Types of accommodation
Heath (2014, 2015) proposes that at least six different types of accommodation can occur when considering multiple phonetic features interacting simultaneously: (a) convergence: increase of similarity regarding the speech of the interlocutor4; (b) divergence: increase of dissimilarity regarding the speech of the interlocutor; (c) orthogonal accommodation: accommodation that does not increase the similarity or the dissimilarity regarding the model. That is to say, “changing one’s own speech in response to an interlocutor’s speech, but in a manner not reflected in that interlocutor’s speech. An example would be speaking in a whisper in response to a statement about a sleeping baby” (Heath, 2014, p. 122); (d) antagonistic accommodation: increase of similarity regarding one specific factor of the interlocutor’s speech, while increasing the dissimilarity with respect to another factor; (e) hyperconvergence : increase of similarity until matching the speech of the interlocutor, and then increase of dissimilarity in the opposite direction; and (f) null accommodation: lack of accommodation.
De Looze and Rauzy (2011, p. 1393), in turn, propose the existence of (a) anti-similarity, which would be divided in (a1) anti-proximity (anti-synchrony in the authors’ terms), “the tendency for speakers to differentiate their speech from the other’s, resulting in mirror or anti-correlated patterns,” and (a2) divergence, “[speakers’] tendency to move apart towards different directions.” In addition, (b) no-similarity would be a situation in which speakers do not exhibit proximity, anti-proximity, convergence, or divergence. As suggested by De Looze and Rauzy (2011), the combination of these phenomena would lead to seven different states (indicated here using our own terminology): three states of similarity (proximity, convergence, or both of them), three states of anti-similarity (anti-proximity, divergence, or both of them), and one state of no similarity (no proximity and no convergence).
It is worth noting that synchronization / convergence has been treated as the default form of accommodation during conversations. Nonetheless, the increase of similarity between linguistic and paralinguistic behaviors is not the only possible outcome of an 4 Convergence between two speakers can be both unidirectional (A → B), or (B → A), as well as bidirectional (A ↔ B) (Kousidis et al., 2009).
interaction. As mentioned above, an increasing difference between speakers’ speech features and associated behaviors (divergence) may also occur (Heath, 2014, 2015).
Divergence between interlocutors may be due to different reasons, such as an infrequent behavior that might not provide enough exposure to allow synchronization (e.g. to make an “O” shape with the mouth) (Louwerse et al., 2012). Not converging with an interlocutor may also be understood as showing creativity in linguistic choices: an attractive quality that would lead to a positive impression of the speaker (Schoot et al., 2016).
The concept of speech complementarity is considered by Muir, Joinson, Cotterill and Dewdney (2017) as a possible explanation of the divergence in linguistic style between interlocutors observed in their study (which is commented in Section 2.4.5.). According to this concept, some divergent communicative behaviors have the function of conveying and reinforcing social roles. This would be especially true in contexts such as organizational hierarchies, which often present highly expectations about appropriate behavior at the different levels of grading. In this scenario, individuals would rely on speech complementarity to maintain and reinforce hierarchical roles.
With respect to phonological accommodation, as believed by Heath (2015), physiological or learned restrictions on articulatory movements imply that convergence along incompatible phonetic features (e.g. VOT and stop closure duration), measured under experimental conditions, is not to be expected. It should be expected, instead, divergence in at least one of the measured features (an experiment supporting this claim is discussed in Section 2.4.1.).
Finally, according to Heath (2014, 2015), speech modifications due to divergence between interlocutors do not tend to persist beyond the interaction in which they are realized, thus it is unlikely that divergent behaviors can generate stable language variations.
