Developmental critical periods—windows of heightened sensitivity for language acquisition, absolute pitch, visual development, and other capacities—are conventionally attributed to neural plasticity: synaptic density peaks and pruning occurs within genetically determined time windows. This paper offers an alternative interpretation through ACAT: critical periods are not primarily windows of neural plasticity but windows of verbatim absence. Before the critical period closes, the child processes inputs without pre-existing verbatim templates. Sound is processed as frequency gist, not as 'do-re-mi' symbol verbatim. Visual input is processed as spatial gist, not as labeled categories. This verbatim-free processing enables direct gist extraction at depths that are progressively blocked as verbatim templates accumulate. The critical period does not close because plasticity declines. It closes because verbatim accumulates to the point where it occludes direct gist extraction. Educational implications are profound: the optimal developmental sequence is gist-first, verbatim-later—the exact reverse of current practice.