Item frequency in probe-recognition memory search: Converging evidence for a role of item-response learning

In short-term probe-recognition tasks, observers make speeded old–new recognition judgments for items that are members of short lists. However, long-term memory (LTM) for items from previous lists influences current-list performance. The current experiment pursued the nature of these long-term influences—in particular, whether they emerged from item-familiarity or item-response-learning mechanisms. Subjects engaged in varied-mapping (VM) and consistent-mapping (CM) short-term probe-recognition tasks (e.g., Schneider & Shiffrin, Psychological Review, 84, 1–66, 1977). The key manipulation was to vary the frequency with which individual items were presented across trials. We observed a striking dissociation: Whereas increased presentation frequency led to benefits in performance for both old and new test probes in CM search, it resulted in interference effects for both old and new test probes in VM search. Formal modeling suggested that a form of item-response learning took place in both conditions: Each presentation of a test probe led to the storage of that test probe—along with its associated “old” or “new” response—as an exemplar in LTM. These item-response pairs were retrieved along with current-list items in driving observers’ old-– recognition judgments. We conclude that item-response learning is a core component of the LTM mechanisms that influence CM and VM memory search.     

Nonword repetition in lexical decision: Support for two opposing processes

We tested and confirmed the hypothesis that the prior presentation of nonwords in lexical decision is the net result of two opposing processes: (1) a relatively fast inhibitory process based on global familiarity; and (2) a relatively slow facilitatory process based on the retrieval of specific episodic information. In three studies, we manipulated speed-stress to influence the balance between the two processes. Experiment 1 showed item-specific improvement for repeated nonwords in a standard “respond-when-ready” lexical decision task. Experiment 2 used a 400-ms deadline procedure and showed performance for nonwords to be unaffected by up to four prior presentations. In Experiment 3 we used a signal-to-respond procedure with variable time intervals and found negative repetition priming for repeated nonwords. These results can be accounted for by dual-process models of lexical decision (e.g., Balota & Chumbley, 1984; Balota & Spieler, 1999).     

Can attention be allocated to sensory modalities?

Three experiments examined the effects of attention allocation to the modalities of vision, audition, and touch. The first two experiments utilized a simultaneous-successive comparison. The simultaneous procedure involved simultaneous monitoring of all three sensory modalities for the presence of a near-threshold stimulus. The successive condition allowed S to give his full attention to each sensory modality in turn. There was no advantage for the successive condition, whether the task consisted of detection of a single stimulus (Experiment I) or detection of the absence of one of many stimuli (Experiment II). Experiment III used a different paradigm to extend these results and bridge the gap between these results, those of Eijkman and Vendrik (1965), and those of Moray (1973a, b). We concluded that selective allocation of attention to sensory modalities does not affect the early stages of perceptual processing.     

On the degree of attention and capacity limitation in tactile processing

Two conditions were used to evaluate Os’ ability to detect near-threshold vibrotactile stimuli. In both conditions, a signal was presented at one of three skin loci, the O stating which locus received the stimulus. In the simultaneous condition, there was a single observation interval during which a signal occurred at one of the three loci. In the sequential condition, there were three observation intervals presented successively at 800-msec intervals, with a signal presented at one of the three loci during one of the three observation intervals. Each observation interval was associated with a particular locus. Theories postulating attentional control and limitations of capacity during this type of vibrotactile information processing predict performance to be inferior in the simultaneous condition, since that condition requires sharing of attention among the three possible sources of tactile stimulation. The data showed performance to be identical in the two conditions. This result not only disconfirms the single-channel model proposed by Franzen, Markowitz, and Swets (1970), but also argues for an unlimited-capacity nonattention model of tactile perceptual processing. The results are in accord with similar findings for visual processing by Shiffrin and Gardner (1972).     

Building permanent memory codes: codification and repetition effects in word identification

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.     

Turning up the noise or turning down the volume? On the nature of the impairment of episodic recognition memory by midazolam

E. Hirshman, J. Fisher, T. Henthom, J. Amdt, and A. Passanname (2002) found that Midazolam disrupts the mirror-patterned word-frequency effect for recognition memory by reversing the typical hit-rate advantage for low-frequency words. They noted that this result is consistent with dual-process accounts (e.g., R. C. Atkinson & J. F. Juola, 1974; G. Mandler, 1980; A. P. Yonelinas, 1994) of the word frequency effect for recognition memory (S. Joordens & W. E. Hockley. 2000; L. M. Reder et al. 2000). The present authors show that this finding is also consistent with a variety of single-process, retrieving effectively- from-memory (REM) models (R. M. Shiffrin & M. Steyvers, 1997), the simplest of which assumes that Midazolam decreases the accuracy with which memory traces are stored. These findings therefore do not discriminate between single- and dual-process models of recognition memory.     

Visual noise reveals category representations

How are categories represented in human memory? Exemplar models assume that a category is represented by individual instances from that category that have been experienced. More generally, a category might be represented by multiple templates stored in memory. A new item is classified according to its similarity to these templates.Prototype models represent a category with a single summary abstraction (i.e., a single template), often the central tendency of the experienced items. A new item is classified according to its similarity to these category prototypes. Here, we show how a technique for correlating observers’ responses with external noise can be used not only to distinguish single- from multiple-template representations, but also to induce the form of these templates. The technique is applied to two tasks requiring categorization of simple visual patterns; the results demonstrate that observers used multiple traces to represent their categories, and thus highlight the procedure’s potential for use in more complex settings.     

A model for evidence accumulation in the lexical decision task

We present a new model for lexical decision, REM-LD, that is based on REM theory (e.g., ). REM-LD uses a principled (i.e., Bayes' rule) decision process that simultaneously considers the diagnosticity of the evidence for the 'WORD' response and the 'NONWORD' response. The model calculates the odds ratio that the presented stimulus is a word or a nonword by averaging likelihood ratios for lexical entries from a small neighborhood of similar words. We report two experiments that used a signal-to-respond paradigm to obtain information about the time course of lexical processing. Experiment 1 verified the prediction of the model that the frequency of the word stimuli affects performance for nonword stimuli. Experiment 2 was done to study the effects of nonword lexicality, word frequency, and repetition priming and to demonstrate how REM-LD can account for the observed results. We discuss how REM-LD could be extended to account for effects of phonology such as the pseudohomophone effect, and how REM-LD can predict response times in the traditional 'respond-when-ready' paradigm.