This chapter demonstrates how event-related potentials (ERPs) can be used to detect, isolate, and analyze functional neural modules, with special attention to functional modularity in semantic information processing. In particular, it shows how a new method of analyzing electrophysiological data, the additive-amplitude method, combines the physical property of linear superposition of electrical fields with factorial experimental design to reveal the existence of encapsulated neurocognitive modules without relying on strong assumptions. The fact that ERPs can be measured at the scalp indicates that the conditions of synchrony, spatial proximity, and parallel geometrical configuration that enable the summation of individual neuronal electric fields must hold. The additive-amplitude method yields new insights into semantic information processing architecture. Finally, it should be noted that because the additive-amplitude method focuses on a fundamental property of mind and brain, it is applicable to a broad range of areas within psychology and neuroscience.