Spelling

Success in modern literate societies requires the ability to read and write proficiently. Although the past several decades have seen a strong interest in the [Page 932]processes underlying proficient reading ability, much less research attention has been given to understanding writing. This is due in part to the fact that writing is a historically more newly acquired skill than reading and, until recently, was a skill that was mastered by few people. However, with the burgeoning of technological advances, success in many societies now requires strong literacy skills that include proficient writing skills. An important component of the writing process is spelling. The ability to produce written words easily and proficiently allows the writer to have sufficient cognitive resources available for other important aspects of writing, such as composing the message. As such, researchers have increasingly begun to focus on the structure of the spelling system and the development of spelling abilities.

Most theories of the structure of the spelling system assume that there are two independent processes responsible for the spelling of familiar and unfamiliar words: a lexical process, which is mainly responsible for spelling familiar words, and a sublexical process for spelling novel or unfamiliar words (see Figure 1). When spelling a familiar word via the lexical process, the spelling is retrieved from a long-term memory store called the orthographic lexicon. The forms in this store comprise graphemes that are abstract representations of letters that can be converted into either written or oral form in later stages. The lexical process is semantically mediated such that in order to spell a familiar word, a stored spelling is retrieved from the orthographic lexicon via semantic input, which includes information about the meaning of the word to be spelled. The abstract orthographic representation that is retrieved is kept active via a working memory process called the graphemic buffer. The buffer is responsible for keeping the orthographic information active so that serial processes can convert the abstract form into an appropriate oral (letter names) or written form (letter shapes) for output. When an unfamiliar word must be spelled, the sublexical process serially converts the oral input, which comprises phonemes (sounds), into a string of abstract letter representations (graphemes). These are then kept active by the graphemic buffer for serial output for either written or oral spelling. The sound-to-letter conversion process is guided by the frequency of phoneme-to-grapheme mappings, which indicate which sound-letter mappings are most common, as well as by contextual constraints that indicate which letter combinations are permissible and most common in a language. Recent evidence suggests that lexical and sublexical processes interact during spelling such that sublexical processes influence the output of the lexical system.

Early theories of spelling assumed that the spelling representations stored in the orthographic lexicon are linear strings containing only information about letter identities and their order. However, studies of patients with impairments to the graphemic buffer have provided evidence that orthographic representations are more complex than originally proposed. Damage at the level of the buffering process should result in errors that reflect the limitations of a working memory process: errors reflecting differences in length and letter errors such as misordering letters, deleting letters, and so on. However, some patients have produced distinctive patterns of errors that indicate that orthographic representations include not just letter identity and order, but also the consonant-vowel status of the individual letters and information about letter quantity (i.e., whether a letter is doubled). More controversially, some data suggest that information about the written syllable structure of a word is also represented. Overall, these data indicate that the long-term memory representations of words' spellings are complex, including information that goes beyond a simple listing of letters and their order.

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