Chapter 22 - Commas and Spaces: Effects of Punctuation on Eye Movements and Sentence Parsing

Robin L. Hill, Wayne S. Murray

Research output: Chapter in Book/Report/Conference proceedingChapter


While it has been widely assumed that punctuation may play a critical role in reading, there has been relatively little direct empirical investigation of its effects on the process in general or eye movements in particular. Most research on sentence parsing has either avoided the use of punctuation or simply assumed that it necessarily serves a disambiguating role. There has been little or no consideration of how ‘disambiguation’ might occur or of the precise nature of the effects that punctuation might have on the reading process. Previous work using self-paced reading (Hill and Murray, 1997a, b) has in fact shown that simplistic assumptions related to the disambiguating effect of punctuation cannot be supported. These studies demonstrated that while punctuation plays a potent disambiguating role in some structures, the effect is by no means universal. It remained unclear, however, whether these conclusions could be generalised to a more natural reading situation and whether eye-movement patterns while reading punctuated text provide an insight into the underlying parsing mechanisms. In this chapter we discuss more recent studies which have extended this work by monitoring subjects’ eye movements while reading exemplars of three types of locally ambiguous items with and without inserted punctuation. In order to control for simple oculomotor effects related to the additional spacing associated with punctuation, the studies also included a condition with equivalent spacing but without punctuation. The results show potent effects of punctuation on the first-pass processing of two structures (early-closure and reduced relative-clause constructions), but not in the ‘preferred’ versions of either of these and not in sentences containing prepositional phrase ambiguities. Punctuation also exerted effects on local processing difficulty, suggesting that it cues parsing decisions at particular points in a sentence. Frequently, inserted punctuation increased processing time on sections of a sentence immediately preceding a comma, while facilitating the processing which followed. The focus of this chapter, however, is on the effects of punctuation on eye-movement parameters in punctuated and unpunctuated sentences, the ways in which these differ from unpunctuated sentences with equivalent spacing and the extent to which they reflect the processing consequences of punctuation and spacing. It was found that punctuation and increased spacing between words had similar effects on the pattern of eye movements with increases in saccade extent of more than the added character space, but this similarity was not mirrored in equivalent effects on reading time and disambiguation. Punctuation therefore appears to convey information related to structure that is more potent than the simple ‘chunking’ of text, but this effect is limited to particular structural conditions. The results also suggest a dissociation between some eye-movement parameters and their consequences for underlying sentence processing.
Original languageEnglish
Title of host publicationReading as a Perceptual Process
EditorsAlan Kennedy, Ralph Radach, Dieter Heller, Joël Pynte
Place of PublicationOxford
PublisherElsevier North-Holland, Inc.
Number of pages25
ISBN (Print)978-0-08-043642-5
Publication statusPublished - 2000


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