In this study, I provide a microgenetic-historical account of learning in an informal setting: the conceptual change that occurred while a university-based scientific research laboratory investigated the absorption of light in rod-based photoreceptors of coho salmon, which the "dogma" had suggested to be related to the migration between freshwater and saltwater environments. A morphogenetic, catastrophe theoretic model is proposed and used to structure the account of the conceptual change. The data derive from a 5-year video-based ethnographic study of the laboratory and the fish hatcheries that supplied it with hatchery-raised and wild coho at different developmental stages. Because the scientists collected their data over a 2-year period, slowing down the availability of what they would be saying were their complete data, opportunities arose for studying the conceptual change ethnographically. The study reports difficulties scientists encountered interpreting their data-because they (a) took a dogma-related perspective, (b) had to reconstruct and become familiar with the context from which they had abstracted their specimen, (c) required a biologically relevant rather than mathematically plausible explanation, and (d) exhibited aspect blindness that only disappeared as their familiarity increased.