Nonword Processing Research Articles

A PET investigation of lexicality and phonotactic frequency in oral language processing

Lexicality and phonotactic frequency effects are observed in many cognitive studies on language processing, but little is known about their underlying neural substrates, especially with regard to phonotactic frequency effects. Here, we conducted a positron emission tomography (PET) study in which 11 right-handed volunteers had either to repeat or to listen to lists of words, high phonotactic frequency nonwords, and low phonotactic frequency nonwords. The comparison of word versus nonword processing consistently confirmed previous findings of left temporal and prefrontal activations classically ascribed to lexicosemantic processing. Higher activation was found in the right posterior superior temporal gyrus when comparing high phonotactic frequency nonwords to words, but not when comparing low phonotactic frequency nonwords to words. We propose that this region is implicated in the formation of temporary phonological representations for high-probability phonological events, which may support processing of high phonotactic frequency nonwords.

Divided attention and prerecognition processing of spoken words and nonwords.

Three recognition memory experiments examined phonemic similarity and false recognition under conditions of divided attention. The manipulation was presumed to have little effect on automatic, perceptual influences of memory. Prior research demonstrated that false recognition of a test word (e.g., discrepancy) was higher if the study list included a nonword derived from the future test word by changing a phoneme near the end of the item (e.g., discrepan/l/y) relative to an early phoneme change (e.g., /l/iscrepancy). The difference has been attributed to automatic, implicit activation of test words during prerecognition processing of related nonwords. Three experiments demonstrated that the late-change condition also contributed to higher false recognition rates with divided attention at encoding. Dividing attention disrupted recognition memory of studied words in Experiments 1 and 3. Results are discussed in terms of their relevance for an interpretation emphasizing the automatic, implicit activation of candidate words that occurs in the course of identifying spoken words and nonwords.

Neuromagnetic spectral distribution of implicit processing of words.

Neuromagnetic spectral distributions when silently viewing words and non-words were investigated using a 151-channel whole head MEG system. The data were analyzed with synthetic aperture magnetometry (SAM). The dominant changes of spectral power were identified in the parietal and occipital cortices in 15-30 Hz, 30-60 Hz and 60-125 Hz bands following both word and non-word stimulations. The changes in Broca's and Wernicke's areas were consistently observed in 60-125 Hz bands, mainly following word stimulation. The results indicated that the occipital and parietal cortices were most probably involved in visuospatial processing of words and non-words. The language areas, particularly Broca's and Wernickes's areas, might be involved in implicit word processing such as verbal searching and/or internal speech.

Characteristics of dyslexia in a Dutch family.

This study investigates the characteristics of 19 members of a Dutch family. Nine of them, recognized as dyslexic in their early years, are compared with six non-dyslexic members, whereas four form a non-classified category. From their personal histories, it is clear that the dyslexics had a long and troublesome educational career, while the non-dyslexics did not. However, probably because the dyslexic members had considerable intellectual resources and talents in mathematics and technical skills, most succeeded in getting degrees of a reasonably high standard and jobs that more or less matched their talents. In cognitive terms, differences in non-word processing, independent of response mode (reading, spelling, oral repetition), and in speeded word reading suggest stable deficits in phonological processing and in task-specific automatization. The spelling of words was fairly accurate, possibly because compensatory strategies were used, also indicated by remarks of the dyslexic members. Outside the reading and spelling area, only small and non-significant differences appeared in tasks tapping verbal short-term memory, rapid naming and working memory. However, the predicted discrepancy between the conceptual and the sequential factor of the Wechsler intelligence test was shown by most dyslexics. Two of the four non-classified members of the family, who could not be classified as dyslexic because no early diagnosis was made, but had experienced learning problems at school, showed more or less the same characteristics, but were less successful at school and in society. In the discussion, the use of a family control group in studies with a large age range is recommended.

Right posterior superior temporal gyrus is activated for the processing of high and low phonotactic frequency nonwords compared to words

Right posterior superior temporal gyrus is activated for the processing of high and low phonotactic frequency nonwords compared to words

Perception of Wordlikeness: Effects of Segment Probability and Length on the Processing of Nonwords

A probabilistic phonotactic grammar based on the probabilities of the constituents contained in a dictionary of English was used to generate multisyllabic nonwords. English-speaking listeners evaluated the wordlikeness of these patterns. Wordlikeness ratings were higher for nonwords containing high-probability constituents and were also higher for nonwords with fewer syllables. Differences in the processing of these same nonwords that partially reflected their perceived wordlikeness were also found in a recognition memory task. Nonwords with higher probability constituents yielded better recognition memory performance, suggesting that participants were able to use their knowledge of frequently occurring lexical patterns to improve recognition. These results suggest that lexical patterns provide the foundation of an emergent phonological competence used to process nonwords in both linguistic and metalinguistic tasks.

