Breastfeeding experience influences infant perception of emotional signals
Individuals differ in how they perceive emotional expressions, such as the tendency to perceive positive expressions as more salient than negative. This attention to emotional expressions can be reflected in the brain. The idea that these neural responses can be linked to early childhood breastfeeding experience is suggested in the results of a new study from the research group “Early Social Development” , led by Tobias Grossmann.
It is well-known that breastfeeding plays a pivotal role in the healthy growth of a child, in particular in cognitive and brain development. The extent of which breastfeeding experience might also impact social development has yet to be a major focus of scientific studies. “This is quite surprising,” says Kathleen Krol, leader of the study,”because breastfeeding is much more than just a simple meal. It is a complex, dynamic, biological as well as psychological process that is social by nature.” In a newly released study, the scientist presents data in which the duration of exclusive breastfeeding impacts infants’ neural sensitivity to happy and fearful body expressions.
According to Krol, infants who were exclusively breastfed longer had a significantly greater neural sensitivity to happy body expressions than infants with a low exclusive breastfeeding duration. The scientist speaks of a “neural bias towards happiness as a function of exclusive breastfeeding duration.”
The crucial ability to interpret the emotional expressions of others develops during the first year of life. Previous studies have extensively documented the emergence of emotion discrimination around seven months of age. “It is now important to explore what factors might contribute to individual differences in emotion perception. To gain a better understanding of this might help inform theories about how certain biases in emotional processing come about,” said Krol.
On the basis of previous research, the scientists initially hypothesized that infants with a greater experience of exclusive breastfeeding would have a higher sensitivity to positive expressions. This is due to the intricate relationship between breastfeeding and the hormone oxytocin, which is known to facilitate human prosocial behavior, and importantly, increase the salience of positive emotions.
The researchers tested eight-month-old infants in the current study. Infants were presented with fearful and happy postures while seated on their parent’s lap. (Fig.) Meanwhile, the babies wore an EEG cap, which recorded their electrical brain responses. In addition, the mothers answered a variety of questions about breastfeeding behavior and the temperament of their infants.
“The recorded EEG response indicated that infants who were exclusively breastfed longer have an increased neural sensitivity to positive body expressions than those who were exclusively breastfed for a shorter duration,” says Krol. In addition, the researchers were able to identify a linear relationship between the duration of breastfeeding and this neural sensitivity: With the increase of exclusive breastfeeding, the neural bias towards fear shifted towards one for happiness.
Kathleen Krol puts forward two possible interpretations to the findings: first, it is possible that the increased exposure to oxytocin might lead to an early “programming” effect during this sensitive stage of emotional development, such that the emotional biases witnessed here will persist later on. “Alternatively, what we are seeing may reflect a consequence of late weaning,” said Krol: “In this scenario, the later weaned infant may rely more on the mother, rendering negative or threatening information less important to attend to. Relatedly, earlier weaning (shorter exclusive breastfeeding duration) may engender processes that sensitize the infant to threatening information, as weaning is a marker for more independent functioning. ”
Regardless of the possible interpretations, the present study provides first insights into the role that breastfeeding experience plays in contributing to individual differences in the neural processing of emotions. The findings are testament to a need to better understand the impact of parental care on socio-emotional functioning in early childhood.
K. M. Krol, Purva Rajhans, Manuela Missana, and Tobias Grossmann
Duration of exclusive breastfeeding is associated with differences in infants’ brain responses to emotional body expressions
Frontiers in Behavioral Neuroscience 8, 459 (2015)