The effects of talker familiarity on spoken word identification in younger and older listeners

The present study was designed to examine age differences in the ability to use voice information acquired intentionally (Experiment 1) or incidentally (Experiment 2) as an aid to spoken word identification. Following both implicit and explicit voice learning, participants were asked to identify novel words spoken either by familiar talkers (ones they had been exposed to in the training phase) or by 4 unfamiliar voices. In both experiments, explicit memory for talkers' voices was significantly lower in older than in young listeners. Despite this age-related decline in voice recognition, however, older adults exhibited equivalent, and in some cases greater, benefit than young listeners from having words spoken by familiar talkers. Implications of the findings for age-related changes in explicit versus implicit memory systems are discussed.     

The growth of lexical constraints on spoken word recognition

In this study, we examined the influence of various sources of constraint on spoken word recognition in a mispronunciation-detection task. Five- and 8-year-olds and adults were presented with words (intact or with word-initial or noninitial errors) from three different age-of-acquisition categories. "Intact" and "mispronounced" responses were collected for isolated words with or without a picture referent (Experiment 1) and for words in constraining or unconstraining sentences (Experiment 2). Some evidence for differential attention to word-initial as opposed to noninitial acoustic-phonetic information (and thus the influence of sequential lexical constraints on recognition) was apparent in young children's and adults' response criteria and in older children's and adults' reaction times. A more marked finding, however, was the variation in subjects' performance, according to several measures, with age and lexical familiarity (defined according to adults' subjective age-of-acquisition estimates). Children's strategies for responding to familiar and unfamiliar words in different contexts are discussed.     

Knowing what a novel word is not: Two-year-olds 'listen through' ambiguous adjectives in fluent speech

Three studies investigated how 24-month-olds and adults resolve temporary ambiguity in fluent speech when encountering prenominal adjectives potentially interpretable as nouns. Children were tested in a looking-while-listening procedure to monitor the time course of speech processing. In Experiment 1, the familiar and unfamiliar adjectives preceding familiar target nouns were accented or deaccented. Target word recognition was disrupted only when lexically ambiguous adjectives were accented like nouns. Experiment 2 measured the extent of interference experienced by children when interpreting prenominal words as nouns. In Experiment 3, adults used prosodic cues to identify the form class of adjective/noun homophones in string-identical sentences before the ambiguous words were fully spoken. Results show that children and adults use prosody in conjunction with lexical and distributional cues to ‘listen through’ prenominal adjectives, avoiding costly misinterpretation.     

Aging and the Deletion Function of Inhibition

The present study was adapted from the sentence completion task of Hartman and Hasher (1991). We addressed the question raised by Burke (1997): are the age-related differences in priming effects found in that task better explained by deficits in explicit memory or by inefficient inhibitory mechanisms? In the study phase, older and younger adults read high cloze sentences ending with an expected or an unexpected final word. In the second phase, participants were asked to complete sentence frames with either the final word presented during the study phase (inclusion condition) or with another, new word (exclusion condition). The third phase was an indirect memory test of perceptual identification. Finally, we compared explicit memory for recalled and inhibited words in a recognition test. In perceptual identification by older adults, priming was equivalent for recalled and inhibited words, whereas in younger adults priming was higher for recalled than for inhibited words. In the explicit memory test, recognition scores were lower for inhibited words in both age groups. These results are consistent with the view of Hasher and Zacks (1988), who assume an age-related decline in the ability to suppress no-longer-relevant information     

Working memory capacity for spoken sentences decreases with adult ageing: recall of fewer but not smaller chunks in older adults

Previous studies show that older adults have poorer immediate recall for language but the reason is unknown. Older adults may recall fewer chunks from working memory, or may have difficulty binding words together to form multi-unit chunks. We examined these two hypotheses by presenting four types of spoken sentences for immediate free recall, differing in the number and length of chunks per trial: four short, simple sentences; eight such sentences; four compound sentences, each incorporating two meaningful, short sentences; and four random word lists, each under a sentence-like intonation. Older adults recalled words from (accessed) fewer clauses than young adults, but there was no ageing deficit in the degree of completion of clauses that were accessed. An age-related decline in working memory capacity measured in chunks appears to account for deficits in memory for spoken language.     

