Potassium-adenosine triphosphate complex: values of and uses for its formation constant.

tem altogether, in contrast to our alphabet, which maps (at least in large part) into the level of phonemes. What is the critical feature of the difference between the Chinese logographic and the English alphabetic system which leads to reading difficulty? It could be the complete absence of sound mapping in Chinese; it could be the particular properties of the phoneme, rather than sound mapping per se; or it could be the irregularities of the grapheme to phoneme mapping in English. We suspect that the phonemic representation contributes most heavily to reading difficulty. We and many others have found that children with reading backwardness have difficulty in "constructing" words from these isolated sounds. There is further evidence both from speech output (articulation) and input (perception) that the alphabetic unit or phoneme is unnatural or at least highly abstract (11). If our suspicions are correct, then some unit intermediate between the morpheme and the phoneme-for example, the syllable-might be more suitable as a vehicle for introducing reading. An efficient orthography must satisfy only two requirements. It must be easy to learn and it must be productive in the sense that, after mastery, new words can be read without learning new symbols. Hence, the ultimate unworkability of the whole word method (12). The syllabary may meet these requirements (13). It has the advantage of pronounceableness (many phonemes cannot be pronounced in isolation) but still maintains its productivity or openendedness. It may therefore be a good step on the road toward learning to read alphabetic writing (14). PAUL ROZIN SUSAN PORITSKY RAINA SOTSKY Department of Psychology, University of Pennsylvania, Philadelphia 19104