Evolution of the strongest vertebrate rightward action asymmetries: Marine mammal sidedness and human handedness.

Marine mammals and humans have the strongest manifestations of what is apparently a vertebrate-wide tendency toward a rightward action asymmetry associated with routine behavior. Marine mammal asymmetries usually involve whole-body actions associated with feeding. The human-like strength of these asymmetries may result from a problem of external aquatic support for the reactive component of the demanding lateral maneuvers of large marine mammals in daily pursuit of prey. Our asymmetrical primate heritage may also have begun with a rightward whole-body asymmetry, in prosimians, perhaps also resulting from problems of support for the reactive component of action; in this case arising from the arboreal habitat (and paradoxically including left-handedness). Monkeys and apes (simians) subsequently added right-sided adaptations for manipulation, bimanual coordination, bipedalism, throwing, and manual communication, most importantly by distal elaboration of limb function. The strength of human right-handedness may result partly from further elaboration of these simian action adaptations and partly from an evolving cognitive superstructure for tool use and language.

Vertebrate whole-body-action asymmetries and the evolution of right handedness: a comparison between humans and marine mammals.

As part of a vertebrate-wide trend toward left brain/right side asymmetries in routine whole-body actions, marine mammals show signs of rightward appendage-use biases, and short- and long-term turning asymmetries most of which are unique in non-humans in being just as strong as right handedness, and even stronger than human handedness-related turning biases. Short-term marine mammal turning asymmetries and human about-turning asymmetries share a leading right side, suggesting a commonality in left hemisphere intentional control. The long-term leftward turning bias that both groups share may be an indirect result of both sensory and motor influences on the right side in dolphins, but be induced by a right-hemisphere-controlled spatial/attentional bias to the left in humans. Marine mammals may share, with humans and other higher primates, a left hemisphere specialization for action dynamics, although evidence is currently lacking for human-like right hemisphere specializations relevant to action in other vertebrates.

Accuracy of consonant-vowel syllables in young cochlear implant recipients and hearing children in the single-word period.

PURPOSE: Attaining speech accuracy requires that children perceive and attach meanings to vocal output on the basis of production system capacities. Because auditory perception underlies speech accuracy, profiles for children with hearing loss (HL) differ from those of children with normal hearing (NH). METHOD: To understand the impact of auditory history on emergence of speech capacities, the authors compared consonant-vowel (CV) syllable accuracy in early words in 4 NH children and 4 children with HL who received cochlear implantation (CI) before age 2 years. Participants were video-recorded monthly for 6 months following word onset. CV vocalizations were coded perceptually with broad phonetic transcription. Observed-to-expected ratios of CV productions and accuracy were tested with chi-square analysis. An ordered multinomial model tested level of accuracy, including both accuracy and error patterns. RESULTS: Most frequently produced sequences were most accurately produced across group and time. NH children were more accurate overall than children with CI. Both groups improved accuracy over time by decreasing partially accurate productions (accurate consonant-inaccurate vowel). Both groups favored CV patterns with compatible place of articulation between consonant and vowel in absolute frequency and level of accuracy. CONCLUSION: Differences in emergence of CV syllable accuracy arise from differences in auditory perception between the NH and CI groups.

Segmental properties of input to infants: a study of Korean.

Segmental distributions of Korean infant-directed speech (IDS) and adult-directed speech (ADS) were compared. Significant differences were found in both consonant and vowel patterns. Korean-speaking mothers using IDS displayed more frequent labial consonantal place and less frequent coronal and glottal place and fricative manner. They showed more use of mid and low central vowels in IDS as well as more use of language-specific Korean phonemes. Mothers produced significantly more fortis and geminate and less lenis consonant phonemes in IDS than in ADS. Findings suggest that Korean mothers speaking to infants in the IDS speech style use sounds that more closely match infant production propensities as well as highlighting perceptually salient properties. IDS may serve to facilitate infant learning of ambient language phonological regularities.

Frame dominance in infants with hearing loss.

PURPOSE: According to the frames then content (f/c) hypothesis (P. F. MacNeilage & B. L. Davis, 1990), the internal structure of syllables with consonant plus vowel structure (CV) during canonical babbling is determined primarily by production system properties related to rhythmic mandibular oscillations (motor frames). The purpose of this study was to evaluate whether auditory sensitivity affects the internal organization of CV syllables in infants identified in the 1st year of life with hearing loss. METHOD: CV co-occurrence patterns were analyzed for 13 infants with varying degrees of hearing sensitivity (normal hearing [n = 4], mild-to-moderately severe hearing loss (n = 6), and severe-to-profound hearing loss [n = 3]). Consonants and vowels within CV syllables were grouped according to place of articulation. Thus, an inventory of CV syllables with labial, coronal, and dorsal consonant onsets was created. RESULTS: 77% of predicted frames were confirmed above chance. Additionally, there was no association between pure-tone average and any CV co-occurrence. Finally, co-occurrences that were not predicted by the hypothesis were statistically confirmed in very few instances. CONCLUSIONS: Auditory sensitivity may not influence intrasyllabic organization within CV syllables once infants begin canonical babbling, as the co-occurrences observed are primarily those predicted by the f/c hypothesis.

Characteristics of the rhythmic organization of vocal babbling: implications for an amodal linguistic rhythm.

Vocal babbling involves production of rhythmic sequences of a mouth close-open alternation giving the perceptual impression of a sequence of consonant-vowel syllables. Petitto and co-workers have argued vocal babbling rhythm is the same as manual syllabic babbling rhythm, in that it has a frequency of 1 cycle per second. They also assert that adult speech and sign language display the same frequency. However, available evidence suggests that the vocal babbling frequency approximates 3 cycles per second. Both adult spoken language and sign language show higher frequencies than babbling in their respective modalities. No information is currently available on the basic rhythmic parameter of intercyclical variability in either modality. A study of reduplicative babbling by 4 infants and 4 adults producing reduplicated syllables confirms the 3 per second vocal babbling rate, as well as a faster rate in adults, and provides new information on intercyclical variability.

Message and medium: Lowly and action-related origins.

Hurford presents a much-needed lowly origins scenario for the evolution of conceptual precursors to lexical items. But more is still needed on action, regarding both the message level of lexical concepts and the medium. We summarize our complementary action-based lowly origins (frame/content) scenario for the vocal auditory medium of language, which, like Hurford's scenario, is anchored in a phylogenetically old neurological dichotomy.

Acquisition of serial complexity in speech production: a comparison of phonetic and phonological approaches to first word production.

Comparison was made between performance-based and competence-based approaches to the understanding of first word production. The performance-related frame/content approach is representative of the biological/functional perspective of phonetics in seeking explanations based on motor, perceptual and cognitive aspects of speech actions. From this perspective, intrasyllabic consonant-vowel (CV) co-occurrence patterns and intersyllabic sequence patterns are viewed as reflective of biomechanical constraints emerging from mandibular oscillation cycles. A labial-coronal sequence effect involved, in addition, the problem of interfacing the lexicon with the motor system, as well as the additional problem of initiation of movement complexes. Competence-based approaches to acquisition are within the generative phonological tradition; involving an initial assumption of innate, speech-specific mental structures. While various current phonological approaches to acquisition involve consideration of sequence effects and intrasyllabic patterns, they do not adequately establish the proposed mental entities in infants of this age, and are nonexplanatory in the sense of not considering the causes of the structures and constraints that they posit.