Halford, Wilson & Phillips argue that cognitive development is driven by increases in processing capacity. We suggest that changes in relational knowledge are as important or more so. We present evidence that 3-year-olds' analogical abilities are sharply improved by teaching them relational labels; over a 30-minute experimental session children gained approximately 2 years in effective performance. These results mandate caution interpreting age-related change as indicating maturational change, and call for a deeper consideration of the role of epistemological change in cognitive development.