Primates appear to be motorically capable of speaking words insofar as they can articulate sounds and have (in some documented instances) actually articulated “words.” For example, rhesus monkeys produce different call types in association with ad hoc visual signals and even switch between call types associated with different signals (Hage & Nieder Reference Hage and Nieder2013). So, vocal tract morphology is not the only limitation that accounts for the inability of nonhuman primates to produce even simple verbal utterances.
Contemporary developmental theory and research – language production included – are rooted in systems dynamics of individual-context relations that guide the emergence of behavior and ontogenetic change. Development is associated with dynamic reciprocal relations among structures at multiple levels of organization. Language – in toto, comprehension and expression of phonology, morphology, semantics, syntactics, and pragmatics, at least – has such a multilevel organization, extending as it does from the anatomy of the vocal tract through brain-based motor effectors to interpersonal dynamics and on to cultural experience. By focusing on one level of analysis, Ackermann et al.'s hypothesis misses the essential multilevel and developmental nature of vocal production. Bidirectional influences operate across these multiple levels as biological and cognitive systems are nested within individuals, and individuals are nested within complex social and verbal environments. Accordingly, the developmental systems perspective leads away from a singular explanatory focus on organism or on context to how multiple forces, which span from biological pathways to macrolinguistic influences, collaborate in development.
Taking a cue from advances in developmental science, consider two levels above the Ackermann et al.'s focus on vocal tract morphology that may play vital roles in vocal/verbal production. Primates may be lacking in higher-order cognitive-linguistic operations that subserve communicative skills and in social interaction experiences that play key roles in speech development.
Ackermann et al. focus on ontogenetic speech production in interactions between basal ganglia at one end of the spectrum and their cortical targets at the other. Their main argument titularly focuses on the roots and limiting conditions of vocal/verbal production but seems crucially to omit from consideration comprehension, which almost by law ontogenetically and cognitively precedes production and therefore places a higher-order limitation on production. The case of human children acquiring language tells us that, outside cry, laugh, and mimicry, “context-restricted” and “context-free” expressions of verbal forms follow comprehension of those forms. Production hardly ever occurs without comprehension as a pre-requisite.
Comprehension qua cognition transcends genetic endowment. Ackermann et al. argue that, because primates lacking the (human) FOXP2 variant cannot even imitate simple speech-like utterances, and because the disruption of this gene in humans gives rise to severe articulatory deficits, it appears warranted to assume that the human variant of this gene locus is pre-requisite to the phylogenetic emergence of articulate speech. From a developmental viewpoint, however, it is well to recall that human babies who are also speechless presumably possess the FOXP2 gene. Like primates, older infants possess the requisite genetics and neuroanatomy; what they lack, like primates, are cognition and (see below) requisite experience. Here, multilevel development is uncoupled from neuroanatomy and pathology.
Ackermann et al. assert that vocalizations in nonhuman species reflect ontogenetic modifications of acoustic structure rooted in maturation. However, the restriction to maturation again acknowledges only one level of understanding speechlessness in nonhuman primates. Contemporary interactionist models posit that social factors shape human communicative development and early language learning. Communication begins as the product of bidirectional influences between infants and adults. When 9- to 10-month-old English-learning infants experienced a non-native language (Mandarin) through live interactions with adults, television, or audio-only presentations, only those infants who experienced the language through live interactions learned (Kuhl et al. Reference Kuhl, Tsao and Liu2003). Similarly, children learn novel verbs during either live interactions or socially contingent video training over video chat, but not during non-contingent video training (Roseberry et al. Reference Roseberry, Hirsh-Pasek and Golinkoff2014). Human children's caregivers provide feedback that is vital to infant learning. Furthermore, prospective longitudinal study shows that maternal responsiveness to infants predicts when children achieve various language milestones (Bornstein et al. Reference Bornstein, Tamis-LeMonda and Haynes1999; Tamis-LeMonda et al. Reference Tamis-LeMonda, Bornstein, Baumwell and Damast1996). In human beings, experiences make a telling difference. Recall that 100% of meaningful vocalizations (the lexicon) are learned: Children growing up in Boston learn English-sounding vocal patterns, whereas children growing up in Paris learn French-sounding ones.
