Punctuated Parsing: Signposts Along the Garden-Path

Although there has been some speculation concerning the role played by punctuation in parsing, there has been amazingly little empirical investigation of the issue. Punctuation appears to be a widely neglected topic. For the most part, where punctuation has been included in parsing studies, investigators have simply assumed that punctuation, such as commas, can be used to effectively disambiguate ’garden path’ sentences. There has been little or no consideration of how this ’disambiguation’ might occur or whether it is equally effective across different structures. The studies reported here examined whether punctuation, in the form of commas, provides an effective structural cue for the disambiguation of a variety of "Garden Path" sentences. The on-line reading time of words in three locally ambiguous sentence types, with and without the insertion of commas, was monitored using a self-paced, cumulative presentation reading technique. The studies replicated the commonly-found garden-path effects in unpunctuated prepositional phrase, relative clause, and closure ambiguities. The insertion of commas showed clear immediate effects on reading time and on the presence or otherwise of a ’garden path’ effect, but not equivalently so across the three sentence types. In line with previous research, the difficulty associated with Early Closure items was completely removed by the insertion of commas. Importantly, the parsing of the preferred Late Closure structure was unaffected by appropriate commaing. Similarly, the problem with the parsing of even ’difficult’ reduced relative clause structures was obliterated by the use of commas, although commas had no effect on the parsing of the unambiguous unreduced versions. In contrast, commas showed little evidence of an effect on the parsing of prepositional phrase ambiguities. These findings are discussed in relation to theories about the role played by punctuation in parsing and the extent of the parallels which can be drawn between the effects of punctuation and prosody. Participants in the studies also completed a questionnaire that examined both their opinions about the role played by punctuation generally and in the experiment they had just completed. The results showed, despite the consistent on-line effects, little conscious awareness of punctuation in the experiment and a diversity of opinion as to its appropriate use. Overall, the findings suggest that, while commas are much neglected, they provide a primary source of syntactic information that produces an immediate effect on parsing.