ON THE CHARACTERIZATION OF A CHAIN SHIFT IN NORMAL AND DELAYED PHONOLOGICAL ACQUISITION

Several theoretical and descriptive challenges are presented by childr en's phonological substitution errors which interact to yield the effe ct of a chain shift. Drawing on an archival study of the sound systems of five children (ages 3;5 to 4;0) with normal development and 47 chi ldren (ages 3;4 to 6;8) with phonological delay, one such chain shift, namely the replacement of target /theta/ by [f] and the replacement o f /s/ by [theta], was identified in the speech of six children from th e two subgroups. Different derivational and constraint-based accounts of the chain shift were formulated and evaluated against the facts of change and the children's presumed perceptual abilities. An adequate a ccount in either framework was found to require the postulation of und erspecified and, in some instances, nonadult-like underlying represent ations. Such representations were able to reconcile within a single-le xicon model the presumed production/perception dilemma commonly associ ated with acquisition. Continuity was also preserved by limiting under lying change to just those lexical items which exhibited a change phon etically.