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This article addresses the issue of general versus specific measures of infant intelligence in the second year of life and suggests a strategy for assessing specific abilities. The second year is particularly interesting because of its many significant transitions in cognitive development. General measures of intelligence can be useful as a basis for diagnosis and prediction, but have less utility for the study of development. The strategy test makers use for selecting items dictates that a normal individual's score will hover at the same level over time. Moreover, an exploration of genetic and environmental influences on a general measure of intelligence reveals robust but undifferentiated effects. This mix of influences can be broken down in the context of specific measures: for example, there is strong genetic influence on nonverbal performance, strong environmental influence on receptive language, and both genetic and environmental influence on expressive language. We believe that this multifaceted approach offers the most interesting view of behavioral development.