Shari R. Baum

The neural bases of prosody: Insights from lesion studies and neuroimaging

This paper reviews the major findings and hypotheses to emerge in the literature concerned with speech prosody. Both production and perception of prosody are considered. Evidence from studies of patients with lateralized left or right hemisphere damage are presented, as well as relevant data from anatomical and functional imaging studies.

Moving toward a neuroplasticity view of bilingualism, executive control, and aging

Normal aging is an inevitable race between increasing knowledge and decreasing cognitive capacity. Crucial to understanding and promoting successful aging is determining which of these factors dominates for particular neurocognitive functions. Here, we focus on the human capacity for language, for which healthy older adults are simultaneously advantaged and disadvantaged. In recent years, a more hopeful view of cognitive aging has emerged from work suggesting that age-related declines in executive control functions are buffered by life-long bilingualism. In this paper, we selectively review what is currently known and unknown about bilingualism, executive control, and aging. Our ultimate goal is to advance the views that these issues should be reframed as a specific instance of neuroplasticity more generally and, in particular, that researchers should embrace the individual variability among bilinguals by adopting experimental and statistical approaches that respect the complexity of the questions addressed. In what follows, we set out the theoretical assumptions and empirical support of the bilingual advantages perspective, review what we know about language, cognitive control, and aging generally, and then highlight several of the relatively few studies that have investigated bilingual language processing in older adults, either on their own or in comparison with monolingual older adults. We conclude with several recommendations for how the field ought to proceed to achieve a more multifactorial view of bilingualism that emphasizes the notion of neuroplasticity over that of simple bilingual versus monolingual group comparisons.

Speech compensation to structural modifications of the oral cavity

Acoustic and perceptual analyses of vowels, stops, and fricatives produced with and without an artificial palate were conducted. Recordings were made both immediately upon insertion of the palate and following a 15-min adaptation period. Results of the acoustic analyses revealed significant alterations in the fricative spectra under conditions of perturbation with fewer, if any, changes in the vowels and stop consonants. Perceptual data confirmed these patterns and provided evidence of possible improvements in compensation over time. The data are compared to our previous studies of speech sound articulation under bite-block conditions. Differences between adaptation to modifications of oral structure (artificial palate) and oral function (jaw fixation by a bite block) are considered.

Musical Melody and Speech Intonation: Singing a Different Tune

Music and speech are often cited as characteristically human forms of communication. Both share the features of hierarchical structure, complex sound systems, and sensorimotor sequencing demands, and both are used to convey and influence emotions, among other functions [1]. Both music and speech also prominently use acoustical frequency modulations, perceived as variations in pitch, as part of their communicative repertoire. Given these similarities, and the fact that pitch perception and production involve the same peripheral transduction system (cochlea) and the same production mechanism (vocal tract), it might be natural to assume that pitch processing in speech and music would also depend on the same underlying cognitive and neural mechanisms. In this essay we argue that the processing of pitch information differs significantly for speech and music; specifically, we suggest that there are two pitch-related processing systems, one for more coarse-grained, approximate analysis and one for more fine-grained accurate representation, and that the latter is unique to music. More broadly, this dissociation offers clues about the interface between sensory and motor systems, and highlights the idea that multiple processing streams are a ubiquitous feature of neuro-cognitive architectures.

Disambiguating the ambiguity advantage effect in word recognition: An advantage for polysemous but not homonymous words

Abstract Previous lexical decision studies reported a processing advantage for words with multiple meanings (i.e., the “ambiguity advantage” effect). The present study further specifies the source of this advantage by showing that it is based on the extent of meaning relatedness of ambiguous words. Four types of ambiguous words, balanced homonymous (e.g., “panel”), unbalanced homonymous (e.g., “port”), metaphorically polysemous (e.g., “lip”), and metonymically polysemous (e.g., “rabbit”), were used in auditory and visual simple lexical decision experiments. It was found that ambiguous words with multiple related senses (i.e., polysemous words) are processed faster than frequency-matched unambiguous control words, whereas ambiguous words with multiple unrelated meanings (i.e., homonymous words) do not show such an advantage. In addition, a distinction within polysemy (into metaphor and metonymy) is demonstrated experimentally. These results call for a re-evaluation of models of word recognition, so that the advantage found for polysemous, but not homonymous, words can be accommodated.