These assertions are further supported by understanding what happens when caregivers cannot adequately interpret a child's vocalization and provide adequate feedback. An instructive example occurs when a parent interacts with a child who has a neurological deficit before the deficit is diagnosed, as in the case of children with autism for whom diagnoses are provided after 18–24 months of age. A core deficit of autism occurs in social communication. At least in a subgroup of infants with autism, early vocalizations are atypically produced (Esposito et al. Reference Esposito, del Carmen Rostagno, Venuti, Haltigan and Messinger2013; Sheinkopf et al. Reference Sheinkopf, Iverson, Rinaldi and Lester2012), making it challenging for caregivers to interpret (Venuti et al. Reference Venuti, Caria, Esposito, De Pisapia, Bornstein and de Falco2012) and respond to their child in an effective way (Esposito & Venuti Reference Esposito and Venuti2009).
In summary, Ackermann et al. point to anatomy and neurobiology as rate limiting factors on vocal/verbal production, when it is also the case that language cognition and interactional experience need to be added to neuroanatomical machinery. As language is a multilevel phenomenon, it is good to have one level of the multilevel system better understood, but all levels as well as their interconnectivity need to be analyzed and apprehended. The authors conclude that “birdsong can serve as an experimental model for the investigation of the neural control of human speech” (sect. 6), and this might be the case for the neural control level, but for levels of the complete system above neuroanatomy, including syntactic and semantic aspects of verbal utterances, higher-order cognitions and linguistic experience are requisite. The ultimate goal of the effort here is purportedly to appreciate comprehensively the origins, capacities, and motives of human speech.
The stated aim of Ackermann et al. is to propose phylogenetic stages of speech acquisition which they root in “monosynaptic refinement of corticobulbar tracts and laryngeal elaboration of cortico-striatal motor circuits” (sect. 7, para. 1). This approach leaves untouched virtually all of the higher-order components of mental functioning and social language learning that collaborate in the end state of verbal production.
Primates appear to be motorically capable of speaking words insofar as they can articulate sounds and have (in some documented instances) actually articulated “words.” For example, rhesus monkeys produce different call types in association with ad hoc visual signals and even switch between call types associated with different signals (Hage & Nieder Reference Hage and Nieder2013). So, vocal tract morphology is not the only limitation that accounts for the inability of nonhuman primates to produce even simple verbal utterances.
Contemporary developmental theory and research – language production included – are rooted in systems dynamics of individual-context relations that guide the emergence of behavior and ontogenetic change. Development is associated with dynamic reciprocal relations among structures at multiple levels of organization. Language – in toto, comprehension and expression of phonology, morphology, semantics, syntactics, and pragmatics, at least – has such a multilevel organization, extending as it does from the anatomy of the vocal tract through brain-based motor effectors to interpersonal dynamics and on to cultural experience. By focusing on one level of analysis, Ackermann et al.'s hypothesis misses the essential multilevel and developmental nature of vocal production. Bidirectional influences operate across these multiple levels as biological and cognitive systems are nested within individuals, and individuals are nested within complex social and verbal environments. Accordingly, the developmental systems perspective leads away from a singular explanatory focus on organism or on context to how multiple forces, which span from biological pathways to macrolinguistic influences, collaborate in development.
Taking a cue from advances in developmental science, consider two levels above the Ackermann et al.'s focus on vocal tract morphology that may play vital roles in vocal/verbal production. Primates may be lacking in higher-order cognitive-linguistic operations that subserve communicative skills and in social interaction experiences that play key roles in speech development.
Ackermann et al. focus on ontogenetic speech production in interactions between basal ganglia at one end of the spectrum and their cortical targets at the other. Their main argument titularly focuses on the roots and limiting conditions of vocal/verbal production but seems crucially to omit from consideration comprehension, which almost by law ontogenetically and cognitively precedes production and therefore places a higher-order limitation on production. The case of human children acquiring language tells us that, outside cry, laugh, and mimicry, “context-restricted” and “context-free” expressions of verbal forms follow comprehension of those forms. Production hardly ever occurs without comprehension as a pre-requisite.
