Program

Similarities across action and language have usually been inferred either from formal comparisons between (i) the abstract structures of language and action or (ii) from the observation that both recruit partially overlapping neural resources, especially in the inferior frontal cortex. Recent work has called these assumptions into doubt, both on formal and neuroanatomical grounds. In this talk, I will discuss the similarities and differences between language and action, mainly focusing on their differential recruitment of Brodmann Area (BA) 44 in the left Inferior Frontal Gyrus (IFG) and on what we can infer from this functional segregation.

Does tool use share syntactic processes with language? Acting with a tool is thought to add a hierarchical level into the motor plan. In the linguistic domain, syntax is the cognitive function handling interdependent elements. Using functional magnetic resonance imaging, we detected common neurofunctional substrates in the basal ganglia subserving both tool use and syntax in language. Consistent with the existence of shared neural resources, we observed bidirectional behavioral enhancement of tool use and syntactic skills in language so that training one function improves performance in the other. This reveals supramodal syntactic processes for tool use and language.

The motor constellation theory of infant phonological ontogenesis is presented. In vocal learners, auditory feedback is necessary for matching explorative vocal output against intended sound, and motor learning is facilitated by dopaminergic circuitry involving the basal ganglia and cerebellum. Phonetic fragments can thus be mapped onto corresponding motor activity constellation in laryngeal–orosensory space, enabling replicated matching over repeated vocalizations across time.

MC poses a set of assumptions: (1) human infants are born with the instinct to explore orosensory space through tactile sensory motor behavior; (2) infant babble gives rise to emergent pseudo segmental phonetic properties; (3) invariance in speech signal attributes further facilitates the acquisition of language–specific phonemic repertoires, and gives rise to phonemes proper, defined as invariants in cognitive–orosensory space; (4) babble is thus gradually replaced by elective values in sound space, perceptual invariants selected via interaction with ingroup members; (5) achieving a desired phonological target results in enforced and reinforced via dopaminergic signaling, which instantiate encoding of combinations of motor sensory and auditory perceptual features.

Complex motor learning, underlying vocal learning, is contingent on sensory feedback. More broadly, basal ganglion function likely underlies learning through parsing successful from unsuccessful motor behavior, compared to desired outcomes . Basal ganglia, through being part of the neural dopaminergic circuitry, provide the necessary emphasis for mapping speech sounds, once achieved, to its corresponding place in orosensory space, facilitating repetition across continuous interaction. Neurologically, internally guided vocal explorative behavior and imitation are likely enabled by common ventral tegmental area-basal ganglion circuitry and guided via cortical-basal ganglion circuitry. Recent work has also suggested that the human laryngeal motor cortex, center for motor control of the larynx, may be modulated by dopamine via its being part of the vocal basal ganglia circuitry. Any achieved combinatory pattern thus subsequently becomes more easily repeatable through continuous reinstatement. A novel method for conceptualizing speech development, where emergent speech capacities are described as the cognitive mapping of coordinates in laryngeal-orosensory space, is described. Future directions are discussed.

Simmetry bias refers to the expectation that if exposed to two subsequent stimuli (A→B), humans also expect (B→A) to hold, which has been argued to be crucial for language development, in particular, for word learning, and possibly be important for language evolution. In non-human animals, it is often stated that symmetry bias does not exist. However, Lionello-DeNolf et al. (2021) claimed that symmetry bias was confirmed in approximately 30% of the non-human animals examined. It has been suggested that self- domestication, or becoming less aggressive and prosocial (Range et al, 2022), may be a preadaptation to language, and dogs have a long history of cooperation with humans and they developed such trains. In addition, dogs show similar contextual considerations to human infants, unlike trained wolves (Topál et al, 2009). In this preliminary study, we tested dogs on symmetry bias as a basis of word learning using behavior measures.

In the experiment, we first trained three dogs (poodles) to make associations between toys. Two kinds of toys were prepared: One that can be thrown (Toy A) and another that can be pulled (Toy B). For each toy, two significantly distinct sounds were corresponded. Sound A and Sound B (not the sounds of these toys) were played using a cellphone. In the training with Toy A, after the dog looked at the toy for 3 seconds, the experimenter played Sound A and simultaneously threw the toy. The dog fetched the toy and the experimenter praised the dog. This activity was repeated for 5 minutes. Then, another session with Toy B started. This totally 10-minutes training was done once a day for a month. An association test (MTS: matching-to-sample test) was done once a week. Two toys were placed in front of the dog, and either Sound A or Sound B was played. The dogʼs responses were recorded. After one of the dogs successfully passed the MTS test, a symmetry bias test was conducted. In the symmetry bias test, the toys and sounds were presented in a reverse order (i.e., Sound→ Toy). In the inconsistent condition, Sound A was played and only Toy B was placed in front of the dog. In the consistent condition, Sound A was played and only Toy A was similarly placed. All sessions were recorded on video and the dogʼs behavior was coded by frame-by- frame method.

The reaction time under the inconsistent condition was 1.6 sec, and that under the consistent condition was 1.1 sec. Thus, the dog responded more slowly to the toy in the inconsistent condition. The behavioral measurement also suggested that the dog seemed hesitant to take the toy that eventually took in the inconsistent condition, for example by looking around the toy rather than taking it. In the consistent condition, the dog went to the toy directly without hesitation. This result suggests that dogs may have symmetry bias. Then why dogs might have developed symmetry bias? We speculate that cooperation with humans who have naturally assumed symmetry bias might have promoted symmetry bias in dogs.