Development of accommodation
Phylogenetic development of accommodation
Human speech implies an inherent rhythmic coordination between the articulatory, respiratory, and phonatory systems. This type of vocal and bodily coordination with an external steady beat (speech) is a rare behavior in other animals, including non-human primates. Moreover, the ability of two or more organisms to engage in group behavioral coordination with a repeating beat, as is the case of conversations, seems to be unique for humans. Nonetheless, such coordination ability can also be found at some extent in species that are not closely related to men, including frogs, crickets, and ants. These animals take advantage of this behavioral coordination for mating and defending purposes (Merker, Madison & Eckerdal, 2009).
In this respect, Merker et al. (2009) propose that the ability to coordinate movements or vocalizations, or both, with a shared, repeating interval of time, would have evolved from specific primate behaviors, such as the so-called carnival display (i.e. groups of chimpanzees engaged in a chaotic voice and movement exhibition; stomping, running, and slapping trees, without any explicit indication of inter-individual coordination). In this scenario, the human ability to coordinate in pairs, or in groups, with a steady beat source of sound, is seen as a refinement of an ancient connection between calls and movements already present among the human hominoid ancestors. This ability would have evolved for purposes of mate attraction, by enabling the voice coordination needed for enhancing the signal directed to distant females.
In terms of empirical research, although the existence of behavioral synchronization between non-human species has been hardly investigated (Duranton & Gaunet, 2016), there are some studies of accommodation processes between non-human animals that include bird flocks, monkeys, and bats.
Several species of non-human primates, for instance, modify the structure of their calls in response to environmental acoustic signals and conspecifics’ vocalizations, which may be considered as a process of vocal accommodation with respect to spatial location and social context (Barón, 2016). Furthermore, long-term vocal accommodation in non-human primates has been reported during pair and group formation, apparently aimed to reinforce dyadic bonds and group identity (Ruch, Zürcher & Barkart, 2017).
Regarding bats, it has been found that the first vocalizations of the Egyptian fruit bat pups consist in isolation calls produced when the pup is left alone in the roost, or when he fears that he may be separated from his mother (Prat, Taub & Yovel, 2015). These calls are innate, appear at the first day after birth, and gradually converge, in terms of resemblance of acoustic features, toward adult-like calls during the first months of life. During this period, the highly diverse repertoire of pups’ vocalizations disappears and becomes normalized (adult-like) within a month. This process can be compared to the crystallization stage in birds’ singing, and with babbling and phonemic reduction in production and comprehension (respectively) in infants.
Regarding birds’ songs, a critical acquisition period defines the time in which melodies may be learned. This sensitive period is divided in two phases: sensory learning (listening) and sensory-motor learning (listening-repeating) (Doupe & Kuhl, 1999). During sensory-motor learning, a subsong is produced by the young birds. These subsongs are generic among individuals, yet comprising variations, in a similar way of that of infants’ babbling and mice ultrasonic vocalizations (Arriaga, Zhou & Jarvis, 2012). Subsongs eventually become plastic songs, which vary greatly between implementations, while gradually converging toward the song of the bird’s tutor (an adult bird) in terms of resemblance of acoustic features. Plastic songs remain until the bird crystallizes them into stable mature songs, and from then on new songs cannot be learned (Doupe & Kuhl, 1999).
In terms of functionality, behavioral coordination has an adaptive value for clusters of animals, including decreasing the pressure of predation on offspring and increasing the effectiveness of protection against predators (Duranton & Gaunet, 2016). Rapidly matching acoustic signals, for instance, allows the vocalizer to address individual conspecifics, in a context where a signal can be directed at a multitude of listeners5.
Furthermore, based on functional parallels between humans and other species, Ruch et al. (2017) suggest that the communicative function of vocal accommodation to signal social closeness or distance to a partner or a group, along with some level of vocal control, evolved before the emergence of language rather than being the result of it. From this 5 Interestingly, in the animal kingdom the timing of a response is a key factor in vocal matching. Whereas a prolonged interval between emissions may not be perceived as a response to the first signal, a hasty reply may be perceived as a sign of aggression. Overlapping of the signal between individuals, however, is not a common occurrence, and sometimes serves an affiliative purpose in birds‘ duet signing (King et al., 2014). standpoint, vocal accommodation is seen as a pre-adaptation that would have paved the way for language evolution.
