ilative/accommodative interplay, infancy may be an especially important time inasmuch as structural changes in the nervous system are occurring. These central nervous system changes will be occurring during a period of maximal exposure to highly articulated facial expressions. There, is peak exposure to fully articulated positive emotions during early infancy. Except for abused infants, exposure to examples of negative affect probably occurs somewhat later in infancy. During toddlerhood (also known as the "terrible twos," with good reason), the child's activities will bring him or her into direct collision with parental proscriptions; there will probably be ample opportunity to observe fullblown examples of parental anger, and, during toilet training, other expressions. As the child leaves the home at school age he or she will find the occurrences of such salient affective displays sharply curtailed. Infancy then, and to a certain extent early childhood, will be a time for important learning about affect, learning that is relatively uncontaminated by socio-cultural display mores. To return to the theme that introduced this chapter, it is perhaps not a coincidence that the expressions displayed by mothers to their infants have very much the same "exaggerated" or full-blown quality seen in the expressions used in emotion recognition studies -- the same kinds of studies that have been successful in establishing the universality of human emotion expressions. In light of the literature reviewed in this chapter it also should come as no surprise that there are individual differences in the ability to perceive and produce various emotion expressions. In the opening years of life it is the mother, and possibly also the father, who provides both a link with the universals as well as an introduction to individuality.
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