Abstract:

Facial expressions are emotional signals conveyed through muscle movements, such as those in the eyes and mouth. Facial emotion recognition plays a crucial role in infant’s social and communicative development. The development of basic facial expression recognition in infants is asynchronous: the recognition of positive expressions occurs earlier than that of negative expressions, and the development of emotion perception is earlier than emotion understanding.
Infants recognize positive facial expressions earlier than negative ones. They can distinguish happy expressions when they are 2 months old, and negative expressions when they are 4-6 months old. Infant’s ability to perceive emotions develops earlier than their ability to understand emotions. The 7-month-old infant has initially possessed the emotion perception ability. They can not only distinguish the basic facial expressions, but also form a classification perception and master the visual observation strategy similar to that of adults. The development of emotional understanding is relatively lagging behind, and 12-month-old infants cannot accurately understand the emotional meaning conveyed by different the negative valence expressions. Infants' basic facial expression recognition undergoes a shift from positive bias to negative bias. In the first half of infancy, infants show an attentional bias to happy expressions, and from 5 months onwards, infants show an attentional bias to fearful expressions.
The development of infant’s ability to recognize basic facial expression recognition reflects the process from the activation of basic emotions to the formation of emotional schemas. Basic expressions are a preset system that humans evolved to adapt to the environment, and infants are born with the innate ability to express and recognize them. Once basic emotions are activated by the environment, infants acquire corresponding recognition abilites. Emotional schemas are acquired through postnatal development, and are the result of the dynamic interaction process between emotions and cognition. Both individual cognitive development and environmental stimuli play important roles in the formation of emotional schemas. The experience-expectant mechanism in the human brain enables infants to recognize positive expressions earlier than negative expressions, which helps infants to receive more feedback from adults. From the second half of infancy, infants may develop an attentional bias towards negative expression, which can aid in their better understanding of others’s feelings. There may also be a sensitive period during the second half of infancy for the development of the ability to recognize negative emotions. Moreover, the experience-dependent mechanism in the brain determines the plasticity of the brain's emotional neural network. The mother-infant relationship, family, social environment, race, and culture all can affect the development of an infant's ability to recognize facial expressions.

Key words: infant, facial expression, emotion recognition