Similarity neighborhoods of spoken two-syllable words: retroactive effects on multiple activation

This research examines the recognition of two-syllable spoken words and the means by which the auditory word recognition process deals with ambiguous stimulus information. The experiments reported here investigate the influence of individual syllables within two-syllable words on the recognition of each other. Specifically, perceptual identification of two-syllable words comprised of two monosyllabic words (spondees) was examined. Individual syllables within a spondee were characterized as either "easy" or "hard" depending on the syllable's neighborhood characteristics; an easy syllable was defined as a high-frequency word in a sparse neighborhood of low-frequency words, and a hard syllable as a low-frequency word in a high-density, high-frequency neighborhood. In Experiment 1, stimuli were created by splicing together recordings of the component syllables of the spondee, thus equating for syllable stress. Additional experiments tested the perceptual identification of naturally produced spondees, spliced nonwords, and monosyllables alone. Neighborhood structure had a strong effect on identification in all experiments. In addition, identification performance for spondees with a hard-easy syllable pattern was higher than for spondees with an easy-hard syllable pattern, indicating a primarily retroactive pattern of influence in spoken word recognition. Results strongly suggest that word recognition involves multiple activation and delayed commitment, thus ensuring accurate and efficient recognition.     

Older adults can inhibit high-probability competitors in speech recognition

Younger and older adults identified a series of target words spoken in sentence contexts from their onsets only (i.e., word-onset gating). Sentences were drawn from published norms so that the contextual probabilities of the final words were known. the target words were always the second most probable responses to the sentence contexts, and the probabilities of the target words and the most likely alternatives were systematically varied. Results showed that older adults required more word-onset information for correct recognition, and their responses were more affected by the probability of the occurrence of the target word, supporting previous suggestions that older listeners differentially rely on contextual support in spoken word recognition. Contrary to the Inhibition Hypothesis, however, that older adults have especial difficulty suppressing irrelevant information once it is activited, elders' ability to recognize the target was not particularly disrupted by the presence of a high-probability competitor.     

The influence of the lexicon on speech read word recognition: contrasting segmental and lexical distinctiveness

The neighborhood activation model (NAM; P. A. Luce & Pisoni, 1998) of spoken word recognition was applied to the problem of predicting accuracy of visual spoken word identification. One hundred fifty-three spoken consonant-vowel-consonant words were identified by a group of 12 college-educated adults with normal hearing and a group of 12 college-educated deaf adults. In both groups, item identification accuracy was correlated with the computed NAM output values. Analysis of subsets of the stimulus set demonstrated that when stimulus intelligibility was controlled, words with fewer neighbors were easier to identify than words with many neighbors. However, when neighborhood density was controlled, variation in segmental intelligibility was minimally related to identification accuracy. The present study provides evidence of a common spoken word recognition system for both auditory and visual speech that retains sensitivity to the phonetic properties of the input.     

Learning to ignore distracters

Eye tracking has indicated that older and young adults process distracters similarly when reading single sentences. The present study extended this approach by presenting short paragraphs, sentence by sentence. Eye tracking measures included reading times per word, and the duration of the first fixation and total fixations to the distracters and target words. Comprehension was tested following each paragraph, and recognition of distracters and target words was assessed. The results indicated that young adults were able to learn to ignore the distracters as they read through the paragraphs, whereas older adults were less successful at learning to ignore the distracters.     

The effect of lexical frequency on spoken word recognition in young and older listeners

When identifying spoken words, older listeners may have difficulty resolving lexical competition or may place a greater weight on factors like lexical frequency. To obtain information about age differences in the time course of spoken word recognition, young and older adults' eye movements were monitored as they followed spoken instructions to click on objects displayed on a computer screen. Older listeners were more likely than younger listeners to fixate high-frequency displayed phonological competitors. However, degradation of auditory quality in younger listeners does not reproduce this result. These data are most consistent with an increased role for lexical frequency with age.     

Frequent false hearing by older adults: the role of age differences in metacognition

In two experiments testing age differences in the subjective experience of listening, which we call meta-audition, young and older adults were first trained to learn pairs of semantic associates. Following training, both groups were tested on identification of words presented in noise, with the critical manipulation being whether the target item was congruent, incongruent, or neutral with respect to prior training. Results of both experiments revealed that older adults compared to young adults were more prone to "false hearing," defined as mistaken high confidence in the accuracy of perception when a spoken word had been misperceived. These results were obtained even when performance was equated across age groups on control items by reducing the noise level for older adults. Such false hearing is shown to reflect older adults' heavier reliance on context. Findings suggest that older adults' greater ability to benefit from semantic context reflects their bias to respond consistently with the context, rather than their greater skill in using context. Procedures employed are unique in measuring the subjective experience of hearing as well as its accuracy. Both theoretical and applied implications of the findings are discussed. Convergence of results with those showing higher false memory, and false seeing are interpreted as showing that older adults are less able to constrain their processing in ways that are optimal for performance of a current task. That lessened constraint may be associated with decline in frontal-lobe functioning.     

