April 19, 2026
experience. From birth, infants show behavioral sensitivity to their mother’s voice [19] and the prosody of their native language [82,83], although research into neural responses to speech (as opposed to comparable auditory stimuli) has produced mixed results. Selective responses to music in nonprimary auditory cortex have been reported in 1-month-olds [84] and sensitivity to violations of musical beat has been reported in newborns [85]. An ERP study of preterm infants (Box 4) sug- gests that by 30 weeks gestational age, the Perisylvian region is able to support the detection of both phonetic (/da/ versus /ga/) and voice (male versus female) change [86] and there is even ev- idence that the fetus recognizes its mother’s voice [87].
A particularly challenging question concerns the development of the infant’s awareness of its own body and its capacities for action. Although some work has been done in this area [88–91], bodily and agentive experience in the infant has received significantly less attention than perceptual ex- perience. It is plausible that bodily experiences reach conscious awareness earlier than other as- pects of sensory experience, possibly even before birth. Consider the loose analogy of a sensory isolation float tank, which is sometimes compared with the womb (e.g., [92]). Adults who float in isolation tanks experience enhanced interoception despite (or perhaps because of) minimization of all external sensory afferents [93]. On this basis, it might be suggested that interoceptive expe- rience emerges before exteroceptive experience.
For the most part, the development of consciousness is a story of perceptual expansion, in which the infant becomes perceptually sensitive to a wider range of environmental features as it ages. However, perceptual narrowing, in which infants lose the capacity to discriminate between fea- tures that they had previously been sensitive to, also occurs. For example, 6- to 10-month-olds raised in English-speaking households are able to discriminates between consonants used in Hindi (but not English) that monolingual English-speaking adults cannot discriminate [94] (for a re- view see [95]), but that ability is lost by 10 months of age. Perceptual narrowing also occurs in vowel discrimination, in which 4-month-olds have the capacity to discriminate between non-native vowel sounds (that is, vowel sounds that do not feature in the language to which they have been exposed), which they lose by 10 months of age [96], and in lexical tone discrimination, in which young infants (who have not been exposed to tonal languages) have the capacity to dis- criminate between lexically significant tones, which they too lose by 10 months of age [97]. Per- ceptual narrowing is not restricted to speech comprehension, but also occurs in the domain of face perception. For example, 3-month-old infants are as good at discriminating between other-race faces as they are at discriminating between same-race faces, but by 9 months of age they have lost that capacity (whilst showing improvements in same-race discriminability) [98].
The character of perceptual experience is determined not just by the features that are encoded but also by its spatial and temporal structure. Here, there is evidence that the structure of infant consciousness differs in fundamental ways from that of adult consciousness [99]. Using a crowding-based paradigm, Farzin et al. [100] showed that the effective spatial resolution of visual perception increases from 6 months to 15 months, but that even at 15 months of age it is only half that of adults. Objects that can be recognized when they are presented by themselves in the pe- riphery are not recognized when presented with flankers (i.e., ‘crowded’) until they are only 3° from fixation, implying that infants may have limited awareness of individual parts in a crowded scene as compared with adults.
An even more striking contrast between infant and adult experience concerns the temporal struc- ture of visual awareness. This can be probed using the attentional blink, a phenomenon in which the second of two visual targets goes undetected due to the subject’s attention being captured by the first target. A recent study found that the attentional blink was 6 six times longer in 5- month-old infants than it is in adults, and that although its duration shortened as infants aged (by 8 months of age it had halved), it does not reach adult levels of length until the age of 3 years [101]. Further evidence that the capacity of consciousness is significantly restricted in infants comes from the finding that 3–12 month-old infants parse animated movies into fewer events (i.e., events of longer duration) than adults do [102] and, correspondingly, integrate sensory information over longer temporal windows [103].
Taken as a whole, these findings suggest that the infant’s stream of consciousness is character- ized by a reduction of perceptual content at any one point in time, but that the range of perceptual features to which young infants are experientially sensitive may be wider, in certain domains, at least, than that to which older infants are experientially sensitive.
Concluding remarks
Although the problem of identifying when and in what form consciousness begins is very far from being solved, the developments reviewed here suggest that the study of infant consciousness is now a legitimate field within the science of consciousness. Just as recent methodological ad- vances are beginning to provide tentative (albeit limited) answers to questions about conscious- ness in non-human animals [24] and severely brain-injured individuals [104], they are also beginning to provide tentative (albeit limited) answers to questions about the first stirrings of human experience. In particular, some newer strands of evidence seem to point towards con- sciousness having an early onset, rather than a late onset (as has often been assumed). Although ‘early’ in this context potentially encompasses the prenatal period, we emphasize that this evi- dence is still from late (third trimester) pregnancy, generally after 35 weeks of gestation [65].
Of course, there is much we do not know (see Outstanding questions). A better understanding of infant consciousness will require improved techniques for collecting data about the developing brain. In particular, new innovations in MEG, such as optically pumped magnetometers, may
