The most widely used formal approach to culture, the cultural consensus theory (CCT) of Romney, Weller, and Batchelder, originally relied on a priori definitions of cultural groups to map their unity and diversity. Retaining key features of classical CCT, we provide techniques to identify two or more cultural subgroups in a sample, whether those…

Background: Substantial development in social communication skills occurs in the first two years of life. Growth should be evident in sharing emotion and eye gaze; rate of communication, communicating for a variety of functions; using gestures, sounds and words; understanding language, and using functional and pretend actions with objects in play.…