Specificity of memory representations for spoken words

Many theories of spoken word recognition assume that lexical items are stored in memory as abstract representations. However, recent research (e.g., Goldinger, 1996) has suggested that representations of spoken words in memory are veridical exemplars that encode specific information, such as characteristics of the talker’s voice. If representations are exemplar based, effects of stimulus variation such as that arising from changes in the identity of the talker may have an effect on identification of and memory for spoken words. This prediction was examined for an implicit and explicit task (lexical decision and recognition, respectively). Comparable amounts of repetition priming in lexical decision were found for repeated words, regardless of whether the repetitions were in the same or in different voices. However, reaction times in the recognition task were faster if the repetition was in the same voice. These results suggest a role for both abstract and specific representations in models of spoken word recognition.     

Frequency effects in spoken and visual word recognition: evidence from dual-task methodologies

The authors report 3 dual-task experiments concerning the locus of frequency effects in word recognition. In all experiments, Task 1 entailed a simple perceptual choice and Task 2 involved lexical decision. In Experiment 1, an underadditive effect of word frequency arose for spoken words. Experiment 2 also showed underadditivity for visual lexical decision. It was concluded that word frequency exerts an influence prior to any dual-task bottleneck. A related finding in similar dual-task experiments is Task 2 response postponement at short stimulus onset asynchronies. This was explored in Experiment 3, and it was shown that response postponement was equivalent for both spoken and visual word recognition. These results imply that frequency-sensitive processes operate early and automatically.     

Phonological priming in spoken word recognition: Task effects

In two experiments, we examined the role of phonological relatedness between spoken items using both the lexical decision task and the shadowing task. In Experiment 1, words were used as primes and overlaps of zero (control), one, two, or all four or five (repetition) phonemes were compared. Except for the repetition conditions, in which facilitation was found, phonological overlap resulted in interference on word responses. These effects occurred in both tasks but were larger in lexical decision than in shadowing. The effects that were evident in shadowing can be attributed to an attentional mechanism linked to the subjects' expectancies of repetitions. The extra effects obtained in lexical decision can be interpreted by taking into account both activation of the response corresponding to the prime's lexical status and postlexical processes that check for phonological congruency between prime and target. In Experiment 2, some modifications were introduced to prevent the involvement of strategic factors, and pseudowords were used as primes. No effect at all was observed in shadowing, whereas in lexical decision interference effects occurred, which is consistent with the hypothesis that lexical decision may be negatively affected by finding a phonological discrepancy at the same time as the primed response is reactivated. Neither experiment provided evidence for the occurrence of phonological priming in the perceptual processing of words.     

Audiovisual speech facilitates voice learning

In this research, we investigated the effects of voice and face information on the perceptual learning of talkers and on long-term memory for spoken words. In the first phase, listeners were trained over several days to identify voices from words presented auditorily or audiovisually. The training data showed that visual information about speakers enhanced voice learning, revealing cross-modal connections in talker processing akin to those observed in speech processing. In the second phase, the listeners completed an auditory or audiovisual word recognition memory test in which equal numbers of words were spoken by familiar and unfamiliar talkers. The data showed that words presented by familiar talkers were more likely to be retrieved from episodic memory, regardless of modality. Together, these findings provide new information about the representational code underlying familiar talker recognition and the role of stimulus familiarity in episodic word recognition.     

Contributions of surface and conceptual information to recognition memory

The present experiments were designed to determine whether memory for the voice in which a word is spoken is retained in a memory system that is separate from episodic memory or, instead, whether episodic memory represents both word and voice information. These two positions were evaluated by assessing the effects of study-to-test changes in voice on recognition memory after a variety of encoding tasks that varied in processing requirements. In three experiments, the subjects studied a list of words produced by six voices. The voice in which the word was spoken during a subsequent explicit recognition test was either the same as or different from the voice used in the study phase. The results showed that word recognition was affected by changes in voice after each encoding condition and that the magnitude of the voice effect was unaffected by the type of encoding task. The results suggest that spoken words are represented in long-term memory as episodic traces that contain talker-specific perceptual information.     

