Brahmi-derived scripts, script layout, and segmental awareness

In earlier work (Sproat 2000), I characterized the layout of symbols in a script in terms of a calculus involving two dimensional catenation operators: I claimed that leftwards, rightwards, upwards, downwards and surrounding catenation are sufficient to describe the layout of any script. In the first half of this paper I analyze four Indic alphasyllabaries — Devanagari, Oriya, Kannada and Tamil — in terms of this model. A crucial claim is that despite the complexities of layout in alphasyllabic scripts, they are essentially no different in nature than alphabetic scripts, such as Latin. The second part of the paper explores implications of this view for theories of phonology and human processing of orthography. Apparently problematic is evidence that “phonemic awareness” — the ability for literate speakers to manipulate sounds consciously at the phoneme level — is much stronger with alphabetic scripts, than with alphasyllabaries. But phonemic awareness is not categorically absent for readers of Indic scripts; in general, how aware a reader is of a particular phoneme is related to how that phoneme is rendered in the script. Relevant factors appear to include whether the symbol is written inline, whether it is a diacritic, and whether it is ligatured with another symbol.