 Speed is arguably the mark of modularity that requires least in the way of explication. But speed is relative, so the best way to proceed here is by way of examples. Speech shadowing is generally considered to be very fast, with typical lag times on the order of about 250 ms. Since the syllabic rate of normal speech is about 4 syllables per second, this suggests that shadowers are processing the stimulus in syllabus-length bits—probably the smallest bits that can be identified in the speech stream, given that “only at the level of the syllable do we begin to find stretches of wave form whose acoustic properties are at all reliably related to their linguistic values” (Fodor, 1983, p. 62). Similarly impressive results are available for vision: in a rapid serial visual presentation task (matching picture to description), subjects were 70% accurate at 125 ms. exposure per picture and 96% accurate at 167 ms. (Fodor, 1983, p. 63). In general, a cognitive process counts as fast in Fodor’s book if it takes place in a half second or less.