Repetition priming of words and pseudowords in divided attention and in amnesia

Repetition priming of novel stimuli (pseudowords) and stimuli with preexisting representations (words) was compared in two experiments. In one, 19 normal male subjects performed a lexical decision task with either focused or divided attention. In another, lexical decision performance was compared between 8 male Korsakoff patients and 8 alcoholic control subjects. In control conditions, repetition speeded responses to both stimulus types. Experimental conditions that minimized the contribution of episodic memory to task performance eliminated reaction time priming for pseudowords but not for words. However, in these same conditions, repetition increased the likelihood that pseudowords would be incorrectly classified. These results indicate that preserved repetition priming effects in amnesia do not solely reflect activation of representations in semantic memory.     

Long-term priming of neighbours biases the word recognition process: evidence from a lexical decision task.

The role of orthographically similar words (i.e., neighbours) in the word recognition process has been studied extensively using short-term priming paradigms (e.g., Colombo, 1986). Here we demonstrate that long-term effects of neighbour priming can also be obtained. Experiment 1 showed that prior study of a neighbour (e.g., TANGO) increased later lexical decision performance for similar words (e.g., MANGO), but decreased performance for similar pseudowords (e.g., LANGO). Experiment 2 replicated this bias effect and showed that the increase in lexical decision performance due to neighbour priming is selectively due to words from a relatively sparse neighbourhood. Explanations of the bias effect in terms of lexical activation and episodic memory retrieval are discussed.     

Emotional arousal enhances word repetition priming

Three experiments were conducted to determine if emotional content increases repetition priming magnitude. In the study phase of Experiment 1, participants rated high-arousing negative (taboo) words and neutral words for concreteness. In the test phase, they made lexical decision judgements for the studied words intermixed with novel words (half taboo, half neutral) and pseudowords. In Experiment 2, low-arousing negative (LAN) words were substituted for the taboo words, and in Experiment 3 all three word types were used. Results showed significant priming in all experiments, as indicated by faster reaction times for studied words than for novel words. A priming × emotion interaction was found in Experiments 1 and 3, with greater priming for taboo relative to neutral words. The LAN words in Experiments 2 and 3 showed no difference in priming magnitude relative to the other word types. These results show selective enhancement of word repetition priming by emotional arousal.     

Episodic accessibility and morphological processing: evidence from long-term auditory priming

Long-term priming studies of lexical processing have yielded conflicting claims as to whether abstract versus episodic representations are involved during word recognition. A critical piece of evidence that could separate the two accounts rests on the existence of full morphological priming, where morphologically related words yield the same amount of priming as repeated words. In this study, participants performed speeded lexical decision on lists of auditory words and non-words, which contained repeated, morphologically related, semantically related and phonologically related pairs of items. In order to minimize the involvement of episodic factors, we increased the prime-target interval and decreased their physical similarity by introducing a change in speaker’s voice. We show that under conditions that minimize access to episodic features, the magnitude of repetition priming decreased to attain that of morphological priming. Importantly, morphological and repetition priming for words were always observed in the absence of any semantic and phonological priming, suggesting that they cannot be reduced to formal or meaning overlap. Our results support the view that long-term priming taps both abstract lexical codes with a morphological format and episodic memory components. Further, they show that episodic influences on priming can be modulated by prime-target interval and physical similarity.     

An Item specific Locus of Repetition Priming

Two principal types of account of repetition priming postulate either facilitation of activation of perceptual representations used in stimulus recognition, or retrieval of specific processing episodes as possible mechanisms by which the effect occurs; these make different predictions concerning the priming of two stimuli presented simultaneously. In Experiments 1-3, subjects made same/different decisions about picture-word stimulus pairs. Recombining the pairings of a subset of items between training and test encounters did not significantly reduce the benefit in response time from repetition, as compared to pairs repeated intact. Subjects were able to remember the pairings (Experiment 4), but this did not influence repetition priming. Instead, the memory representations underlying the priming of each item in a pair were independent. No priming was found between pictures seen at training and words at test, and vice versa (Experiment 5), indicating that representations underlying the repetition effect were domain-specific. In Experiment 6, stimuli were all from within the domain of object pictures. Again, recombining the pairings of items between training and test did not significantly reduce the benefit in response time from repetition, as compared to pairs repeated intact. These results reveal an item-specific locus for repetition priming, consistent with priming occurring within pre-semantic perceptual representation systems involved in item recognition. The findings pose problems for theories that argue that repetition effects result only from retrieval of entire processing episodes.     

