Patterns of assistance in parent-child dyads were examined by developing measures that could be used to explore the nature of assistance and learner action sequences. A microgenetic approach was adopted in a teaching experiment that may be regarded as a variation of the double stimulation method of L. S. Vygotsky. A second goal was to explore the blending of quantitative, multivariate methods with interpretive methods in advancing the cultural-historical (CH) model. Thirty-two fourth to sixth graders and their mothers from the United States and 32 such pairs from Peru were studied. Parent-child problem solving activity was observed in a laboratory setting where interactions during a categorization task were videotaped. In one study process measures were the focus and in another assistance patterns were examined as a function of children's developmental level, analyzing the relationship between negotiation in the children's zone of proximal development and resulting assisted responses. Findings suggest that the factor score for a given dyad is a prevailing characteristic of a given family setting. Interaction patterns were moderately correlated with a distant measure of development. The combination of research methods is useful in understanding the nature and nurture of cognitive environments. Three tables present study findings. (SLD)