Perceptual Awareness in Human Infants: What is the Evidence?

Abstract

Perceptual awareness in infants during the first year of life is understudied, despite the philosophical, scientific, and clinical importance of understanding how and when consciousness emerges during human brain development. Although parents are undoubtedly convinced that their infant is conscious, the lack of adequate experimental paradigms to address this question in preverbal infants has been a hindrance to research on this topic. However, recent behavioral and brain imaging studies have shown that infants are engaged in complex learning from an early age and that their brains are more structured than traditionally thought. I will present a rapid overview of these results, which might provide indirect evidence of early perceptual awareness and then describe how a more systematic approach to this question could stand within the framework of global workspace theory, which identifies specific signatures of conscious perception in adults. Relying on these brain signatures as a benchmark for conscious perception, we can deduce that it exists in the second half of the first year, whereas the evidence before the age of 5 months is less solid, mainly because of the paucity of studies. The question of conscious perception before term remains open, with the possibility of short periods of conscious perception, which would facilitate early learning. Advances in brain imaging and growing interest in this subject should enable us to gain a better understanding of this important issue in the years to come.

Full text

Perceptual Awareness in Human Infants:
What is the Evidence?
Ghislaine Dehaene-Lambertz
Abstract
■Perceptual awareness in infants during the first year of life
is understudied, despite the philosophical, scientific, and clin-
ical importance of understanding how and when conscious-
ness emerges during human brain development. Although
parents are undoubtedly convinced that their infant is con-
scious, the lack of adequate experimental paradigms to
address this question in preverbal infants has been a hin-
drance to research on this topic. However, recent behavioral
and brain imaging studies have shown that infants are engaged
in complex learning from an early age and that their brains are
more structured than traditionally thought. I will present a
rapid overview of these results, which might provide indirect
evidence of early perceptual awareness and then describe how
a more systematic approach to this question could stand
within the framework of global workspace theory, which iden-
tifies specific signatures of conscious perception in adults.
Relying on these brain signatures as a benchmark for con-
scious perception, we can deduce that it exists in the second
half of the first year, whereas the evidence before the age of
5 months is less solid, mainly because of the paucity of studies.
The question of conscious perception before term remains
open, with the possibility of short periods of conscious per-
ception, which would facilitate early learning. Advances in
brain imaging and growing interest in this subject should
enable us to gain a better understanding of this important
issueintheyearstocome. ■
INTRODUCTION
The extended periods of sleep, limited vocalizations, and
lack of clear voluntary actions in the weeks following birth
have long been interpreted as indicators of a poor and
empty mental life in infants, or a “blooming, buzzing con-
fusion”(James, 1890). These interpretations reflect an
enduring implicit bias to downplay infants’abilities until
there is overwhelming evidence to back them up. In addi-
tion, researchers often tend to challenge the parents’
belief that their infant is already competent, contrasting
the emotional perspective of parents with objective scien-
tific observation. These prejudices explain why certain
questions, such as consciousness, have received little
attention. However, since the 1980s, research into cogni-
tive development has gradually proved parents right,
revealing an astonishingly competent infant capable of
rapid and complex learning and consciousness is begin-
ning to be seen as a possible research question in infants.
Before delving into the limited number of studies that
directly address this question, and for readers less familiar
with developmental issues, we offer a succinct overview of
the cognitive and learning capacities of human infants and
their cerebral basis. This lays the foundations for a more
systematic approach to the study of consciousness from
the earliest age.
EVIDENCE OF EARLY LEARNING IN
HUMAN INFANTS
At birth, neonates are able to recognize their mother’s
voice (DeCasper & Fifer, 1980), their native language
(Mehler et al., 1988), and a plausible biological movement
(Simion, Regolin, & Bulf, 2008). They imitate adult facial
and manual movements (Meltzoff & Moore, 1977), dis-
criminate numbers (Izard, Sann, Spelke, & Streri, 2009)
and geometrical shapes (Turati, Simion, & Zanon, 2003),
and so forth. When placed on a crawler that compensates
for their motor immaturity, they may even move toward a
speaker playing their native language (Hym et al., 2023).
In addition to their remarkable ability to learn familiar
features of the environment, as demonstrated by their
preference for the mother’s voice and language, newborns
exhibit an impressive capacity to learn even within the lim-
itations of a time-limited experimental setting. For
instance, full-term neonates are able to segment a speech
stream based on the transition probabilities between sylla-
bles (Fló, Benjamin, Palu, & Dehaene-Lambertz, 2022;
Fló et al., 2019). They also detect an unusual repetition
within an alternation pattern (Panzani, Mahmoudzadeh,
Wallois, & Dehaene-Lambertz, 2023), or a second-order
regularity pattern (Moser et al., 2020, 2021). During the
following months, infants continue to build on their suc-
cess, and long before the end of the first year of life, they
have developed social skills (Hamlin, Wynn, & Bloom,
2007), can interpret actions in relation to an actor’s goals
(Southgate,Begus,Lloyd-Fox,diGangi,&Hamilton,
Université Paris-Saclay
© 2024 Massachusetts Institute of Technology Journal of Cognitive Neuroscience 36:8, pp. 1599–1609
https://doi.org/10.1162/jocn_a_02149