Project Summary
Much of infants’ learning occurs through social interactions with others, and the quality of these early
social interactions is consequential for linguistic and cognitive development. In particular, there is substantial
variation in input quality across the spectrum of socioeconomic status (SES), often putting infants from lower-
SES families at risk for learning challenges1-4. However, current investigations into how input impacts learning
have had a dominant focus on infants’ language input, undercutting understanding of the full complexity of
infants’ everyday communicative environments. Further, minimal research has studied the neural mechanisms
through which input quality influences learning. The proposed research will address both of these limitations,
exploring relations between input quality and neural activity during natural caregiver-infant interactions.
Specific Aim 1 is to determine how caregivers across the SES spectrum use a suite of interconnected
signals when communicating with their 18-month-old infants. While substantial evidence links variability in
SES, language input quality, and language outcomes, we propose to broaden the current understanding of
input quality by examining five dimensions of communication: language, action, gesture, emotion, and touch.
Together, we refer to these signals as “infant-directed communication” (IDC). Specific Aim 2 examines how the
quality of IDC influences brain-to-brain coupling during natural, dynamic interactions between caregivers and
infants. To do so, we will use dual-brain functional near-infrared spectroscopy (fNIRS), a methodology that was
recently developed in the Princeton Baby Lab. Finally, Specific Aim 3 asks how IDC and neural coupling at 18
months independently and jointly relate to infants’ focused attention, a standardized measure of cognitive
skills, and vocabulary growth, thereby providing links to established measures of cognitive and linguistic
development. These aims provide the first investigation of neural coupling as a mechanism by which SES-
related variability in the quality of infants’ environment influences later learning. In this way, the proposed
research both advances current theories of social learning and enhances our ability to inform interventions in a
meaningful and ecologically valid way.
Through these aims, the applicant will acquire training in dual-brain neuroscience methods, broaden her
theoretical knowledge of language development and communication, acquire advanced statistical training, and
work with diverse populations including lower-SES families. Her sponsor, Dr. Casey Lew-Williams, has
extensive experience in all of these areas and is known for his outstanding mentorship. The co-sponsor, Dr. Uri
Hasson, has pioneered the study of brain-to-brain coupling. The training environment at Princeton University
provides all resources needed for conducting the proposed research, as well as broad opportunities for
intellectual and professional development. Together, this training will prepare the applicant well for a career as
a tenure-track professor at a research university.
