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Séminaire du département Parole et Cognition du 25/11/2021 à 13h30

 

Signalling and Inferring Cooperative Urge Through Speech Rhythm

Intervenant : Mikahil Ordin, Basque Center on Cognition, Brain and Language

Lieu : B314

 

Résumé :

Patterns of speech rhythm in vocalization of animals (Rek & Osiejus, 2013) and in human speech (Pickering & Garrod, 2004) are correlated with the degree of the cooperative urge of the interacting agents and their mutual goodwill. However, there is little evidence whether the third-party observer is able to make pragmatic inferences regarding the cooperative behavior of the interacting agents or their hostility. We set up a series of studies to understand whether humans can map rhythmic patterns in interlocutors’ speech onto of pro-sociality and cooperative inclinations. 

For the analytical purposes, we consider rhythm at two levels: pulse (salient acoustic events, which may recur at regular or irregular intervals) and meter (hierarchical structuring of pulses into groups based on their relative salience). 

In the first series of experiments, we explored whether regularity in rhythm at the level of pulse (exp.1) and at the level of meter (exp.2) is perceived as a signal of cooperation and social bonding between the interlocutors. We found that regular pulse is indeed mapped the social bonding and cooperative urge, however, regularity at the level of meter is not associated with perceived pro-sociality and cooperation between interlocutors. We suggest that pulse isochrony allows better interpersonal motor and vocal coordination via motor coordination with the acoustic signal emitted by a different individual, which strengthens social bonding and promotes pro-social behavior. 

Additionally, we analyzed whether humans are aware of the pragmatic inferences they are making based on patterns of speech rhythm. Analysis of awareness indicators show that participants are more aware that isochrony at the level of pulse signals cooperation and social bonding. Awareness of one’s abilities is reflected in a feeling of confidence reported on each particular decision (Maniscalco, B. & Lau, 2012). Higher awareness enables assigning higher confidence ratings to correct responses than to incorrect responses, and consequently assign more or less credit to different information sources (in this case, particular rhythmic patterns), thus calibrating the behavior accordingly. Being aware of one’s decisions regarding the mental state (i.e., social bonding and cooperative inclinations within a group under observation) promotes development of intentionality and theory of mind, which is beneficial for the individuals’ fitness because the ability to understand the intentions of others allows active manipulation of their behavior and dynamically adjust one’s behavior through selective attention to the relevant properties of the communicative signal during language evolution (Dunbar, 2004). 

Isochrony is vocalizations may signal cooperative urge by facilitating social entrainment, which is the entrainment of behavior, including verbal behavior, to the signal emitted by a different conspecific individual (Phillips-Silver et al., 2010). In social entrainment, mechanisms of rhythmic cognition and synchronization of the motor output with the input signal are activated by the cues from the social environment and allow coordination of movements and vocalizations, including speech production, and even entrainment of neural oscillations (Bowling et al., 2013; Stephens et al., 2010). This further promotes social bonding (Haidt et al., 2008; Kirschner & Tomasello, 2009), and may signal, to the third-party observer, that the communicating individuals are socially affiliated. We tested this hypothesis in two further experiments, exploring whether rhythmic entrainment is speech of interacting agents will be perceived as a cue to the cooperative incination of the the individuals. The results suggest that rhythm convergence can be a marker of social cooperation at the level of pulse, but not at the level of meter. The mapping of rhythmic convergence onto social affiliation or opposition is important at the early stages of language acquisition. The evolutionary origin of this faculty is possibly the need to transmit and perceive coalition information in social groups of human ancestors. The mapping of vocal rhythm convergence onto social affiliation is important for the development of social cognition and for language acquisition in ontogenesis, and probably was an important facilitating factor for speech emergence in phylogenesis.

Below, we also present a figure showing how rhythmic isichrony in vocal signalling and entrainment of rhythmic patterns in vocalizations between individuals could have contributed to the emergence of speech faculty.


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