On the other hand, the evolution of an imitation ability represents a major precursor to the evolution of language and one of the main steps in the evolution beyond the great ape level (MacNeilage, 1998). However, in the words of Fitch (2010, p. 163): “the capacity of human infants and children … to imitate motor actions (as well as vocalizations) remains unparalleled in its richness, despite clear homologs in ape behavior.”
In any case, beyond homologs in great apes’ imitation behaviors, it has been proposed recently that the capacity for interactional synchrony is shared between humans, chimpanzees, bonobos, and macaques (Yu, Hattori, Yamamoto & Tomonaga, 2018). In line with this statement, and after a detailed analysis of vocal accommodation in non-human primates, Ruch et al. (2017) conclude:
There are surprisingly strong parallels in the function of vocal accommodation in humans and primates, which are consistent with the optimization of signal transmission and CAT [communication accommodation theory] and suggest an early phylogenetic origin of these functions. These results strongly suggest that this social function of accommodation already existed prior to the evolution of language. (Ruch et al., 2017, p. 13).
Ontogenetic development of accommodation
Behavioral coordination between infants and their caregivers allows them to create and maintain a strongly attached relationship that is essential for the development of the child (Duranton & Gaunet, 2016) (An overview of this topic, including infant-infant early interactions, can be found in the third chapter of Inui, 2018). It has been proposed that this process relies on brain mechanisms operating by means of coupling coordinated rhythmic oscillators (Trevarthen, 1998). In the words of Beebe, Knoblauch, Rustin and Sorter (2003, pp. 818-819): “the pacemakers of motor systems are already coupled at birth, and all movements are played out in one time frame, ‘intersynchronized’…. This coupling provides a physiological basis for endogenous coordination of perception and action…” Moreover, “the biological basis for the infant’s capacity to partake in synchronous social dialogue is provided by the organization of physiological oscillators during the neonatal period, such as the biological clock and heart rhythms…” (Feldman, Mayes & Swain, 2005, p. 24).
Additionally, Feldman et al. (2005) argue that parent-infant coordination has an important role in the development of the child’s brain and predicts her or his cognitive skills and behavioral adaptation in later years. Interestingly, Feldman et al. (2005) also present evidence indicating that the degree of parent-infant coordination tends to decrease in cases of maternal depression, prematurity, or multiple births.
In the following lines we sketch a chronological non-exhaustive list of developmental stages of early infancy related to capacities that underpin the process of accommodation, including imitation, coordination, and rhythmicity:
x A seemingly universal proto-language is created between mother and infant during their early interactions. Prosodic modulations play a key role during these interactions to the point that even deaf mothers initially vocalize to their deaf infants, although neither of them can hear the sound (MacNeilage, 1998).
x As early as 42 minutes after birth, newborns exhibit a rudimentary form of deferred imitation of facial gestures (Beebe et al., 2003). According to Beebe et al. (2003), such imitation capacity implies the existence of multimodal pre-symbolic representations that are stored and compared with the own motor planning to match the gestures observed and produced. These multimodal representations include spatial, temporal, and visual aspects related to actions, which serve to remember and identify different persons. Progressively, the multimodal representations would become more stable, permitting thus longer periods of time between perceiving and imitating gestures.
x Already within the first hours of life, newborns can imitate tongue and lips protrusion, mouth opening, smiles, and an expression of surprise. Tongue protrusion can be imitated after two or three minutes after have seen the model (Beebe et al., 2003).
x Neonates (from 12 hours to 2 days old) are able to detect the rhythm of adult speech and synchronize their movements with it (Condon & Sander, 1974; for a criticism of the visual scoring approach, applied in this study, see Section 2.4.4.).