Patterns of Word and Nonword Processing in Skilled and Less-Skilled Readers.

Sixty-eight third graders who were less-skilled readers performed more poorly than younger reading-level control children on tests of pseudoword reading and phonological sensitivity. These findings add to the growing consensus that the proximal cause of reading difficulties are spelling-sound coding problems that result from deficient underlying phonological processes and structures. Analyses of their word and pseudoword reading performance provided some suggestive evidence that less-skilled readers are less sensitive than their younger reading-level matched counterparts to all subword-size orthographic units, perhaps especially to grapheme-sized units.

Event-related potentials to stimuli with emotional impact in posttraumatic stress patients

Background: Psychophysiological research has given conflicting results with respect to whether the abnormal physiologic responses observed in posttraumatic stress disorder (PTSD) reflect a general abnormality or are linked to trauma-related stimuli. We studied differences in the central nervous processing of words with emotional impact in survivors after a ship fire disaster. Methods: Event-related potentials were studied in 11 survivors with posttraumatic stress pathology, and compared with 9 survivors without such pathology. Nonwords and words with negative or positive emotional valence were used as distractors in a P3 oddball paradigm. Results: PTSD subjects had increased N1 latency to standard tones and increased positive amplitude to both words and nonwords compared with controls, occurring between 200 and 350 msec after stimulus onset. The amplitudes to emotionally meaningful words were significantly related to Clinician-Administered PTSD Scale-assessed PTSD dimensions, in particular avoidance and arousal. Conclusions: The abnormality in information processing observed in PTSD patients seems in part to be linked with increased attention, in part with emotional responses to the trauma. Intrusion was mainly related to the processing of nonwords, while arousal and avoidance were related to event-related potential amplitudes to emotionally meaningful words, suggesting that intrusion has a different neurobiological basis than arousal and avoidance.

Word, Pseudoword, and Nonword Processing: A Multitask Comparison Using Event-Related Brain Potentials

Event-related brain potentials (ERPs) to words, pseudowords, and nonwords were recorded in three different tasks. A letter search task was used in Experiment 1. Performance was affected by whether the target letter occurred in a word, a pseudoword, or a random nonword. ERP results corroborated the behavioral results, showing small but reliable ERP differences between the three stimulus types. Words and pseudowords differed from nonwords at posterior sites, whereas words differed from pseudowords and nonwords at anterior sites. Since deciding whether the target letter was present or absent co-occurred with stimulus processing in Experiment 1, a delayed letter search task was used in Experiment 2. ERPs to words and pseudowords were similar and differed from ERPs to nonwords, suggesting a primary role of orthographic and phonological processing in the delayed letter search task. To increase semantic processing, a categorization task was used in Experiment 3. Early differences between ERPs to words and pseudowords at left posterior and anterior locations suggested a rapid activation of lexico-semantic information. These findings suggest that the use of ERPs in a multiple task design makes it possible to track the time course and the activation of multiple sources of linguistic information when processing words, pseudowords, and nonwords. The task-dependent nature of the effects suggests that the language system can use multiple sources of linguistic information in flexible and adaptive ways.

Event-related potentials differentiate the effects of aging on word and nonword repetition in explicit and implicit memory tasks.

Explicit memory declines with age while implicit memory remains largely intact. These experiments extended behavioral findings by recording event-related potentials (ERPs) in young and elderly adults during repetition priming and recognition memory paradigms. Words and pronounceable nonwords repeated after 1 of 3 delays. Stimuli were categorized as either word-nonword or old-new. Repeated items elicited more positive-going potentials in both tasks. Hemispheric asymmetries for word and nonword processing were observed during lexical decision: Repetition effects were larger over the left hemisphere for words and over the right hemisphere for nonwords. For the young, ERP repetition effects were larger during recognition memory. For old adults, conversely, repetition produced more positive-going waveforms during lexical decision. The elderly had ERP and behavioral deficits at long recognition delays. ERP repetition effects in the elderly, like behavioral performance, were preserved in an implicit task but impaired in an explicit memory task.

Hemispheric Independence in Word Recognition: Evidence from Unilateral and Bilateral Presentations

We compared behavioral laterality effect in a lexical decision task using cued unilateral or bilateral presentations of different stimuli to normal subjects. The goals were to determine the effects of lexical variables on word recognition in each hemisphere under conditions of maximal independence of information processing in the two hemispheres and to assess the degree of residual interhemispheric effects that can still exist then. Bilateral presentations increased hemispheric independence in word recognition, indexed by a significant interaction of response hand with target visual field. Bilateral presentations also selectively impaired word decisions, suggesting that word processing benefits from interhemispheric interaction, whereas nonword processing is done independently in each hemisphere. Indeed, there was a significant congruity effect for word targets only, whereby the wordness of the unattended stimulus affected the speed of processing of attended word targets. Word frequency and regularity affected both hemispheres equally, arguing against the hemispheric interpretation of the dual route model of word recognition. Length affected the processing of nonwords more than words and in the left visual field more than in the right visual field. Taken together, the data support the conclusion that each normal hemisphere can control word recognition independently of the other.