Auditory-phonetic projection and lexical structure in the recognition of sine-wave words

Speech remains intelligible despite the elimination of canonical acoustic correlates of phonemes from the spectrum. A portion of this perceptual flexibility can be attributed to modulation sensitivity in the auditory-to-phonetic projection, although signal-independent properties of lexical neighborhoods also affect intelligibility in utterances composed of words. Three tests were conducted to estimate the effects of exposure to natural and sine-wave samples of speech in this kind of perceptual versatility. First, sine-wave versions of the easy and hard word sets were created, modeled on the speech samples of a single talker. The performance difference in recognition of easy and hard words was used to index the perceptual reliance on signal-independent properties of lexical contrasts. Second, several kinds of exposure produced familiarity with an aspect of sine-wave speech: (a) sine-wave sentences modeled on the same talker; (b) sine-wave sentences modeled on a different talker, to create familiarity with a sine-wave carrier; and (c) natural sentences spoken by the same talker, to create familiarity with the idiolect expressed in the sine-wave words. Recognition performance with both easy and hard sine-wave words improved after exposure only to sine-wave sentences modeled on the same talker. Third, a control test showed that signal-independent uncertainty is a plausible cause of differences in recognition of easy and hard sine-wave words. The conditions of beneficial exposure reveal the specificity of attention underlying versatility in speech perception.     

Word frequency influences on the list length effect and associative memory in young and older adults

Many studies show that age deficits in memory are smaller for information supported by pre-experimental experience. Many studies also find dissociations in memory tasks between words that occur with high and low frequencies in language, but the literature is mixed regarding the extent of word frequency effects in normal ageing. We examined whether age deficits in episodic memory could be influenced by manipulations of word frequency. In Experiment 1, young and older adults studied short and long lists of high- and low-frequency words for free recall. The list length effect (the drop in proportion recalled for longer lists) was larger in young compared to older adults and for high- compared to low-frequency words. In Experiment 2, young and older adults completed item and associative recognition memory tests with high- and low-frequency words. Age deficits were greater for associative memory than for item memory, demonstrating an age-related associative deficit. High-frequency words led to better associative memory performance whilst low-frequency words resulted in better item memory performance. In neither experiment was there any evidence for age deficits to be smaller for high- relative to low-frequency words, suggesting that word frequency effects on memory operate independently from effects due to cognitive ageing.     

Aging and the use of interword spaces during reading: Evidence from eye movements

In an eye movement experiment, we assessed the performance of young (18–30 years) and older (65 + years) adult readers when sentences contained conventional interword spaces, when interword spaces were removed, or when interword spaces were replaced by nonlinguistic symbols. The replacement symbol was either a closed square (■) that provided a salient (low-spatial-frequency) cue to word boundaries, or an open square (□) that provided a less salient cue and included features (vertical and horizontal lines) similar to those found in letters. Removing or replacing interword spaces slowed reading times and impaired normal eye movement behavior for both age groups. However, this disruption was greater for the older readers, particularly when the replacement symbol did not provide a salient cue as to word boundaries. Specific influences of this manipulation on word identification during reading were assessed by examining eye movements for a high- or low-frequency target word in each sentence. Standard word frequency effects were obtained for both age groups when text was spaced normally, and although the word frequency effect was larger when spaces were removed or filled, the increases were similar across age groups. Therefore, whereas older adults’ normal eye movements were substantially disrupted when text lacked conventional interword spaces, the process of lexical access associated with the word frequency effect was no more difficult for older than for young adults. The indication, therefore, is that although older adults struggle from the loss of conventional cues to word boundaries, this is not due to additional difficulties in word recognition.     

Phonological ambiguity and lexical ambiguity: effects on visual and auditory word recognition

Three experiments in Serbo-Croatian were conducted on the effects of phonological ambiguity and lexical ambiguity on printed word recognition. Subjects decided rapidly if a printed and a spoken word matched or not. Printed words were either phonologically ambiguous (two possible pronunciations) or unambiguous. If phonologically ambiguous, either both pronunciations were real words or only one was, the other being a nonword. Spoken words were necessarily unambiguous. Half the spoken words were auditorily degraded. In addition, the relative onsets of speech and print were varied. Speed of matching print to speech was slowed by phonological ambiguity, and the effect was amplified when the stimulus was also lexically ambiguous. Auditory degradation did not interact with print ambiguity, suggesting that perception of the spoken word was independent of the printed word.     

