The Bayley Scales of Infant and Toddler Development (BSCID; Bayley, 1969, 1993, 2006) are frequently used and well-known developmental Scales designed to measure the developmental functioning of infants and toddlers. The newest Version is the Bayley Scales of Infant and Toddler Development –Third Edition (BSCID-III, 2006). It is an individually administered instrument and is appropriate for children between the ages of 1 month and 42 months. The BSCID-III assesses developmental functioning in

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... e scales cognition, language, motor skills, social–emotional and adaptive behavior. The cognitive scale provides only general information through a cognitive composite-score. It remains unclear which aspects of cognition are being measured (Bradley-Johnson & Johnson, 2007). The aim of this diploma thesis is an analysis of the underlying cognitive abilities as well as to construct cognitive subscales based on the cognitive Scale of the BSCID-III. Therefore test-items were examined with regard to their content. The preliminary classification was refined by two experts of developmental psychology. The final classification comprised the six cognitive subscales concept formation, part-whole-hierarchy, representative thinking, imitation, problem solving and memory. A statistic evaluation supports the plausibility of the model of six cognitive subscales. The statistical analysis suggests an acceptable separation of the subscales. Further validation using independent samples is recommended to allow for ascertained detection of uncommon development in specific cognitive domains.