One lingering effect of William's brain damage is the presence of aphasia, mentioned by Calvin. This is dramatized by the halting effort to speak, including difficulty in finding words. In at least two instances, William employs word substitutions, known as paraphasia. The type displayed is verbal (or semantic) paraphasia: "aria" instead of "voice," and "apples" instead of "avalanche." These two word substitutions help explain some theories of how words are mapped in the brain. In the case of "aria" for "voice," the semantic "web" is based on associated meanings, and in the case of "apples" for "avalanche," the "web" is based on similar phonetic codes (the short /ae/ in word-initial position).