The on-line study of sentence comprehension: an examination of dual task paradigms.

This paper presents three studies which examine the susceptibility of sentence comprehension to intrusion by extra-sentential probe words in two on-line dual-task techniques commonly used to study sentence processing: the cross-modal lexical priming paradigm and the unimodal all-visual lexical priming paradigm. It provides both a general review and a direct empirical examination of the effects of task-demand in the on-line study of sentence comprehension. In all three studies, sentential materials were presented to participants together with a target probe word which constituted either a better or a worse continuation of the sentence at a point at which it was presented. Materials were identical for all three studies. The manner of presentation of the sentence materials was, however, manipulated; presentation was either visual, auditory (normal rate) or auditory (slow rate). The results demonstrate that a technique in which a visual target probe interrupts ongoing sentence processing (such as occurs in unimodal visual presentation and in very slow auditory sentence presentation) encourages the integration of the probe word into the on-going sentence. Thus, when using such 'sentence interrupting' techniques, additional care to equate probes is necessary. Importantly, however, the results provide strong evidence that the standard use of fluent cross-modality sentence investigation methods are immune from such external probe word intrusions into ongoing sentence processing and are thus accurately reflect underlying comprehension processes.