Similarity information versus relational information: differences in the time course of retrieval.

Two experiments are reported that examine the time course of retrieval in a sentence matching procedure. Subjects learned lists of active and passive sentences and were tested with sentences in active or passive, correct or incorrect versions; for example, if "John hit Bill" was a studied sentence, "Bill hit John" would be an incorrect active test sentence. A response signal procedure was used so that accuracy could be measured as a function of time. The data show that sentences containing words from studied sentences are discriminable early in processing from sentences containing all new words, but discrimination of correct from incorrect versions of studied sentences occurs only later in processing (after 600-700 ms). These results demonstrate that different kinds of information are available at different points during the time course of retrieval and so suggest that modifications are required of models that provide only a unitary value for the amount of match between a test probe and information in memory. Early in processing, the growth of accuracy can be explained by a simple model that assumes independent contributions to total amount of match for each of the content words of a sentence, but this independent processing model cannot account for discrimination later in processing. Several, more general, memory models are examined with respect to their abilities to produce independent item information early in processing and relational information later in processing.