The development of speech adaptation to an artificial palate

An investigation of adaptation to palatal modification in [s] production was conducted using acoustic and perceptual analyses. The experiment assessed whether adaptation would occur subsequent to a brief period of intensive, target-specific practice. Productions of [sa] were elicited at five time intervals, 15 min apart, with an artificial palate in place. Between measurement intervals, subjects read [s]-laden passages to promote adaptation. Results revealed improvement in both acoustic and perceptual measures at the final time interval relative to the initial measurement period. Interestingly, the data also suggested changes to normal (unperturbed) articulation patterns during the same interval. Results are discussed in relation to the development of speech adaptation to a structural modification of the oral cavity.

Production of Coronal Stops by Simultaneous Bilingual Adults.

This study investigated acoustic-phonetics of coronal stop production by adult simultaneous bilingual and monolingual speakers of Canadian English (CE) and Canadian French (CF). Differences in the phonetics of CF and CE include voicing and place of articulation distinctions. CE has a two-way voicing distinction (in syllable initial position) contrasting short-and long-lag VOT; coronal stops in CE are described as alveolar. CF also has a two-way voicing distinction, but contrasting lead and short-lag VOT; coronal stops in CF are described as dental. Acoustic analyses of stop consonants for both VOT and dental/alveolar place of articulation are reported. Results indicate that simultaneous bilingual as well as monolingual adults produce language-specific differences, albeit not in the same way, across CF and CE for voicing and place. Similarities and differences between simultaneous bilingual and monolingual adults are discussed to address phonological organization in simultaneous bilingual adults.

Acoustic analyses and perceptual data on anticipatory labial coarticulation in adults and children.

The present study investigated anticipatory labial coarticulation in the speech of adults and children. CV syllables, composed of [s], [t], and [d] before [i] and [u], were produced by four adult speakers and eight child speakers aged 3-7 years. Each stimulus was computer edited to include only the aperiodic portion of fricative-vowel and stop-vowel syllables. LPC spectra were then computed for each excised segment. Analyses of the effect of the following vowel on the spectral peak associated with the second formant frequency and on the characteristic spectral prominence for each consonant were performed. Perceptual data were obtained by presenting the aperiodic consonantal segments to subjects who were instructed to identify the following vowel as [i] or [u]. Both the acoustic and the perceptual data show strong coarticulatory effects for the adults and comparable, although less consistent, coarticulation in the speech stimuli of the children. The results are discussed in terms of the articulatory and perceptual aspects of coarticulation in language learning.

Incomplete compensation to articulatory perturbation

Measurements were made of vowels, fricatives, and stop consonants produced by 15 adult speakers of French in one free-mandible and two fixed mandible conditions. Speech acoustic data were recorded immediately upon bite-block insertion and after a 15-min accommodation period. Results indicate that compensation to increased jaw opening during speech is neither immediate nor complete as there were small but significant differences in the acoustic parameters of vowels and consonants produced under bite-block and normal conditions. Further, the data suggest that, at least for vowels, speech compensatory strategies may develop over time, perhaps involving error-based correction. Consonants appear to require a more lengthy period of speech adaptation, and this may be due to the articulatory requirements for their accurate production. Individual differences in compensatory abilities are also discussed.

Preliminary observations on the use of duration as a cue to syllable-initial fricative consonant voicing in English

Acoustic analyses were undertaken to explore the durational characteristics of the fricatives [f,theta,s,v,delta z] as cues to initial consonant voicing in English. Based on reports on the perception of voiced-voiceless fricatives, it was expected that there would be clear-cut duration differences distinguishing voiced and voiceless fricatives. Preliminary results for three speakers indicate that, although differences emerged in the overall mean duration of voiced and voiceless fricatives, contrary to expectations, there was a great deal of overlap in the duration distribution of voiced and voiceless fricative tokens. Further research is needed to examine the role of duration as a cue to syllable-initial fricative consonant voicing in English.