Phonological and conceptual activation in speech comprehension

We propose that speech comprehension involves the activation of token representations of the phonological forms of current lexical hypotheses, separately from the ongoing construction of a conceptual interpretation of the current utterance. In a series of cross-modal priming experiments, facilitation of lexical decision responses to visual target words (e.g., time) was found for targets that were semantic associates of auditory prime words (e.g., date) when the primes were isolated words, but not when the same primes appeared in sentence contexts. Identity priming (e.g., faster lexical decisions to visual date after spoken date than after an unrelated prime) appeared, however, both with isolated primes and with primes in prosodically neutral sentences. Associative priming in sentence contexts only emerged when sentence prosody involved contrastive accents, or when sentences were terminated immediately after the prime. Associative priming is therefore not an automatic consequence of speech processing. In no experiment was there associative priming from embedded words (e.g., sedate-time), but there was inhibitory identity priming (e.g., sedate-date) from embedded primes in sentence contexts. Speech comprehension therefore appears to involve separate distinct activation both of token phonological word representations and of conceptual word representations. Furthermore, both of these types of representation are distinct from the long-term memory representations of word form and meaning.     

Phonological activation in anaphoric lexical access (ALA).

Simner and Smyth (1998) propose that anaphoric lexical access (ALA) occurs at an anaphor and targets the lexical entry (specifically, the lemma) of the antecedent. Since the word frequency effect (e.g., Rubenstein et al., 1970) resides at the lexeme (Jescheniak & Levelt, 1994) Simner and Smyth predict, and subsequently illustrate, that ALA exhibits no frequency effect. A problem arises, however: if ALA does not access the lexeme, how do we account for phonological priming at anaphor sites (e.g., Tanenhaus et al., 1985)? We claim that this is the result of "incidental" lemma-to-lexeme activation. Furthermore, we argue that since lexeme activation is not crucial to anaphor comprehension, anaphor reading times indicate lemma search times only (therefore there is no frequency effect). An experiment is presented demonstrating that lemma-access during ALA can cause incidental lexeme activation without invoking a frequency effect.     

Phonological processing during silent reading in aphasic patients

In a task involving the detection of a predesignated letter during the silent reading of a series of passages, left-brain-damaged aphasic patients and right-brain-damaged patients showed patterns of performance consistent with those of normal individuals. Both of the brain-damaged groups were more likely to detect letters when they were pronounced in a typical way (e.g., g in "ago") than in an atypical way (e.g., g in "through"), suggesting the use of phonological recoding during silent reading. In addition, both of these groups were more likely to detect letters when they occurred in content than in function words, suggesting a differential processing of these word types. Possible differences in the strategies predominantly relied on for phonological recoding and for the differential processing of content and function words by different groups of patients are discussed.     

Planning at the Phonological Level during Sentence Production

In two picture–word interference experiments we examined whether phrase boundaries affected how far in advance speakers plan the sounds of words during sentence production. Participants produced sentences of varying lengths (short determiner + noun + verb or long determiner + adjective + noun + verb) while ignoring phonologically related and unrelated words to the verb of the sentence. Response times to begin producing both types of sentences were faster in the presence of a related versus unrelated distractor. The results suggest that the activation of phonological properties of words outside the first phrase and first and second phonological word affect onset of articulation during sentence production. The results are discussed in the light of previous evidence of phonological planning during multi-word production. Implications for the phonological facilitation effect in the picture–word interference paradigm are also discussed.The research reported in this article served as partial fulfillment of the requirements for the PhD degree at Harvard University for Tatiana T. Schnur     

Manipulation of voice onset time during dichotic listening

The manipulation of voice onset time (VOT) during dichotic listening has provided novel insights regarding brain function. To date, the most common design is the utilisation of four VOT conditions: short-long pairs (SL), where a CV syllable with a short VOT is presented to the left ear and a CV syllable with a long VOT is presented to the right ear as well as long-short (LS), short-short (SS) and long-long (LL) pairs. Rimol, Eichele, and Hugdahl (2006) first reported that in healthy adults SL pairs elicit the largest REA while, in fact, LS pairs elicit a significant left ear advantage (LEA). This VOT effect was replicated by Sandmann et al. (2007). A study of children aged 5-8years of age has shown a developmental trajectory whereby long VOTs gradually start to dominate over short VOTs when LS pairs are being presented under dichotic conditions (Westerhausen, Helland, Ofte, & Hugdahl, 2010). Two studies have investigated attentional modulation of the VOT effect in children and adults. The converging evidence from these studies shows that at around 9years of age children lack the adult-like cognitive flexibility required to exert top-down control over stimulus-driven bottom-up processes (Andersson, Llera, Rimol, & Hugdahl, 2008; Arciuli, Rankine, & Monaghan, 2010). Arciuli et al. further demonstrated that this kind of cognitive flexibility is a predictor of proficiency with complex tasks such as reading. A review of each of these studies, the possible mechanisms underlying the VOT effect and directions for future research are discussed.     