x Two- to five-day-old infants’ cries exhibit tonal contours similar to those of their mother tongue (Mampe, Friederici, Christophe & Wermke, 2009).
x Since their first weeks of life, infants are able to perceive transmodal correspondences between what they see on the faces of other persons and the proprioceptive sensations of their own face (Beebe et al., 2003). Moreover, few weeks after being born, infants are already capable of maintain direct face-to-face interactions, coordinating vocal, oral, and gestural expressions (Beebe et al., 2003).
x Within the first eight weeks of life, infants are able to integrate speech characteristics highlighted by their caregiver into their own vocal production (Van Puyvelde, Loots, Gillisjans, Pattyn & Quintana, 2015).
x During the first months of life, infants exhibit diverse repetitive rhythmic movements, including kicking, rocking, and bouncing. In terms of articulatory and phonatory regularities, babbling is another one of these repetitive rhythmic behaviors (MacNeilage, 1998). Also during the first months of life, infants acquire diverse perceptual capacities that allow them to communicate with others, including binocular vision, selective attention, memory of contexts for object recognition, and discrimination of face patterns (Beebe et al., 2003 and references therein).
x The capacity to imitate sounds has been reported as early as two to six months of age, while other reports suggest that this particular ability does not develop entirely until the second year of life (Nguyen & Delvaux, 2015 and references therein).
x At about three months of age, infants are able to produce speech-like, as well as non-speech-like, vocal sounds (Van Puyvelde et al., 2015). Also, infants begin to open and close their mouths and move their tongues while paying attention to the adult’s face and voice during episodes of interaction that involve eye-to-eye contact, and sometimes, infants’ voicing (Bloom, 1998). It has also been reported that during mutual vocalizations, mothers and their three-month-old infants alter the pitch ratios and timing patterns of their utterances in such a way that the dyadic vocal exchanges become tonally synchronized (Van Puyvelde et al., 2015). Additionally, during the third month of life, infants begin to participate in synchronous social interactions, in which they learn to take turns in vocal exchanges and match their partner’s gaze directions and facial expressions. “These early face-to-face interactions between parents and infants are composed of microlevel behavioral units that follow dyad-specific rhythmic patterns, and infants at that stage can anticipate the partner’s rhythms and coordinate their behavior accordingly” (Feldman et al., 2005, p. 24).
Table of contents :
2.2. Types of accommodation
2.3. Development of accommodation
2.3.1. Phylogenetic development of accommodation
2.3.2. Ontogenetic development of accommodation
2.4. Modalities of accommodation
2.4.1. Phonetic accommodation
2.4.2. Syntactic accommodation
2.4.3. Lexical accommodation
2.4.4. Rhythmic (and turn-taking) accommodation
2.4.5. Linguistic and speaking style accommodation
2.4.6. Gestural and postural accommodation
2.5. Characteristics of accommodation
2.5.2. Automaticity and degree of awareness
2.5.3. Role, gender, and social biases
2.5.4. Task difficulty and timing
2.6. Theoretical frameworks of accommodation
2.6.1. Communication accommodation theory (CAT)
2.6.2. Interactive alignment model (IAM)
3. Speech rhythm
3.1.1. The isochrony hypothesis
3.1.2. Alternative views of speech rhythm
3.2. The rhythm of Spanish
3.2.1. General facts and stress patterns
3.2.2. Phonological phrasing
3.2.3. Rhythmic classification of Spanish
3.2.4. Resyllabification and sirrema
3.2.5. (Rhythmic) Secondary stress
3.2.6. Rhythmicity and rhythmic alternation principle
4.2. Materials and methods
4.2.1. Experiment 1: Acoustic evaluation
4.2.2. Experiment 2: Perceptual evaluation
4.3. Data analysis
Preparation of participants’ recordings – Determination of dependent variables –Statistical approach
4.4.1. Experiment 1: Acoustic evaluation
4.4.2. Experiment 2: Perceptual evaluation
5. Discussion and conclusions