The repetition effect refers to the finding that the speed and accuracy of naming a visually presented word is enhanced by a single prior presentation of the word. A new technique was developed to study this phenomenon: The visual signal-to-noise ratio of a printed item in a field of masks was slowly increased. When accuracy was of interest, the increase ceased at a predetermined time; when latency was of interest, the increase continued until the printed item could be named. Experiment 1 tested the validity of the new accuracy technique against a more traditional threshold measure of ease of identification, in which the item is presented for a single brief exposure, followed by a mask. When performance levels at the first presentation were equated for the two techniques and for both words and nonwords, the repetition effect was equal for the techniques and slightly stronger for words than for nonwords. In Experiment la psychometric functions for first presentations were obtained, giving accuracy as a function of final exposure duration. A large interaction was seen with the traditional technique yielding superior performance for words than the new technique, but the reverse was true for nonwords. In Experiment 2 the latency version of the new technique was used: The difference in'the latencies necessary for word and nonword identification was found to be additive to the difference due to repeated presentations. Taken together, the results of the experiments suggest separate contributions of lexical status and presentations to the repetition effect. Experiment 2 used separate groups for words and nonwords, but the word-nonword difference was, if anything, increased when mixed lists of words and nonwords were used in Experiment 3. This result rules out certain guessing bias interpretations of the word-nonword differences. In Experiments 1,2, and 5, lag between repetitions had at most a small and nonsignificant effect on identification accuracy and latency. However, in Experiment 5, lag between repetitions had a large effect on recognition on performance. In Experiments 1 and 3, shifting case between presentations of identical items produced a very small decrease in the repetition effect, suggesting a minimal role for low-level physical features in the repetition effect. In Experiments 2 and 4, orthographic similarity (i.e., spelling overlap) of new items to previously presented items not sharing a common morpheme was studied. A small (sometimes significant) facilitation of identification of such new items was observed. This result suggests that letter-name clusters play some role in the repetition effect. A model was developed that outlines the relative contributions of episodic traces for particular events, and of uriitized representations of words in semantic memory, to the repetition effect in word and nonword identification. The unitization that characterizes identification of words and that is missing for nonwords plays a prominent role in the model. Specifically, the repetition effect is attributed to the pr...

The studies presented in this article investigate the memory processes that underlie two phenomena in threshold identification: word superiority over pseudowords and the repetition effect (a prior presentation of an item facilitates later identification of that item). Codification (i.e., the development of a single memory code that can be triggered even by fragmented input information) explains the faster and more accurate identification of words than pseudowords. Our studies trace the development and retention of such codes for repeated pseudowords and examine the growth and loss of the repetition effect for both pseudowords and words. After approximately five prior occurrences, words and pseudowords are identified equally accurately in two types of threshold identification tasks, suggesting codification has been completed for pseudowords. Although the initial word advantage disappears, the accuracy of identification still increases with repetitions. The facilitation caused by repetition is not affected much by spacing within a session, but drops from one day to the next, and after a delay of one year has disappeared (new and old words were identified equally well). These results suggest an episodic basis for the repetition effect. Most important, after one year, performance is equal for old pseudowords and new and old words: all these levels are superior to that for new pseudowords, suggesting that the learned codes for pseudowords are as strong and permanent as the codes for words. A model of identification is presented in which feedback from codes and episodic images in memory facilitates letter processing. An instantiation of the model accounts for the major features of the data.

Three experiments were performed that compared recall for synthetic and natural lists of monosyllabic words. In the first experiment, presentation intervals of 1, 2, and 5 s per word were used. Although free recall was consistently poorer overall for the synthetic lists at all presentation rates, the decrement for synthetic stimuli did not increase differentially with faster rates. In a second experiment, zero, three, and six digits were presented visually for retention prior to free recall of each spoken word list in a preload paradigm. Fewer subjects were able to correctly recall all of the digits for the six-digit list than the three-digit list when the following word lists were synthetic. The third experiment required ordered recall of lists of natural and synthetic words. Differences in ordered recall between the synthetic and natural word lists were substantially larger for the primacy portion of the serial position curve than the recency portion. These results indicate that difficulties observed in the perception and comprehension of synthetic speech are due, in part, to increased processing demands in short-term memory. Allen (1976) and Nickerson (1975) have suggested that prosodic differences between synthetic and natural speech present the major difficulty to the comprehension of synthetic speech, particularly fluent synthetic speech. In natural speech, intensity, relative durations of segments and words, and changes in pitch are modulated by a complex set of physiological, phonetic, and linguistic factors that are as yet poorly understood (see Klatt, 1976). To attain

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