This article questions how two very similar sets of experiments can yield such very different findings, and comments on the differences between the studies. Here Annamarie Kerkhoff presents a commentary on some perceived differences between the studies in areas such as age groups and group sizes evaluated. Kerkhoff also comments on some differences in methodology, possibly resulting in additional processing load for the Boloh & Ibernon experiments, in which three rather than two colour coded objects were coupled with three bags of different sizes in a story context, while Karmiloff-Smith only had children comment on a simple action. Another likely reason for the different findings is the difference in stimuli. Kerkhoff argues that all in all, the evidence seems less clear-cut than the authors of the studies present it to be, in line with a more gradient notion of productivity based on input patterns.