Syntactic category disambiguation within an architecture of human language processing

Syntactic category disambiguation within an architecture of human language processing Peter Baumann (baumann@u.northwestern.edu) Northwestern University Department of Linguistics, 2016 Sheridan Road Evanston, IL 60208, USA Abstract for constraint-based models can also be accounted for un- der a modular architecture with a module for bottom-up syntactic category assignment. In this paper, we follow Corley and Crocker’s proposal and provide further evi- dence for the existence of a syntactic category module by showing that Corley and Crocker’s model of syntac- tic category disambiguation is a significant predictor of reading times in naturally occurring texts. In addition, we provide evidence that syntactic category disambigua- tion may be independent of syntactic top-down expec- tations, emphasizing the critical role of bottom-up pro- cesses within a modular architecture of human language processing. Syntactic category ambiguities are very frequent in nat- ural languages, and all architectures of language process- ing need a mechanism for disambiguating syntactic cat- egory ambiguities. Corley and Crocker (2000) suggested that syntactic category disambiguation can be assigned its own module within a modular architecture. We will show that the model defined by Corley and Crocker can account for a considerable amount of variance in read- ing times of naturally occurring texts. In addition, we provide evidence that syntactic category disambiguation may be independent of syntactic top-down expectations, emphasizing the important role of bottom-up processes within an architecture of human language processing. Keywords: sentence processing; reading; eye-tracking; ambiguity; lexical access. Syntactic Category Ambiguity Introduction Successful language processing requires the integration of bottom-up information extracted from the current input and top-down expectations generated from what has been processed so far. When and how bottom-up and top-down processes interact has been a distinguish- ing feature of different processing architectures. On the one hand, there are constraint-based models (e.g. Mac- Donald, Pearlmutter, & Seidenberg, 1994; Trueswell & Tanenhaus, 1994; Tabor, Juliano, & Tanenhaus, 1997), which assume one single processing unit, in which all available information is considered simultaneously. Mod- ular architectures, on the other hand, consist of several distinct processing modules (e.g. Frazier, 1987; Frazier & Clifton, 1996; Corley & Crocker, 2000). These mod- ules are restricted to each having its own internal rep- resentation, and they are independently predictive and informationally encapsulated (Crocker & Corley, 2002). Assuming this definition of modules in terms of informa- tion flow, bottom-up processes are more likely to be mod- ular than top-down processes (Appelbaum, 1998; Fodor, One particular process, for which constraint-based and modular models make contradicting predictions, is syntactic category assignment or disambiguation: constraint-based models assume that rich contextual in- formation is utilized to determine the syntactic category (i.e part of speech) of a word, while modular architec- tures only allow context-independent information. Al- though previous research may seem to have provided ev- idence for both positions, Corley and Crocker (2000) (see also Gibson, 2006) have shown that most of the evidence Many words in English (and presumably all other lan- guages) are ambiguous, they can have different senses and/or belong to different syntactic categories or part- of-speech (i.e. noun, verb, adjective, etc.). The following example (from Boland, 1997) illustrates these ambigui- ties: a. b. I saw her duck . . . . . . under the porch to eat some potato chips. . . . under the porch eat some potato chips In (1), the word duck is ambiguous between its verb and noun readings, and only the following context can disam- biguate between the two syntactic categories and senses. Syntactic category ambiguity and lexical ambiguity (in terms of different senses) need not come together like in (1). Lexical ambiguity often occurs within the same syn- tactic category as in the word cabinet, which as a noun can denote either a group of advisors or a closet. Syn- tactic category ambiguity, on the other hand, does not require lexical ambiguity, as evidenced by the English verbal system, where for all regular verbs there is only one form for the past-tense and the past-participle. This ambiguity is crucial to many garden-path sentences. The horse raced past the barn fell. The horse ridden past the barn fell. While example (2) is a classical garden-path sentence, which upon first encounter may be nearly impossible to understand, example (3) is unambiguous and relatively easy to process. The fact that example (2) is derived