When a baby first gains consciousness is a complex challenge in developmental neuroscience and psychology. Since infants cannot verbally report experiences, scientists rely on objective measurements of brain activity and behavior to determine when subjective awareness begins. Research focuses on observable biological and psychological markers that indicate a transition from reflex to experience. Consciousness is not a single switch that turns on, but rather a gradual process of developing awareness.
Defining Consciousness in Developmental Science
Developmental scientists distinguish between different forms of awareness. The most basic form is sentience, the capacity to feel, perceive, and have subjective experiences, often called “qualia.” This foundational awareness is distinct from higher-order consciousness, which involves complex cognitive functions like self-awareness and introspection.
Consciousness is viewed as a gradient where the complexity of awareness increases over time. Researchers measure this gradient using theoretical frameworks, such as the Integrated Information Theory (IIT). IIT proposes that consciousness arises from a system’s capacity to integrate information, and the level of consciousness can be quantified mathematically.
Another influential framework is the Global Neuronal Workspace Theory (GNWT), which posits that conscious experience occurs when information is globally broadcast across widely distributed neural networks. While IIT emphasizes posterior brain regions, GNWT highlights the role of communication involving the prefrontal cortex. These theories help identify the functional architecture necessary for a baby to have a unified, subjective experience.
Measuring Awareness in the Developing Brain
Since infants are non-verbal, researchers rely on sensitive neuroimaging and behavioral techniques. Electroencephalography (EEG) and functional Magnetic Resonance Imaging (fMRI) track functional connectivity and brain activity patterns linked to conscious states. Scientists look for patterns in the infant brain that resemble neural markers of conscious perception observed in adults.
One such marker is a delayed slow wave in the brain’s electrical activity, similar to the P300 component seen in adult EEG data, which is associated with conscious visual perception. This P300-like wave has been documented in infants as young as five months old, suggesting they possess conscious visual impressions.
Researchers have also applied Integrated Information Theory principles to EEG data from preterm infants. They found that the measure of integrated information increases with age and can differentiate between states like being awake, REM sleep, and non-REM sleep.
Behavioral methods provide complementary evidence, such as the preferential looking paradigm, which relies on the infant’s tendency to look longer at novel stimuli. In habituation, an infant’s looking time at a repeated stimulus decreases. Subsequent recovery of interest (dishabituation) upon seeing a new stimulus indicates they have perceived and remembered the initial item. This demonstrates that the infant brain actively processes and discriminates sensory information, a foundational requirement for awareness.
Tracking the Emergence of Consciousness
Consciousness is not a single moment, but a progression beginning before birth. The neural correlate of consciousness is thought to emerge around 24 weeks of gestation, marking the third trimester. This timing corresponds to the establishment of thalamocortical connections, the neural pathways that relay sensory information from the periphery to the cerebral cortex.
Before this stage, sensory nerves have not fully connected to the cortex, but once connected, the fetus may begin to process external stimuli, such as the mother’s voice. Although the fetus is mostly in a sleep-like state, signs suggest consciousness begins to form during this late prenatal period. The transition at birth, characterized by intense sensory stimulation and the start of breathing, triggers an arousal that awakens the newborn.
The newborn is considered conscious, albeit at a low level, with the initial formation of the default mode network (DMN) occurring soon after birth. Postnatally, the complexity of a baby’s conscious experience rapidly increases. By five months, the presence of the adult-like P300 brain wave suggests infants are capable of conscious visual impressions, and markers like intentional behavior and explicit memory suggest increasingly complex awareness developing throughout the first year.
Markers of Self-Awareness in Infancy
The later development of consciousness shifts from basic external awareness to higher-order awareness of oneself as a distinct entity. This capacity for self-recognition is a major milestone tracked using behavioral experiments. The most common method is the mirror test, or rouge test, which assesses an infant’s self-recognition.
In the test, an experimenter places a mark on the infant’s nose or forehead before placing the infant in front of a mirror. Infants under a year old typically treat the reflection as another child. Self-awareness is confirmed when the child touches the mark on their own face, rather than trying to touch the image in the mirror.
Most children achieve explicit mirror self-recognition around 18 to 24 months of age. This ability marks a significant leap in understanding their body schema and identity as a separate individual. While consciousness emerges much earlier, this later milestone demonstrates the maturation of complex human awareness.