The valid identification and description of language impairment in children who speak African American English (AAE) has been a major clinical challenge for over 30 years. This challenge centers on the issue of "deficit" versus "difference" for language features that contrast with Standard American English. The distinction between "deficit" and "difference" in identifying language disorders in child African American English speakers is the key to valid language assessment in AAE. Most syntactic targets in SAE are presumably invariable while many syntactic targets in AAE are variable. For example, the SAE target syntactic form for the copula "is" would be represented by "He is bad". Whereas that same production in AAE might yield either "He is bad" or "He_bad". Our research focuses on how one determines if a child AAE speaker who uses "He_bad" does so as a function of dialect, not impairment.