Phonological activation of category coordinates during speech planning is observable in children but not in adults: evidence for cascaded processing

There is a long-standing debate in the area of speech production on the question of whether only words selected for articulation are phonologically activated (as maintained by serial-discrete models) or whether this is also true for their semantic competitors (as maintained by forward-cascading and interactive models). Past research has addressed this issue by testing whether retrieval of a target word (e.g., cat) affects--or is affected by--the processing of a word that is phonologically related to a semantic category coordinate of the target (e.g., doll, related to dog) and has consistently failed to obtain such mediated effects in adult speakers. The authors present a series of experiments demonstrating that mediated effects are present in children (around age 7) and diminish with increasing age. This observation provides further evidence for cascaded models of lexical retrieval.     

The time course of orthographic and phonological code activation

The present study used event-related potentials (ERPs) to examine the time course of orthographic and phonological priming in the masked priming paradigm. Participants monitored visual target words for occasional animal names, and ERPs to nonanimal critical items were recorded. These critical items were preceded by different types of primes: Orthographic priming was examined using transposed-letter (TL) primes (e.g., barin-BRAIN) and their controls (e.g., bosin-BRAIN); phonological priming was examined using pseudohomophone primes (e.g., brane-BRAIN) and their controls (e.g., brant-BRAIN). Both manipulations modulated the N250 ERP component, which is hypothesized to reflect sublexical processing during visual word recognition. Orthographic (TL) priming and phonological (pseudohomophone) priming were found to have distinct topographical distributions and different timing, with orthographic effects arising earlier than phonological effects.     

Phonological false recognition produced by bottom-up automatic activation in young and older people

ABSTRACT

Two experiments explored a new procedure to implicitly induce phonological false memories in young and older people. On the study tasks, half of the words were formed from half of the letters in the alphabet, whereas the remaining words were formed from all the letters in the alphabet. On the recognition tests, there were three types of non-studied new words: critical lures formed from the same half of the letters as the studied words; distractors formed from the other half of the letters not used, and distractors formed from all the letters in the alphabet. In both experiments, the results showed that, in both young and older people, critical lures produced more false recognitions than distractors composed of all the letters in the alphabet, which, in turn, produced more false alarms than distractors composed of the letters not used during the study. These results support the predictions of the activation/monitoring models, which assume that false memories are partly due to activation spreading from items (semantically or phonologically) related to the critical words.     

Phonological effects in visual word recognition: investigating the impact of feedback activation

P. M. Pexman, S. J. Lupker, and D. Jared (2001) reported longer response latencies in lexical decision tasks (LDTs) for homophones (e.g., maid) than for nonhomophones, and attributed this homophone effect to orthographic competition created by feedback activation from phonology. In the current study, two predictions of this feedback account were tested: (a) In LDT, observe homophone effects should be observed but not regularity or homograph effects because most exception words (e.g., pint) and homographs (e.g., wind) have different feedback characteristics than homophones do, and (b) in a phonological LDT ("does it sound like a word?"), regularity and homograph effects should be observed but not homophone effects. Both predictions were confirmed. These results support the claim that feedback activation from phonology plays a significant role in visual word recognition.     

On spatial response code activation in a Simon task

The Simon effect refers to the performance advantage for trials where the task-irrelevant location of a target spatially corresponds with the location of the response. It is thought that the irrelevant spatial code of the target facilitates responding by automatically pre-activating the spatially corresponding response code. This spatial code is thought to passively decay shortly after its activation. In this investigation, the response was selected according to the identity of a central cue. The selected response was executed or withheld depending the identity (Experiment 1) or the presence (Experiment 2) of the target. Varying the stimulus-onset asynchrony (SOA), between the central response cue and the peripheral target, allowed for a time-course analysis of the Simon effect. The results of two experiments provided no indication that the activation level of the irrelevant spatial code decayed while the relevant response was prepared. Although reaction times increased as the SOA decreased, the Simon effect was additive with SOA, suggesting that the automatic activation of the task-irrelevant spatial code was delayed until the task-relevant response code was mostly prepared, perhaps due to the capacity limitations of response selection.     

