At birth, the infant has only the most elementary emotional life. Newborns show an expression of disgust, for example, in response to strong tastes, and show surprise in reaction to sudden changes. They also show interest, which developmental psychologists consider an emotion in its own right. 

    By ten months, infants display the full range of what are considered the basic emotions: joy, anger, sadness, disgust, surprise, and fear. The emergence of the basic emotions during the first year or two of life seems to be 

programmed by a biological clock for brain development.  As the appropriate brain maturation occurs, the various emotions appear in an infant’s repertory. For example, studies of brain activity in ten-month-olds show that the right frontal regions are more active during positive emotions, and the left during negative emotions.