The Organization of Exploratory Behavior in Down Syndrome and Nondelayed Infants Robert H. MacTurk, Peter M. Vietze, Mary E. McGarthy, Susan McQuiston, and Leon J. Yarrow National Institute of Child Health and Human Development MACTURK, ROBERT H.; VIETZE, PETER M.; MCCARTHY, MARY E.; MCQUISTON, SUSAN; and YARROW, LEON J. The Organization of Exploratory Behavior in Down Syndrome and Nondelayed Infants. CHILD DEVELOPMENT, 1985, 56, 573-581. The exploratory behaviors of a sample of 11 infants with Down syndrome and 11 nondelayed infants, matched on Bayley mental raw scores and gender, were analyzed. Transitional probabilities and z scores were computed for each possible behavior change as well as Irequencies of each behavior. The analyses revealed significant differences in how the 2 samples distribute their exploratory activities. The significant transitional probabilities among the 6 behavioral states revealed a pattem of similarities and differences. In general, both groups of infants organized their exploratory activities in a similar manner. However, there were differences that appeared to depend on the level of exploratory sophistication. The results are discussed in the context of the similarities and differences between the samples. For a long time, exploratory behavior during infancy has been regarded as the cen- ter;piece for the development of competence. Piaget (1952) saw exploration as an integra- tive process, while White (1959) considered it to be the mechanism by which infants express their motivation to master the environment. In a more empirical framework, McCall (1974) examined the developmental parame- ters of exploratory behaviors and, with his as- sociates (McCall, Eichom, & Hogarty, 1977; Weisler & McCall, 1976), demonstrated that early exploratory behaviors were an important contributor to later competence. Recent studies have focused on extend- ing McCall's (1974) notion that exploration is made up of discrete behaviors that follow a developmental progression toward greater sophistication and abstraction. Much of this work has been summarized by Belsky and his associates (Belsky, Carduque, & Hmcir, 1984; Belsky & Most, 1981), who developed a tax- onomy that charts the development of explor- atory behaviors through the first 2 years of life, from indiscriminate mouthing to sophis- ticated symbolic play. The emphasis to date has been on defining age-characteristic modes of explora- tion and establishing their developmental se- quence. What has not been examined is how infants organize their exploratory activities. Civen that young infants display a variety of exploratory behaviors, what are the se- quences of operations they employ to obtain information from inanimate objects? Though the analytic techniques for studying se- quences of behavior are well established in the ethological literature (see Sustare, 1978) and have b6en successfully applied to studies of human social interaction (Bakeman & Brown, 1977; Vietze, Abemathy, Asche, & Faulstich, 1978), fbere remains a lack of data on the sequences of exploratory behavior in infancy.' We seek to extend understanding of ex- ploratory behaviors during early infancy in the present study by examining the se- quences of manipulative interactions with ob- jects so as to shed light on the process by which infants engage with and extract infor- mation from objects. Infants were observed in a semistructured laboratory settings and their exploratory bebaviors were coded to obtain information on the transitions from one be- havior to the next (i.e., lag sequential analy- sis). In addition, the behavioral organization shown by Down syndrome (DS) and non- delayed infants was compared. Previously re- ported work (McCarthy & Vietze, 1982; Vietze, McCarthy, McQuiston, MacTurk, & We wish to acknowledge and thank David Messer, who wrote the COBOL program employed to analyze these data, and Linda Martini and Shelley Kosisky for their assistance in the preparation of this manuscript. Portions of these data were presented at the biennial meeting of the Society for Research in Child Development, Detroit, April 1983. Requests for reprints should he sent to the Child and Family Research Section, National Institute of Child Health and Human Development, Building 31, Room B2B15, Bethesda, MD 20205. [Child Development, 1985, 56, 573-581. Copyright is not claimed for this article.]