Do beez buzz? Rule-based and frequency-based knowledge in learning to spell plural -s

There has been much discussion about whether certain aspects of human learning depend on the abstraction of rules or on the acquisition of frequency-based knowledge. It has usually been agreed, however, that the spelling of morphological patterns in English (e.g., past tense -ed) and other languages is based on the acquisition of morphological rules, and that these rules take a long time to learn. The regular plural -s ending seems to be an exception: Even young children can spell this correctly, even when it is pronounced /z/ (as in bees). Reported here are 3 studies that show that 5- to 9-year-old children and adults do not usually base their spellings of plural real-word and pseudo-word endings on the morphological rule that all regular plurals are spelled with -s. Instead, participants appeared to use their knowledge of complex but untaught spelling patterns, which is based on the frequency with which certain letters co-occur in written English.