April 16, 2026
Although each of us was once a baby, infant consciousness remains mysterious and there is no received view about when, and in what form, consciousness first emerges. Some theorists defend a ‘late-onset’ view, suggesting that consciousness requires cognitive capacities which are unlikely to be in place before the child’s first birthday at the very earliest. Other theorists de- fend an ‘early-onset’ account, suggesting that consciousness is likely to be in place at birth (or shortly after) and may even arise during the third trimester. Progress in this field has been difficult, not just because of the challenges associated with procuring the relevant behavioral and neural data, but also because of uncertainty about how best to study consciousness in the absence of the capacity for verbal report or intentional behavior. This review examines both the empirical and methodological progress in this field, arguing that recent research points in favor of early-onset accounts of the emergence of consciousness.
The onset of experience
Nearly everyone who has held a newborn infant has wondered what, if anything, it is like to be a baby. What kinds of conscious states are characteristic of infant experience? In what ways is infant experience continuous with ordinary adult (or childhood) experience, and in what ways is it unique? Indeed, do newborn infants have any kind of experience at all, or does consciousness emerge only weeks, perhaps months, after birth? Few would doubt that consciousness is generally in place by the age of 1 year, where children have a wide range of perceptual and cognitive capacities and produce a rich suite of communicative behaviors. At the same time, none of the neural machinery required for consciousness is in place immediately after conception (e.g., neurogenesis does not even begin until weeks later [1]). At one developmental time point, the human organism lacks the capacity for consciousness; at another time point, it has acquired that capacity. When does this change take place?
Although speculation on the emergence of experience dates back to the earliest reflections on the human mind, it is only in the past few decades that such speculation has been informed by detailed understanding of brain development. There is, however, no consensus as to when consciousness first emerges and the range of candidate answers offered here is extremely wide. At one end of the spectrum are accounts that suggest that consciousness might be in place from as early as 24 to 26 weeks gestational age (see Glossary), which is when thalamocortical connectivity is first established [2,3]. At the other end of the spectrum are accounts according to which consciousness is unlikely to be in place significantly prior to the child’s first birthday [4]. In between, of course, lie a wide range of possible accounts, including the view that consciousness arises soon after birth [5], perhaps even during the process of birth itself.
1Monash University, Melbourne, VIC, Australia
2Brain, Mind, and Consciousness Pro- gram, Canadian Institute for Advanced Research, Toronto, Canada
3Institute for Neuro-modulation and Neuro-technology, University Hospital and University of Tübingen, Tübingen, Germany
4Institute for Advanced Consciousness Studies, Santa Monica, CA, USA 5Thomas Mitchell Professor of Cognitive Neuroscience, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
6Masonic Institute for the Developing Brain, University of Minnesota, Minneapolis, MN, USA
7Trinity College Institute of Neuroscience
and Global Brain Health Institute, Trinity College, Dublin, Ireland
8These authors contributed equally (co- first authorship) to this work.
*Correspondence: timothy.bayne@monash.edu (T. Bayne).
Trends in Cognitive Sciences, December 2023, Vol. 27, No. 12 https://doi.org/10.1016/j.tics.2023.08.018 1135
© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
Understanding when (and in what form) consciousness first emerges should be high on the agenda of consciousness science. Not only would it have important implications for debates about the mechanisms underlying consciousness [6], it would also have important clinical, ethical, and perhaps even legal implications (Box 1). Drawing on advances that have been made in detecting consciousness in other challenging contexts, including in patients with severe brain dam- age [7], this paper examines what we know about the first of glimmerings of human awareness. Although it would be premature to make definitive claims about when consciousness first emerges, we suggest that current evidence indicates that consciousness is likely to be in place by early infancy, and may even begin before birth. Our primary aim, however, is not to provide a definitive answer to the question of when (and in what form) consciousness first emerges, but to present recent developments within a compelling framework that will advance discussion of this important issue.
