In his paper, in this journal, Sterelney claims that cases of extended mind are limiting cases of environmental scaffolding and that a niche construction model is a more helpful, general framework for understanding human action. He further claims that extended mind cases fit into a corner of a 3D space of environmental scaffolds of cognitive competence. He identifies three dimensions which determine where a resource fits into this space and suggests that extended mind models seem plausible when a resource is (...) highly reliable, individualised/entrenched and a single-user resource. Sterelney also claims that the most important cognition-enhancing resources are provided collectively by one generation to the next. In this paper, I argue that Sterelney is both right and wrong and this because he focuses primarily on external, physical resources and construes scaffolding as exclusively unidirectional and diachronic. Using examples of unfamiliar tool use, visual processing and human emotional ontogenesis, I argue, respectively, that extended mind cases include those which fail to meet Sterelney’s dimensional criteria; that the most important cognition—enhancing resources are those which actually build brains; that these are provided on a one-to-one basis in emotional ontogenesis; and, this depends on bidirectional and synchronic cognitive scaffolding. (shrink)