[Show abstract][Hide abstract] ABSTRACT: The question of whether sensitivity peaks at vowel boundaries (i.e., phoneme boundary effects) and sensitivity minima near
excellent category exemplars (i.e., perceptual magnet effects) stem from the same stage of perceptual processing was examined
in two experiments. In Experiment 1, participants gave phoneme identification and goodness ratings for 13 synthesized English
/ i / and /e / vowels. In Experiment 2, participants discriminated pairs of these vowels. Either the listeners discriminated
the entire range of stimuli within each block of trials, or the range within each block was restricted to a single stimulus
pair. In addition, listeners discriminated either one-step or two-step intervals along the stimulus series. The results demonstrated
that sensitivity peaks at vowel boundaries were more influenced by stimulus range than were perceptual magnet effects; peaks
in sensitivity near the /i/-/e/ boundary were reduced with restricted stimulus ranges and one-step intervals, but nüfüma in
discrimination near the best exemplars of /i/ were present in all conditions.
[Show abstract][Hide abstract] ABSTRACT: A major focus of recent attempts to enhance cochlear implant (CI) systems has been to increase the rate at which pulses are delivered to the electrode array. One basis for these attempts has been the expectation that faster stimulation rates would lead to an enhanced representation of temporal modulation information. However, there is recent physiological and behavioral evidence to suggest that the reverse may be the case. Here, the effects of stimulation rate on the perception of amplitude modulation were assessed using both modulation detection and modulation frequency discrimination tasks for a range of pulse rates extending considerably higher than the highest rate tested in previous studies and for different speech-relevant modulation frequencies.
Detection of sinusoidal amplitude modulation was assessed in five CI users using monopolar pulse trains presented to a single electrode at rates of 482, 723, 1447, 2894, and 5787 pulses per second (pps). Adaptive procedures were used to find the minimal detectable modulation depth at modulation frequencies of 10 and 100 Hz and at carrier levels of 25%, 50%, and 75% of the electrode's dynamic range. Discrimination of modulation frequency was examined for the same range of pulse rates for the highest carrier level. Similar adaptive procedures determined the minimum increase in modulation frequency that could be detected relative to reference modulation frequencies of 10, 100, and 200 Hz. In both tasks, level roving was implemented to minimize possible loudness cues.
Consistent with previous evidence, modulation detection thresholds were better for higher carrier levels and lower modulation frequencies. When modulation depth at threshold was expressed in terms of the ratio of the depth of the modulation and the carrier level in dB (i.e., 20 log m), performance was significantly better at lower pulse rates. However, when modulation depth was expressed relative to dynamic range, the effect of pulse rate was no longer significant, reflecting the fact that dynamic range increases with pulse rate. Modulation frequency discrimination clearly worsened with increasing modulation frequency, but there was no significant effect of pulse rate.
In contrast to some recent evidence, no clearly harmful effect of higher pulse rates on modulation perception was found. However, even with very fast stimulation rates, tested over a wide range of modulation frequencies and with two different tasks, there is no evidence of benefit from faster stimulation rates in the perception of amplitude modulation.
[Show abstract][Hide abstract] ABSTRACT: This paper presents an interpretation of inconsistent remarks which subjects made in explaining their erroneous solutions to a difficult deductive problem. Four half-masked cards of the following types were presented: (a) a number in the lower half, (b) a blank in the upper half, (c) a letter in the upper half, and (d) a blank in the lower half. The problem is to say which cards need to be unmasked to determine decisively whether a sentence like ‘A letter is above each number’ is true or false. The original aim was to determine the possible effects of varying the order of the terms in the test sentence: the results were inconclusive. However, the subjects' protocols were of much greater interest. When asked to justify their incorrect solutions, their remarks clearly revealed the operation of irreversible thought processes. Three possible hypotheses about them are considered, and it is argued that one involving dissociation of attention is most plausible.
British Journal of Psychology. 04/2011; 65(4):537 - 546.
