A series of studies with human fetuses at different gestational ages showed that they prefer to orient their heads and eye lenses toward face-like configurations of lights projected through the uterine wall rather than toward inverted light configurations. Fetuses also exhibited stronger lens movements in response to continuous lights rather than flashing ones. The research was published in Developmental Science.
Human faces are among the most important and salient stimuli for children, playing a crucial role in early social and cognitive development. Newborns show a preference for face-like patterns from birth, demonstrating an innate tendency to focus on human faces. This preference helps infants develop attachment bonds with caregivers, which are essential for emotional and psychological well-being.
Faces provide key social cues, such as emotions and intentions, which children learn to interpret over time. Infants and young children also use facial expressions to regulate their own emotions, looking at caregivers for reassurance in unfamiliar situations. Atypical responses to faces, such as reduced eye contact, are sometimes early indicators of neurodevelopmental conditions like autism spectrum disorder.
Study author Irene Ronga and her colleagues sought to explore whether the preference for human faces observed in newborns is already present in fetuses. They also aimed to determine when this preference begins to develop. To investigate this, they conducted three experiments in which they projected specific light configurations through the uterine wall and used ultrasound to monitor changes in the fetuses’ eye lens and head orientations.
The study participants were 60 healthy pregnant women with normal pregnancies, enrolled at Sant’Anna University Hospital, Città della Salute e della Scienza (Turin, Italy). All participating women had normal body mass indexes at the beginning of their pregnancies. This corresponded to 60 fetuses included in the study: 20 at 37 weeks of gestation, 20 at 31 weeks, and 20 at 26 weeks.
In the experiments, the researchers shone lights in the form of three red dots through the participating women’s uterine walls so that they could be detected by the fetuses’ eyes. These lights were either arranged in a face-like configuration—two lights next to each other with one below them (roughly corresponding to the positions of two eyes and a mouth on a face)—or an inverted configuration, with two lights next to each other and one above them.
In one experiment, the lights were continuous. In another, the researchers projected them as either continuous or flashing lights. They also tested the reactions of fetuses at different gestational ages to these stimuli.
The first experiment showed that fetuses tended to move their eye lenses toward the face-like configuration of lights more often than toward the inverted configuration. The second experiment revealed that fetuses exhibited stronger responses to continuous lights than to flashing ones. When analyzing responses at different fetal ages, the researchers found that reactions to the lights were strongest in fetuses at 37 weeks of gestation, followed by those at 31 and 26 weeks.
The study contributes to the scientific knowledge on how fetuses processes visual stimuli. However, it should be noted that the study was conducted on a relatively small groups of fetuses. Further studies on larger samples are needed to confirm the findings.
The paper, “At First Sight: Fetal Eye Movements Reveal a Preference for Face-Like Configurations From 26 Weeks of Gestation,” was authored by Irene Ronga, Karol Poles, Carlotta Pace, Marta Fantoni, Josephine Luppino, Pietro Gaglioti, Tullia Todros, and Francesca Garbarini.
