state of ALARM in life-threatening situations so that the organism can stay alive." Pain serves as a key signal here, prompting actions like fleeing or freezing to protect the body from damage.
General alertness followed, enabling organisms to prioritize critical stimuli amid distractions. For instance, attention might shift from a conversation to the smell of smoke, allowing learning of causal links, such as smoke indicating fire. Montemayor notes, "This makes it possible to learn about new correlations: first the simple, causal correlation that smoke comes from fire and shows where a fire is located. But targeted alertness also lets us identify complex, scientific correlations."
Reflexive self-consciousness, which involves reflecting on one's own states, thoughts, and actions, developed alongside these basics. It supports memory, future planning, and social integration. A hallmark is mirror self-recognition, seen in human children around 18 months and in animals like chimpanzees, dolphins, and magpies. Newen states, "Reflexive consciousness, in its simple forms, developed parallel to the two basic forms of consciousness. In such cases conscious experience focuses not on perceiving the environment, but rather on the conscious registration of aspects of oneself."
Recent studies by Gianmarco Maldarelli and Onur Güntürkün extend this to birds, showing they possess sensory consciousness beyond mere reactions. Pigeons interpret ambiguous images subjectively, alternating views like humans, while crow brain signals align with perceived rather than external stimuli. Bird brains feature the nidopallium caudolaterale (NCL), analogous to the mammalian prefrontal cortex, with dense connections for flexible processing. Güntürkün observes, "The avian equivalent to the prefrontal cortex, the NCL, is immensely connected and allows the brain to integrate and flexibly process information." Their forebrain connectome mirrors mammalian patterns, satisfying criteria from theories like the Global Neuronal Workspace.
Birds also display basic self-perception. Pigeons and chickens distinguish mirror images from real conspecifics, responding contextually—a sign of situational self-consciousness, per Güntürkün: "Experiments indicate that pigeons and chickens differentiate between their reflection in a mirror and a real fellow member of their species, and react to these according to context. This is a sign of situational, basic self-consciousness."
These findings, published in Philosophical Transactions of the Royal Society B in 2025, indicate consciousness arose early in evolution, functioning effectively across diverse brain structures without a cerebral cortex.
