E motional development and temperamental individuality have been topics
of compelling interest to students of infancy because they help shape the
child's encounters with the social and object world. Emotional reactions
organize how a baby responds to events, and parents devote careful attention
to these reactions in their efforts to manage, pacify, accentuate, or redirect them.
Over the course of the first 2 years of life, changes in a child's emotional reac-
tions demarcate important transitions in development that are meaningful to
caregivers, whether they concern the first elicited smiles, the earliest indications
of stranger wariness, or the emergence of nascent expressions of embarrassment.
These emotional reactions are significant also because they are viewed by parents
as indicators of an emerging individuality—as cues to what the child's behav-
ioral style is like now and will be like in future years. Along with variations
in activity level and other dimensions, individual differences in predominant
mood, soothability, and emotional intensity define dimensions of temperamental

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