Phonological representation of words in working memory during sentence reading

The temporal dynamics of a visual target word’s phonological representation was examined by presentation of an irrelevant spoken companion word when the participant’s eyes reached the target’s location during sentence reading. The spoken word was identical, similar, or dissimilar to the phonological specification of the visual target. All spoken words increased the time spent viewing the target, with larger effects in thesimilar anddissimilar spoken word conditions than in theidentical condition. The reading of posttarget text was disrupted when the spoken word was similar but not when it was identical or dissimilar to the target. Phonological interference indicates that a word’s phonological representation remains active after it has been identified during sentence reading.     

Phonological spelling

A case study is presented of phonological spelling, an acquired spelling disorder in which the primary symptom is the occurrence of phonologically plausible errors (e.g. "flood" → flud). Not all of the patient's spelling errors are as phonologically "perfect" as this example; but it is arguable that the errors primarily derive from a routine which segments a phonological code and assigns orthographic representations to these individual segments. This account of errors in phonological spelling is contrasted with an interpretation of oral reading errors in surface dyslexia. We conclude that errors in the two disorders do not reveal a precise parallel, and that the contrast is partly attributable to the differential role of comprehension in reading and spelling.     

The generation of temporal and melodic expectancies during musical listening

When listening to a melody, we are often able to anticipate not onlywhat tonal intervals will occur next but alsowhen in time these will appear. The experiments reported here were carried out to investigate what types of structural relations support the generation of temporal expectancies in the context of a melody recognition task. The strategy was to present subjects with a set of folk tunes in which temporal accents (i.e., notes with a prolonged duration) always occurred in the first half of a melody, so that expectancies, if generated, could carry over to an isochronous sequence of notes in the latter half ofthe melody. The ability to detect deviant pitch changes in the final variation as a function of rhythmic context was then evaluated. Accuracy and reaction time data from Experiment 1 indicated that expectancy formation jointly depends on an invariant periodicity of temporal accentuation and the attentional highlighting ofcertain melodic relations (i.e., phrase ending points). In Experiment 2, once these joint expectancies were generated, the temporal dimension had a greater facilitating effectupon melody recognition than did the melodic one. These results are discussed in terms of their implications for the perceptual processing of musical events.     

Distractor clustering enhances detection speed and accuracy during selective listening

The effects of distractor clustering on target detection were examined in two experiments in which subjects attended to binaural tone bursts of one frequency while ignoring distracting tones of two competing frequencies. The subjects pressed a button in response to occasional target tones of longer duration (Experiment 1) or increased loudness (Experiment 2). In evenly spaced conditions, attended and distractor frequencies differed by 6 and 12 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1048-Hz distractors). In clustered conditions, distractor frequencies were grouped; attended tones differed from the distractors by 6 and 7 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1400-Hz distractors). The tones were presented in randomized sequences at fixed or random stimulus onset asynchronies (SOAs). In both experiments, clustering of the unattended frequencies improved the detectability of targets and speeded target reaction times, Similar effects were found at fixed and variable SO As. Results from the analysis of stimulus sequence suggest that clustering improved performance primarily by reducing the interference caused by distractors that immediately preceded the target.     

Dichotic listening during forced-attention in a patient with left hemispherectomy

A young left-handed girl with an extensive posttraumatic lesion in the left hemisphere was tested with dichotic listening (DL) under three different attentional instructions. The major aim of the study was to evaluate a structural vs attentional explanation for dichotic listening. As both her expressive and receptive language functions were intact after the lesion, it was assumed that the right hemisphere was the language-dominant one. In the free-report condition, she was free to divert attention to and to report from both ear inputs. In the forced-right condition, she was instructed to attend to and report only from the right ear input. In the forced-left condition, she was instructed to attend to and to report only from the left-ear input. Her performance was compared with data from a previously collected sample of normal left-handed females. Analysis showed that the patient, in contrast to the normal sample, revealed a complete right-ear extinction phenomenon, irrespective of attentional instruction. Furthermore, she showed superior correct reports from the left ear, compared with those of the normal sample, also irrespective of attentional instruction. It is concluded that these results support a structural, rather than attentional explanation for the right-ear advantage (REA) typically observed in dichotic listening. The utility of validating the dichotic listening technique on patients with brain lesions is discussed.     

Auditory evoked potentials during selective listening to dichotic speech messages

The sensitivity of the scalp-recorded, auditory evoked potential to selective attention was examined while subjects monitored one of two dichotically presented speech passages for content. Evoked potentials were elicited to irrelevant probe stimuli (vowel sounds) embedded in both the right- and the leftear’s message. The amplitude of the evoked potential was larger to probe stimuli embedded in the attended message than to probe stimuli in the unattended message. Recall performance was unaffected by the presence of the probes. The results are interpreted as supporting the hypothesis that this evoked potential sensitivity reflects an initial “input selection” stage of attention.