The Geoffrey Saxe and Esmonde monograph (this issue) offers both fascinating empirical findings and intriguing theoretical insight about cultural change and individual cognition. Cultural and cognitive changes are "reciprocal processes," but how can these be related in research? One obvious way is to conduct longitudinal studies of the mutual influence between cultural-historical change and individual cognitive change by measuring the target cognition at multiple points on a historical time scale. Saxe, though his formulation is clearly historical, has adopted a different approach. His earlier work on adaptive changes in the Oksapmin body-part counting system of number due to the shift from the subsistence economy (with infrequent barter) to money economy in the Oksapmin community (Saxe, 1982) is seminal in the field of culture and cognition research. His major data were obtained from the comparison among those people who had the same cultural background but had had obviously different extent of exposure to the new economy, more specifically, the comparison among older adults, young adults, plantation returnees who had worked for an extended period outside the Oksapmin community, and trade store owners. As expected, with greater experience in the money economy, individuals increasingly used more sophisticated arithmetic strategies, though all of them still relied on the body-part sequence. In this commentary, the author examines Saxe and Esmonde's methodology and how much success the study has achieved with it.