[Show abstract][Hide abstract] ABSTRACT: An inferential task was investigated in which the subjects had to select which of four cards they needed to inspect in order to determine whether a rule was true or false. In one condition crucial information was concealed on the other side of the cards, and in another condition it was on the same side of the cards, but covered by a mask. A previous experiment suggested that subjects sometimes confused the notion of ‘the other side of the card’. But no difference was found between these two conditions. Only two out of the 36 subjects initially made the correct selection.An attempt was made subsequently to enable the subjects to correct their errors by asking them to evaluate the cards in relation to the rule. When a conflict occurred between the selection of the cards and their evaluation, some insight was gained. In other cases these two processes passed one another by, in spite of the fact that this involved self-contradiction.
British Journal of Psychology. 04/2011; 61(4):509 - 515.
[Show abstract][Hide abstract] ABSTRACT: ABSTRACT This paper stresses the need to refer to normal control data when assessing children with speech disorders. It is based on the findings of a completed, one-year, full-time research project designed to investigate the normal development of speech, auditory and rhyme skills within a psycholinguistic framework (Stackhouse & Wells, 1993). The aim of the project was to examine phonological processing skills in normally developing children for comparison with children presenting with speech, lexical and literacy disorders. A range of tasks was presented to 100 normally developing children, aged 3–7 years. The tasks included auditory discrimination, rhyme judgement, detection and production; speech repetition, naming and continuous speech. The tasks were presented in both visual and auditory modalities, and both real and non-word stimuli were used. For each set of tasks stimuli were identical or closely matched, using phonetic criteria. Data was analysed for subjects within each age band, i.e. 3-year-olds, 4-year-olds, 5-year-olds, 6-year-olds and 7-year-olds. Analysis of variance revealed significant effects of age on all tasks. Comparisons were made of performance across the different presentations and stimuli-type relevant to each task and significant effects of presentation and stimuli-type were found for some tasks but not for all comparisons made. These findings allowed us to present a profile of normal development in performance across a range of input and output processing tasks. The time constraint prevents the full profile of results being included. However, the implications of the results for clinical practice will be presented. For example, given that normally developing children find non-word repetition more difficult than real-word repetition, at what point is the difference in performance on these tasks indicative of a motor programming deficit? Further, given the relationship between rhyme detection and production skills in normally developing children, at what age is the failure to produce any rhyming words significant? In summary, this study identified typical developmental profiles of phonological processing skills in children of 3–7 years of age. Speech and language therapists can use these results to identify with greater accuracy children with speech and language difficulties who may present with atypical psycholinguistic profiles. Subsequent therapy can be targeted in a more precise way.
International Journal of Language & Communication Disorders 04/2011; 30(S1):287 - 293.
[Show abstract][Hide abstract] ABSTRACT: Beyond modularity attempts a synthesis of Fodor's anticonstructivist nativism and Piaget's antinativist constructivism. Contra Fodor, I argue that: (1) the study of cognitive development is essential to cognitive science, (2) the module/central processing dichotomy is too rigid, and (3) the mind does not begin with prespecified modules; rather, development involves a gradual process of “modularization.” Contra Piaget, I argue that: (1) development rarely involves stagelike domain-general change and (2) domainspecific predispositions give development a small but significant kickstart by focusing the infant's attention on proprietary inputs. Development does not stop at efficient learning. A fundamental aspect of human development (“representational redescription”) is the hypothesized process by which information that is in a cognitive system becomes progressively explicit knowledge to that system. Development thus involves two complementary processes of progressive modularization and progressive “explicitation.” Empirical findings on the child as linguist, physicist, mathematician, psychologist, and notator are discussed in support of the theoretical framework. Each chapter concentrates first on the initial state of the infant mind/brain and on subsequent domain-specific learning in infancy and early childhood. It then goes on to explore data on older children's problem solving and theory building, with particular focus on evolving cognitive flexibility. Emphasis is placed throughout on the status of representations underlying different capacities and on the multiple levels at which knowledge is stored and accessible. Finally, consideration is given to the need for more formal developmental models, and a comparison is made between representational redescription and connectionist simulations of development. In conclusion, I consider what is special about human cognition by speculating on the status of representations underlying the structure of behavior in other species.