Phonological processing of nonwords in deep dyslexia: Typical and independent?

Patients with acquired deep dyslexia are unable to read nonwords aloud. The deficit has therefore been attributed to damage in nonlexical phonological processing. Buchanan, Hildebrandt and MacKinnon [5 Journal of Neurolingistics 8, 163–182, 1994] demonstrated that a deep dyslexic patient could process nonword phonology in two implicit tests. The generality of this claim is examined by replicating the Buchanan et al. experiments with two other deep dyslexic patients. Dissociations between lexical and nonlexical processing are examined by manipulating nonword phonology in a task that does not require lexical analysis. The results suggest that sensitivity to nonword phonology in deep dyslexia is common and is distinct from a purely lexical analysis.

Phonological processing of nonwords by a deep dyslexic patient: A rowse is implicitly a rose

Recent work has shown that implicit phonological knowledge plays a role in the word recognition performance of deep dyslexics [H ildebrandt, N. and S okol, S.M. Reading and Writing, 5, 43–68, 1993; K atz, R.B. and L anzoni, S.M. Quarterly Journal of Experimental Psychology 45, 575–608, 1992]. The results of the current study extend this examination to include the investigation of implicit knowledge of nonword phonology. The data from two lexical decision tasks indicate that nonword phonology is available for processing by a deep dyslexic patient in that she produced a significant pseudohomophone effect as well as semantic priming with pseudohomophone primes in lexical decision.

Processing of Kanji and Kana characters within Japanese words

Two experiments were conducted to examine the temporal relationship between whole-word and character processing in Japanese. Two kinds of Japanese script were used as stimuli: Kanji, an ideographic script, and Kana, a syllabic script. In Experiment 1, Kanji word processing and Kanji character processing were examined using a successive visual comparison task. The whole-word advantage (Marmurek, 1986) was not found. In Experiment 2, Kana words and characters were used. As in Experiment 1, no whole-word advantage was found. The absence of the whole-word advantage is attributed to the fact that Kanji and Kana characters represent higher level units of processing than alphabetic letters. The difference between word and nonword processing was shown by manipulations of the visual similarity and the homophony between stimuli presented successively. Visual similarity affected both words and nonwords, whereas homophony affected words only.

Are there independent lexical and nonlexical routes in word processing? An evaluation of the dual-route theory of reading

AbstractOne of the most popular and influential theories of word processing, dual-route theory, proposes that there are two functionally independent means of processing words, one involving access to lexical knowledge and the other involving nonlexical grapheme-to-phoneme conversion. Three topics germane to this theory are the processing of nonwords, spelling regularity effects, and the manner in which reading may be impaired following selective damage to either route. This paper evaluates evidence on these topics, and in each case the claims of the theory for an independent nonlexical processing route are called into question. This conclusion is further supported by a discussion of the linguistic constraints that limit any nonlexical grapheme—phoneme conversion process. Some alternative approaches to visual word processing, which share the assumption that lexical knowledge can guide the assembly of phonological information, are discussed. It is argued that these approaches should direct future research.

Event-related potentials and the phonological processing of words and non-words

Event-related potentials (ERPs) were recorded during a task which required subjects to discriminate between rhyming and non-rhyming visually presented pairs of letter strings, consisting of equal proportions of word-word and word-non-word combinations. Pair members were presented sequentially with an interstimulus interval of 1.56 sec. As in a previous study [R UGG, M. D., Brain Lang. In press], ERPs elicited by rhyming and non-rhyming words were differentiated by a late negative component (N450) in waveforms following the non-rhyming words. This effect was greatest over the midline and the right hemisphere. The same rhyme/non-rhyme difference was also observed, to an extent, in ERPs elicited by non-words. It is concluded that N450, presumed to be related to the “N400” component observed under conditions of semantic incongruity [ Kutas, M. and Hillyard, S.A., Science 207, 203–205, 1980] does not seem to depend on linguistic processing at the semantic level for its modulation.

Word unitization examined using an interference paradigm

A “same”-“different” interference paradigm was utilized to investigate the differential nature of word nonword processing. Eight subjects viewed tachistoscopically presented pairs of letters and made speeded comparison judgments on the basis of name identity. When present, noise trigrams composing words or anagrams were positioned directly between the target letters. The results supported a word unitization hypothesis of word recognition. Anagrams increased RTs for “same” responses more than their counterpart words when used as noise items. The data are interpreted in terms of selective attention, response competition, and models of word recognition.