Guessing Strategies, Aging, and Bias Effects in Perceptual Identification

In the typical single-stimulus perceptual identification task, accuracy is improved by prior study of test words, a repetition priming benefit. There is also a cost, inasmuch as previously studied words are likely to be produced (incorrectly) as responses if the test word is orthographically similar but not identical to a studied word. In two-alternative forced-choice perceptual identification, a test word is flashed and followed by two alternatives, one of which is the correct response. When the two alternatives are orthographically similar, test words identical to previously studied items are identified more accurately than new words (a benefit) but tests words orthographically similar to studied words are identified less accurately than new words (a cost). Ratcliff and McKoon (in press) argue that these are bias effects that arise in the decision stage of word identification. We report five experiments that examined the alternative hypothesis that these bias effects arise from postperceptual guessing strategies. In single-stimulus perceptual identification, repetition priming benefits were equally great for young and older adults who claimed to use deliberate guessing strategies and those who did not (Experiment 1). In contrast, only groups of young and older people who claimed to deliberately guess studied words in a two-alternative forced-choice task (Experiments 2 and 5) showed reliable benefits and costs. Costs and benefits were abolished in the two-alternative forced-choice task when a very long study list was used, presumably because the increased retrieval burden made the use of deliberate guessing strategies less attractive (Experiment 3). Under conditions similar to those of Experiment 3, repetition priming was observed in single-stimulus perceptual identification (Experiment 4). These results are consistent with the view that costs and benefits in the forced-choice perceptual identification task arise from deliberate guessing strategies but that those in the single-stimulus task do not. The possibility that the observed relationship between strategy reports and priming effects reflects erroneous postexperimental assessments of strategies by participants is also considered.     

Examining the effects of variation in emotional tone of voice on spoken word recognition

Emotional tone of voice (ETV) is essential for optimal verbal communication. Research has found that the impact of variation in nonlinguistic features of speech on spoken word recognition differs according to a time course. In the current study, we investigated whether intratalker variation in ETV follows the same time course in two long-term repetition priming experiments. We found that intratalker variability in ETVs affected reaction times to spoken words only when processing was relatively slow and difficult, not when processing was relatively fast and easy. These results provide evidence for the use of both abstract and episodic lexical representations for processing within-talker variability in ETV, depending on the time course of spoken word recognition.     

Repetition priming in an auditory lexical decision task: Effects of lexical status

The effect of lexical status on the time course of repetition priming was examined in an auditory lexical decision task. Words and nonwords were repeated at lags of 0, 1, 4, and 8 items (Experiment 1A) and 0, 2, 4, and 8 items (Experiment 1B). The pattern of repetition effects differed for words and nonwords in that repetition priming for nonwords at lag 0 was significantly greater than for words. The magnitude of this effect decreased when one or more items intervened. A second experiment, replicating Experiment 1A with visual presentation, clarified that the greater magnitude of repetition priming for nonwords at lag 0 is unique to the auditory modality. This finding suggests that in the course of forming a stable perceptual representation, the details of the acoustic/phonological information of an auditory stimulus are more readily available for nonwords than for words. The capacity to carry this phonological information is limited, however, and can only be maintained until another stimulus is encountered.     

Examining the time course of indexical specificity effects in spoken word recognition

Variability in talker identity and speaking rate, commonly referred to as indexical variation, has demonstrable effects on the speed and accuracy of spoken word recognition. The present study examines the time course of indexical specificity effects to evaluate the hypothesis that such effects occur relatively late in the perceptual processing of spoken words. In 3 long-term repetition priming experiments, the authors examined reaction times to targets that were primed by stimuli that matched or mismatched on the indexical variable of interest (either talker identity or speaking rate). Each experiment was designed to manipulate the speed with which participants processed the stimuli. The results demonstrate that indexical variability affects participants' perception of spoken words only when processing is relatively slow and effortful.     

Negative priming and perceptual fluency: More than what meets the eye

In two priming experiments, we manipulated the perceptual quality of the target or the distractor on the prime trial; the stimuli were repeated or novel. Negative priming was found to be contingent on stimulus repetition, because it was obtained with repeated items but not with novel items. Prime trial perceptual degradation modulated negative priming for repeated items but had no effect on priming in ignored repetition conditions using novel stimuli. These patterns were obtained even when the effect of perceptual degradation was (1) greater than the effect of stimulus repetition and (2) greater for novel words than for repeated words. Although stimulus repetition increases perceptual fluency, the activation of perceptual representations by itself is not sufficient to produce negative priming. Instead, we suggest that negative priming is a manifestation of an activation-sensitive inhibitory mechanism that functions to reduce response competition.     