International Journal of Language & Communication Disorders 03/2011; 29(1):95 - 105.
[Show abstract][Hide abstract] ABSTRACT: In this paper I argue that English clefts are an example of an apparent syntax/semantics mismatch, in that the cleft clause (the relative clause appearing at the end of the matrix clause) semantically modifies the initial pronoun it, but syntactically modifies (that is, is underlyingly adjoined to) the clefted XP, as proposed by Hedberg (2000). This renders suspect both ‘specificational analyses’, on which the cleft clause both semantically and syntactically modifies it, and ‘expletive analyses’, on which the cleft clause and clefted XP are both semantically and syntactically composed directly. I provide new evidence for Hedberg's type of analysis. The first set of evidence suggests that cleft it is non-expletive, thus arguing in favour of treating it and the cleft clause as a discontinuous definite description. The second set of evidence shows that, with respect to various tests, the cleft clause behaves as if the clefted XP, rather than it, is its antecedent.
[Show abstract][Hide abstract] ABSTRACT: Voice is a dominant component of everyday speech in all languages. The possibility is examined that its use may have evolved so that its timing in connected speech is ideal from the point of view of information theory-with voicing taking up 50% of the total speaking time. Initial measurements have been made of voice timing proportions using Laryngograph (EGG) signals as the basis of timing analyses. The results of these analyses for data from two groups of speakers are reported: single native speakers of each of 8 different languages; and 56 speakers of British English. The average 51% and 52% voice timing proportions that were found closely approximate the ideal of 50%. Implications of this finding for voice evolution are briefly discussed.
[Show abstract][Hide abstract] ABSTRACT: The study investigated language and developmental factors in the use of visual information in audiovisual speech perception in speakers from different language backgrounds. Mandarin-Chinese and English adults and 8- to 9-year-old children were presented with /ba/, /da/, and /ga/ tokens spoken by two English and two Mandarin-Chinese speakers. A syllable identification task was presented in auditory-only, visual-only, and audiovisual (congruent and incongruent) conditions in clear and in noise. The results showed an increase in the use of visual information in adults relative to children in both the Chinese and English groups. In addition, a positive correlation between the total visual effect and speechreading performance was found, suggesting that the smaller visual influence in the bimodal condition for children might be accounted by their less sophisticated speechreading ability. In regard to the language factor, it was found that Chinese perceivers use visual information in their audiovisual speech processing to the same extent as English perceivers. Finally, there was evidence for a "non-native speaker effect" (i.e., stronger visual effect for non-native speech stimuli), but only for the English participants. Results from the current study suggest that the visual appearance of individual speakers and the acoustic-phonetic properties of specific languages should be considered in future cross-language studies.
The Journal of the Acoustical Society of America 09/2009; 126(2):858-65.
[Show abstract][Hide abstract] ABSTRACT: This paper sets out to investigate the relative role of Voice Onset Time (VOT) and fundamental frequency in a language with lexical tone. By comparing English and the Chadic language Kera, this study explores the interaction between the production and perception of voicing and the role played by voicing in the phonological structure of the language. The major finding is that the role of VOT and F0 in the perception of voicing differs dramatically between English and Kera subjects with English subjects relying mainly on VOT and Kera subjects mainly on F0. The phonological implications of these results for Kera are that tone is contrastive while voicing is not, which is the reverse of English. I will propose that Kera has no [voice] feature, and that the variation in VOT plays a role as a supporting cue to tone, although the exact amount of VOT usage in Kera production and perception differs depending on the amount of contact with French. The dominance of tone suggests that despite claims that Kera exhibits long-distance voice spreading, what spreads is in fact tone rather than voice.
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