Orthographic depth

The orthographic depth of an alphabetic orthography indicates the degree to which it deviates from simple one-to-one letter-phoneme correspondence.

Orthographies may be defined as either shallow or deep, depending on the ease of predicting the pronunciation of a word from its spelling. In shallow orthographies, the spelling-sound correspondence is direct: given the rules anyone can immediately "name" the words correctly (Besner & Smith, 1992, p.45). In other words,Shallow orthographies have a one-to-one relationship between graphemes and phonemes, and the spelling of words is very consistent. A shallow orthography is also sometimes called a phonemic orthography. In contrast, in deep orthographies the relationship is less direct, and reader must learn the arbitrary or unusual pronunciations of irregular words (Besner & Smith, 1992, p.45). In other words, Deep orthographies are writing systems that do not have a one-to-one correspondence between sounds (phonemes) and the letters (graphemes) that represent them.

According to orthographic depth hypothesis, shallow orthographies are more easily able to support a word recognition process that involves the language phonology. In contrast, deep orthographies encourage a reader to process printed words by referring to their morphology via the printed word's visual-orthographic structure (Katz & Frost, 1992,71). For languages with relatively deep orthographies, such as English, French, Chinese, Arabic or Hebrew, new readers have a great deal more difficulty learning to decode words. As a result, children learn to read more slowly.

For languages with relatively shallow orthographies, such as Esperanto, Italian and Finnish, new readers have few problems learning to decode words. As a result, children learn to read relatively quickly. The phonetic writing systems of Japanese (hiragana and katakana) are another example of shallow orthography, but Japanese also uses logographs (kanji), which is significantly more complicated, and requires long study to master.

Bosch et al. consider orthographic depth to be the composition of at least two separate components. One of these relates to the complexity of the relations between the elements at the graphemic level (graphemes) to those at the phonemic level (phonemes), i.e. how difficult it is to convert graphemic strings (words) to phonemic strings. The second component is related to the diversity at the graphemic level, and to the complexity of determining the graphemic elements of a word (graphemic parsing), i.e., how to align a phonemic transcription to its spelling counterpart.