Methodological challenges
The notion of consciousness with which we are concerned in this article involves the possession of an experiential point of view. An organism is conscious if (and only if) it has a subjective perspective – if there’s ‘something that it’s like’ to be that organism [8]. Different kinds of conscious states (or ‘contents’) are distinguished from each other in terms of what it’s like to be in them. What it’s like to see a face is distinct from what it’s like to hear a melody and each of those experiences is itself distinct from what it’s like to feel pain. Note that here we treat ‘consciousness’ as a synonym for ‘awareness’. Our focus here is on the development of ‘core’ [9] or ‘primary’ [10] consciousness and not on the development of forms of consciousness that require reflection, self-consciousness, or off-line cognition [11,12]. These features can be absent even in adult states of consciousness [13,14] and are unlikely to be present in the earliest stages of experience.
Because consciousness is a subjective phenomenon, attempts to identify its presence in infancy confront serious methodological challenges. Clearly, the standard tools for studying consciousness in adults and older children, such as the capacity to produce verbal reports or follow
commands, are unavailable and we are forced to rely on less direct markers (or indicators) of consciousness. A theorist’s choice of markers is crucially important here, and much of the debate surrounding the emergence of consciousness stems from more fundamental disagreement about the kinds of states and capacities that function as markers of consciousness.
Late-onset views versus early-onset views
Some theorists take consciousness to require capacities which are almost certainly not available to young infants. According to Perner and Dienes [4], consciousness requires the capacity to rep- resent mental states as such and is thus (they conclude) unlikely to be in place before the age of 1 year. Frith [15] equates the contents of consciousness with ‘shareable knowledge’, suggesting that consciousness involves representations that are ‘coded independently of egocentric coordinates’. Although Frith draws no inferences about when consciousness is likely to first emerge, his position would also seem to suggest that consciousness is unlikely to be acquired prior to the child’s first birthday. Perhaps the most radical of the ‘late-onset’ proposals is due to Carruthers [16], who argues that consciousness does not emerge until the age of 3 years on the grounds that this is when children first acquire the concepts that he takes to be required for consciousness, such as ‘appears’ and ‘seems’.
At the same time, many potential markers of consciousness can be found in early infancy. Full- term neonates exhibit visual pursuit and fixation [17] and they produce a rich suite of reactions in response to noxious stimuli, including increased heart-rate and skin conductance, limb- withdrawal, grimacing, and brain activity distinctive to noxious stimuli [18]. Indeed, neonates can distinguish their mother’s voice from that of a stranger’s [19,20] and can discriminate dynamic facial expressions of happiness from disgust [21]. This capacity for basic environmental responsiveness distinguishes young infants from brain-injured patients in the unresponsive wakefulness syndrome (UWS) (‘vegetative state’), who do not respond appropriately to their surroundings and who do not strike us as subjects of awareness. The question, of course, is whether behavioral indicators of consciousness in young infants are to be trusted. A related question is whether there are reasons to think that consciousness might emerge even before these behavioral indicators do.
The theory-first approach
Clearly, methodological questions are of crucial importance here. Without guidance as to which cognitive, behavioral, or neural responses we ought to employ as markers of consciousness, the debate over when consciousness first emerges threatens to become a stand-off between those who favor cognitively demanding measures of consciousness (and thus orient towards ‘late-onset’ views) and those who favor relatively undemanding measures (and thus orient towards ‘early-onset’ views).
In response to this dilemma, one might be tempted to begin with a theory of consciousness, and ask what that theory implies with respect to infant consciousness. Although it is certainly useful to consider what particular theories might imply with respect to the emergence of consciousness, the theory-first approach faces serious challenges. For one, there is little agreement as to which theories of consciousness are most likely to be correct (or even plausible). A recent review
[6] identified more than 20 neuro-biological accounts, many of which have importantly different variants. This failure of theoretical convergence would not be problematic if the field were moving towards consensus, but that does not appear to be the case [22,23]. Worse, rival theories, including those that are some of the most influential, suggest very different accounts of when (and in what form) consciousness first emerges (Box 2).