The word frequency effect in recognition memory versus repetition priming

The role of word frequency in recognition memory and repetition priming was investigated by using a manipulation of attention. In Experiment 1, the lexical decision task produced greater repetition priming for low-frequency words than for high-frequency words following either the attended or the unattended study condition. The recognition memory test, on the other hand, showed a low-frequency word advantage only following the attended study condition. Furthermore, this advantage was limited to the measure of recognition memory based on conscious recollection of the study episode. In Experiment 2, a speeded recognition memory test replicated the pattern obtained with the unspeeded recognition memory test in Experiment 1. These results argue against the view that the word frequency effects in recognition memory and repetition priming have the same origin. Instead, the results suggest that the word frequency effect in recognition memory has its locus in conscious recollection.     

Negative priming and perceptual fluency: more than what meets the eye

In two priming experiments, we manipulated the perceptual quality of the target or the distractor on the prime trial; the stimuli were repeated or novel. Negative priming was found to be contingent on stimulus repetition, because it was obtained with repeated items but not with novel items. Prime trial perceptual degradation modulated negative priming for repeated items but had no effect on priming in ignored repetition conditions using novel stimuli. These patterns were obtained even when the effect of perceptual degradation was (1) greater than the effect of stimulus repetition and (2) greater for novel words than for repeated words. Although stimulus repetition increases perceptual fluency, the activation of perceptual representations by itself is not sufficient to produce negative priming. Instead, we suggest that negative priming is a manifestation of an activation-sensitive inhibitory mechanism that functions to reduce response competition.     

Repetition priming and face processing: Priming occurs within the system that responds to the identity of a face

A familiar stimulus that has recently been recognized will be recognized a second time more quickly and more accurately than if it had not been primed by the earlier encounter. This is the phenomenon of “repetition priming”. Four experiments on repetition priming of face recognition suggest that repetition priming is a consequence of changes within the system that responds to the familiarity of a stimulus. In Experiment 1, classifying familiar faces by occupation facilitated subsequent responses to the same faces in a familiarity decision task (Is this face familiar or unfamiliar?) but not in an expression decision task (Is this face smiling or unsmiling?) or a sex decision task (Is this face male or female?). In Experiment 2, familiar faces showed repetition priming in a familiarity decision task, regardless of whether a familiarity judgment or an expression judgment had been required when the faces were first encountered. Expression decisions to familiar faces again failed to show repetition priming. In Experiment 3, familiar faces showed repetition priming in a familiarity decision task, regardless of whether a familiarity judgment or a sex judgment had been asked for when the faces were first encountered. Sex decisions to familiar faces again failed to show repetition priming. In Experiment 4, familiarity decisions continued to show repetition priming when a brief presentation time with encouragement to respond while the face was displayed reduced response latencies to speeds comparable to those for sex and expression judgments in Experiments 1 to 3. The results are problematic for theories that propose that repetition priming is mediated by episodic records of previous acts of stimulus encoding.     

When is all understood and done? The psychological reality of the recognition point

Using lexical decision, the effects of primes of different length on spoken word recognition were evaluated in three partial repetition priming experiments. Prime length was determined via gating (Experiments 1a and 2a). It was shorter than, equivalent to, or longer than the recognition point (RP), or a complete word. In Experiments 1b and 1c, priming increased with prime length and was independent of reaction time. The influence of sensory information following the RP was investigated in Experiment 2b. Latencies decreased with increasing prime length, but priming decreased only for complete words. RP and complete words have a special status. Lexical representations are activated to different degrees at the RP and at word offset.     

Abstractionist versus episodic theories of repetition priming and word identification

This paper reviews research relevant to the question of whether words are identified through the use of abstract lexical representations, specific episodic representations, or both. Several lines of evidence indicate that specific episodes participate in word identification. First, pure abstractionist theories can explain short-term but not long-term repetition priming. Second, long-term repetition priming is sensitive to changes in surface features or episodic context between presentations of a word. Finally, long-term priming for pseudowords is also difficult for pure abstractionist theories to explain. Alternative approaches to word identification are discussed, including both pure episodic theories and theories in which both episodes and abstract representations play a role.