The role of vocabulary ability during visual word recognition in younger and older adults

The role that vocabulary ability plays in adult age differences in word recognition was investigated. In Experiment 1, 44 older adults (ages 61-93 years) were compared with 44 younger adults (ages 18-39 years) on a standard lexical-decision task, with ambiguous words, unambiguous words, and pseudowords serving as stimuli. In Experiment 1, the Wechsler Adult Intelligence Scale-Revised (WAIS-R; D. Wechsler, 1981) vocabulary performance was uncontrolled across the younger and older adults, and the older adults had higher WAIS-R scores. There was no Group x Stimulus interaction. In Experiment 2, the data from the same 44 older adults were compared with data from a new sample of 44 younger adults (ages 18-44). Both groups were then matched on WAIS-R performance. Results revealed a significant Group x Stimulus interaction. Reaction time differences between the younger and older groups on the ambiguous words and unambiguous words were identical. The differences in reaction times for words and pseudowords were greater in the older adults. The importance of vocabulary ability during word recognition and lexical processing is discussed.     

The oral and written side of word production in young and older adults: generation of lexical neighbors

The aim of the present study was to investigate the effects of aging on both spoken and written word production by using analogous tasks. To do so, a phonological neighbor generation task (Experiment 1) and an orthographic neighbor generation task (Experiment 2) were designed. In both tasks, young and older participants were given a word and had to generate as many words as they could think of by changing one phoneme in the target word (Experiment 1) or one letter in the target word (Experiment 2). The data of the two experiments were consistent, showing that the older adults generated fewer lexical neighbors and made more errors than the young adults. For both groups, the number of words produced, as well as their lexical frequency, decreased as a function of time. These data strongly support the assumption of a symmetrical age-related decline in the transmission of activation within the phonological and orthographic systems.     

Greater priming for previously distracting information in young than older adults when suppression is ruled out

The use of previously distracting information on memory tests with indirect instructions is usually age-equivalent, while young adults typically show greater explicit memory for such information. This could reflect qualitatively distinct initial processing (encoding) of distracting information by younger and older adults, but could also be caused by greater suppression of such information by younger adults on tasks with indirect instructions. In Experiment 1, young and older adults read stories containing distracting words, which they ignored, before studying a list of words containing previously distracting items for a free recall task. Half the participants were informed of the presence of previously distracting items in the study list prior to recall (direct instruction), and half were not (indirect instruction). Recall of previously distracting words was age-equivalent in the indirect condition, but young adults recalled more distracting words in the direct condition. In Experiment 2, participants performed the continuous identification with recognition task, which captures a measure of perceptual priming and recognition on each trial, and is immune to suppression. Priming and recognition of previously distracting words was greater in younger than older adults, suggesting that the young engage in more successful suppression of previously distracting information on tasks in which its relevance is not overtly signaled.     

语言能力的老化机制：语言特异性与非特异性因素的共同作用

语言能力的衰退是由于一般认知能力衰退引起的, 还是由于语言加工系统的衰退引起的, 抑或是两者的共同作用?研究中测量了青年组和老年组的一般认知能力(加工速度、工作记忆和抑制能力), 以及在词汇、句子和语篇三个水平上的语言理解能力和语言产生能力。结果发现, 一般认知能力、语言理解和语言产生能力都存在年老化现象。分层回归分析表明, 一般认知能力对语言能力的贡献, 以及语言理解能力和产生能力之间的相互贡献在青年组和老年组中是不同的, 且存在词汇、句子和语篇水平上的差异。在词汇水平上, 青年人的成绩能够被一般认知能力和另一种语言能力所显著预测, 而老年人的成绩却不受一般认知因素影响; 在句子水平上, 青年人的成绩仍能被一般认知能力或另一种语言能力所解释, 但这两类变量都无法预测老年人的任务成绩; 在语篇水平上, 青年人理解任务的成绩显著地受到产生能力影响, 而老年人的理解和产生任务成绩则分别可以被一般认知能力和语言理解能力所解释。对组间差异的回归分析表明, 一般认知能力和另一种语言能力对组间差异都有显著贡献, 且前者的贡献大于后者。上述研究结果表明, 语言能力的老化是语言特异性因素和非特异性因素共同作用的结果。     

Case-mixing effects on children's word recognition: Lexical feedback and development

Presenting words in MiXeD cAsE has previously been shown to disrupt naming performance of adult readers. This effect is greater on nonwords than it is on real words. There have been two main accounts of this interaction. First, case mixing may disrupt naming via non-lexical spellingto-sound correspondences to a greater extent than it disrupts lexical naming. Alternatively, stored lexical knowledge of words may feed back to a visual analysis level during processing of a visually presented word, helping known words to overcome the visual disruption caused by case mixing. In the present study, when young children (aged 6 and 8 years) were tested, case mixing did not disrupt nonword naming more than word naming. However, slightly older children (aged 9 years) demonstrated the same pattern of performance as adults. These results support the view that topdown lexical information can aid overcoming visual disruption to words, and that beginning readers have not developed the stored word knowledge necessary to allow this. In addition, a greater case-mixing effect on high-frequency words for the youngest age group (6-year-olds) suggests that their word recognition may be based more on wholistic visual features than is that of older children.