Children's differing learning trajectories cross-linguistically have been at the forefront of gender acquisition research, often with conflicting results and conclusions. As a result, the source of children's different learning behaviors in gender acquisition has been unclear. I argue that children's gender acquisition is driven by the search for productive patterns. First, I provide corpus studies where the predictions of a learning model (Yang, 2016) are formulated. Second, I report the results of an elicited production task on Icelandic-speaking children (N = 26, ages 2;6-6;3 years) and adults (N = 18) that puts these predictions to test. The results suggest that Icelandic-speaking children and adults draw a categorical distinction between productive and unproductive suffixes in Icelandic gender assignment. I discuss the implications of these findings for morphological learning beyond gender acquisition.