Processing the Np-versus S-coordination Ambiguity: Thematic Information Does Not Completely Eliminate Processing Difficulty

When faced with the NPversus S-coordination ambiguity as in, for example, The thief shot the jeweler and the cop ..., readers prefer the reading with NP-coordination (e.g., "The thief shot the jeweler and the cop yesterday") over one with two conjoined sentences (e.g., "The thief shot the jeweler and the cop panicked"). A corpus study is presented showing that NP-coordinations are produced far more often than S-coordinations, which in frequency-based accounts of parsing might be taken to explain the NP-coordination preference. However, frequency differences only become apparent when coarse-grained measures are considered. We also describe an eye tracking experiment investigating how temporarily ambiguous S-coordinated sentences are actually processed, and, more importantly, how information regarding thematic fit is used by the parser in this kind of structure. The S-coordinated sentences such as Jasper sanded the board and the carpenter laughed that were tested in the present experiment, were predicted to cause only minimal processing difficulty, if any, because of the poor thematic fit between carpenter and sanded arguing against NP-coordination. Our results indicate that information regarding poor thematic fit was used rapidly, but not without leaving some residual processing difficulty. This is compatible with claims that thematic information can reduce but not completely eliminate garden-path effects.