In order to understand proposition 1 historically, we have to examine the patterns of change across frames within dyads. We illustrate these historical patterns and interdyad differences with a quantitative description of frames and transitions for the four representative dyads that will be used for the qualitative analysis, followed by a detailed qualitative description of the historical processes with each dyad. In this chapter, we focus on the first of the four representative dyads, Richard and his mother. In Chapters 9–11, we review the other three representative dyads respectively. In this chapter, we also give an overview of the analytical approach.

Our criterion for selecting the four dyads was based on the development of interdyad differences. We chose two dyads in which the infants developed a preference for object play as judged by relatively higher durations, compared to the other research participants, of the not-guided object frame in the post-reaching period (Richard and Betsy and their mothers). We chose two comparison dyads that showed relatively lower durations in not-guided object frames, and relatively higher durations in the mixed social-object frame during the post-reach period (Lewis and Susan and their mothers). These two pairs of dyads, therefore, correspond to the interdyad differences found in the literature (see Chapter 2): dyads that are relatively more focused on object play compared to dyads that are relatively more focused on social play. Betsy and her mother were African-American and the other dyads were Caucasian-American.