Morphological decomposition

A wealth of psycholinguistic evidence has shown that words, before being visually recognized, decompose into smaller units which seem to correspond to morphemes (Rastle et al., 2000, 2004). Such a procedure of morphological decomposition seems to occur in words that are made of more than one morpheme, independently of whether they are semantically transparent (e.g., driver, which means “someone who drives”) or not (e.g., brother, which does not mean “someone who broths”). Decomposition, however, does not seem to occur in words that contain a root plus an additional, non-morphemic string (e.g., brothel, where el is not an English suffix). Current models of visual word processing assume the morpho-orthographic decomposition hypothesis, whereby decomposition obligatorily relies on islands of regularity – namely, statistical orthographic regularities across letter strings, so that a string such as er is detected as a single morpho-orthographic unit, but el is not (Rastle & Davis 2008). As such, decomposition is also argued to occur at early stages of word processing and before contact with the lexicon — namely, before semantic information is accessed, so that decomposition occurs regardless of semantic transparency. In my doctoral dissertation (Petrosino 2020), I built on these findings and used the visual masked priming response to test the sensitivity of decomposition to a few higher-level linguistic properties (in addition to islands of regularities) such as syllabification, whole-word frequency, phonological conditioning, and syntactic well-formedness. The results suggested that while not being affected by syllabification and syntactic well-formedness, decomposition is indeed sensitive to whole-word lexicality and whole-word frequency. This clear-cut divide between properties that may and may not impinge on decomposition might be due to the fact that both syntactic processing (i.e., the process whereby syntactic categories and affixal restrictions are retrieved and checked) and semantic processing (i.e., the process whereby whole-word meaning is accessed) require at least two mechanisms to occur: (i) recombination of decomposed morphemes (along the lines of Taft 2004), and, eventually, (ii) access to compatible syntactic and semantic representations. Given that these are fairly complex, these representations indeed take more time to access fully, which, therefore, may not occur until after decomposition. At the face value, the fact that whole-word lexicality and wor frequency may impinge on early decomposition procedures is surprising. These two properties are generally considered to be accessed at late stages of processing and their potential implications onto decomposition seems logically contradictory, under the current theories of early decomposition: how can an early process be affected by properties that concern the whole stimulus and, as such, are accessed only at later stages? A model of early visual decomposition is proposed that is able to account for these findings without necessarily challenging the morpho-orthographic decomposition hypothesis. In this model, decomposition accesses whole-word lexicality and frequency through a multi-step mechanism that first generates multiple possible morpho-orthographic decomposition patterns of the visual stimulus and then evaluates them in parallel in order to choose the optimal candidate for activation.

The investigation above has inspired a number of follow-up studies on morphological decomposition. Click on the links below for more information!