Comprehension qua cognition transcends genetic endowment. Ackermann et al. argue that, because primates lacking the (human) FOXP2 variant cannot even imitate simple speech-like utterances, and because the disruption of this gene in humans gives rise to severe articulatory deficits, it appears warranted to assume that the human variant of this gene locus is pre-requisite to the phylogenetic emergence of articulate speech. From a developmental viewpoint, however, it is well to recall that human babies who are also speechless presumably possess the FOXP2 gene. Like primates, older infants possess the requisite genetics and neuroanatomy; what they lack, like primates, are cognition and (see below) requisite experience. Here, multilevel development is uncoupled from neuroanatomy and pathology.
Ackermann et al. assert that vocalizations in nonhuman species reflect ontogenetic modifications of acoustic structure rooted in maturation. However, the restriction to maturation again acknowledges only one level of understanding speechlessness in nonhuman primates. Contemporary interactionist models posit that social factors shape human communicative development and early language learning. Communication begins as the product of bidirectional influences between infants and adults. When 9- to 10-month-old English-learning infants experienced a non-native language (Mandarin) through live interactions with adults, television, or audio-only presentations, only those infants who experienced the language through live interactions learned (Kuhl et al. Reference Kuhl, Tsao and Liu2003). Similarly, children learn novel verbs during either live interactions or socially contingent video training over video chat, but not during non-contingent video training (Roseberry et al. Reference Roseberry, Hirsh-Pasek and Golinkoff2014). Human children's caregivers provide feedback that is vital to infant learning. Furthermore, prospective longitudinal study shows that maternal responsiveness to infants predicts when children achieve various language milestones (Bornstein et al. Reference Bornstein, Tamis-LeMonda and Haynes1999; Tamis-LeMonda et al. Reference Tamis-LeMonda, Bornstein, Baumwell and Damast1996). In human beings, experiences make a telling difference. Recall that 100% of meaningful vocalizations (the lexicon) are learned: Children growing up in Boston learn English-sounding vocal patterns, whereas children growing up in Paris learn French-sounding ones.
These assertions are further supported by understanding what happens when caregivers cannot adequately interpret a child's vocalization and provide adequate feedback. An instructive example occurs when a parent interacts with a child who has a neurological deficit before the deficit is diagnosed, as in the case of children with autism for whom diagnoses are provided after 18–24 months of age. A core deficit of autism occurs in social communication. At least in a subgroup of infants with autism, early vocalizations are atypically produced (Esposito et al. Reference Esposito, del Carmen Rostagno, Venuti, Haltigan and Messinger2013; Sheinkopf et al. Reference Sheinkopf, Iverson, Rinaldi and Lester2012), making it challenging for caregivers to interpret (Venuti et al. Reference Venuti, Caria, Esposito, De Pisapia, Bornstein and de Falco2012) and respond to their child in an effective way (Esposito & Venuti Reference Esposito and Venuti2009).
In summary, Ackermann et al. point to anatomy and neurobiology as rate limiting factors on vocal/verbal production, when it is also the case that language cognition and interactional experience need to be added to neuroanatomical machinery. As language is a multilevel phenomenon, it is good to have one level of the multilevel system better understood, but all levels as well as their interconnectivity need to be analyzed and apprehended. The authors conclude that “birdsong can serve as an experimental model for the investigation of the neural control of human speech” (sect. 6), and this might be the case for the neural control level, but for levels of the complete system above neuroanatomy, including syntactic and semantic aspects of verbal utterances, higher-order cognitions and linguistic experience are requisite. The ultimate goal of the effort here is purportedly to appreciate comprehensively the origins, capacities, and motives of human speech.
The stated aim of Ackermann et al. is to propose phylogenetic stages of speech acquisition which they root in “monosynaptic refinement of corticobulbar tracts and laryngeal elaboration of cortico-striatal motor circuits” (sect. 7, para. 1). This approach leaves untouched virtually all of the higher-order components of mental functioning and social language learning that collaborate in the end state of verbal production.