Publications

Abstract

We present a dataset of behavioural and fMRI observations acquired in the context of humans involved in multimodal referential communication. The dataset contains audio/video and motion-tracking recordings of face-to-face, task-based communicative interactions in Dutch, as well as behavioural and neural correlates of participants’ representations of dialogue referents. Seventy-one pairs of unacquainted participants performed two interleaved interactional tasks in which they described and located 16 novel geometrical objects (i.e., Fribbles) yielding spontaneous interactions of about one hour. We share high-quality video (from three cameras), audio (from head-mounted microphones), and motion-tracking (Kinect) data, as well as speech transcripts of the interactions. Before and after engaging in the face-to-face communicative interactions, participants’ individual representations of the 16 Fribbles were estimated. Behaviourally, participants provided a written description (one to three words) for each Fribble and positioned them along 29 independent conceptual dimensions (e.g., rounded, human, audible). Neurally, fMRI signal evoked by each Fribble was measured during a one-back working-memory task. To enable functional hyperalignment across participants, the dataset also includes fMRI measurements obtained during visual presentation of eight animated movies (35 minutes total). We present analyses for the various types of data demonstrating their quality and consistency with earlier research. Besides high-resolution multimodal interactional data, this dataset includes different correlates of communicative referents, obtained before and after face-to-face dialogue, allowing for novel investigations into the relation between communicative behaviours and the representational space shared by communicators. This unique combination of data can be used for research in neuroscience, psychology, linguistics, and beyond.

Abstract

In this increasingly data-rich world, visual recordings of human behavior are often unable to be shared due to concerns about privacy. Consequently, data sharing in fields such as behavioral science, multimodal communication, and human movement research is often limited. In addition, in legal and other non-scientific contexts, privacy-related concerns may preclude the sharing of video recordings and thus remove the rich multimodal context that humans recruit to communicate. Minimizing the risk of identity exposure while preserving critical behavioral information would maximize utility of public resources (e.g., research grants) and time invested in audio–visual​ research. Here we present an open-source computer vision tool that masks the identities of humans while maintaining rich information about communicative body movements. Furthermore, this masking tool can be easily applied to many videos, leveraging computational tools to augment the reproducibility and accessibility of behavioral research. The tool is designed for researchers and practitioners engaged in kinematic and affective research. Application areas include teaching/education, communication and human movement research, CCTV, and legal contexts.

Abstract

In many musical styles, vocalists manually gesture while they sing. Coupling between gesture kinematics and vocalization has been examined in speech contexts, but it is an open question how these couple in music making. We examine this in a corpus of South Indian, Karnatak vocal music that includes motion-capture data. Through peak magnitude analysis (linear mixed regression) and continuous time-series analyses (generalized additive modeling), we assessed whether vocal trajectories around peaks in vertical velocity, speed, or acceleration were coupling with changes in vocal acoustics (namely, F0 and amplitude). Kinematic coupling was stronger for F0 change versus amplitude, pointing to F0's musical significance. Acceleration was the most predictive for F0 change and had the most reliable magnitude coupling, showing a one-third power relation. That acceleration, rather than other kinematics, is maximally predictive for vocalization is interesting because acceleration entails force transfers onto the body. As a theoretical contribution, we argue that gesturing in musical contexts should be understood in relation to the physical connections between gesturing and vocal production that are brought into harmony with the vocalists’ (enculturated) performance goals. Gesture–vocal coupling should, therefore, be viewed as a neuro–bodily distributed aesthetic entanglement.

Abstract

Conversational turn taking in humans involves incredibly rapid responding. The timing mechanisms underpinning such responses have been heavily debated, including questions such as who is doing the timing. Similar to findings on rhythmic tapping to a metronome, we show that floor transfer offsets (FTOs) in telephone conversations are serially dependent, such that FTOs are lag-1 negatively autocorrelated. Finding this serial dependence on a turn-by-turn basis (lag-1) rather than on the basis of two or more turns, suggests a counter-adjustment mechanism operating at the level of the dyad in FTOs during telephone conversations, rather than a more individualistic self-adjustment within speakers. This finding, if replicated, has major implications for models describing turn taking, and confirms the joint, dyadic nature of human conversational dynamics. Future research is needed to see how pervasive serial dependencies in FTOs are, such as for example in richer communicative face-to-face contexts where visual signals affect conversational timing.

Abstract

Do communicative actions such as gestures fundamentally differ in their control mechanisms from other actions? Evidence for such fundamental differences comes from a classic gesture-speech coordination experiment performed with a person (IW) with deafferentation (McNeill, 2005). Although IW has lost both his primary source of information about body position (i.e., proprioception) and discriminative touch from the neck down, his gesture-speech coordination has been reported to be largely unaffected, even if his vision is blocked. This is surprising because, without vision, his object-directed actions almost completely break down. We examine the hypothesis that IW’s gesture-speech coordination is supported by the biomechanical effects of gesturing on head posture and speech. We find that when vision is blocked, there are micro-scale increases in gesture-speech timing variability, consistent with IW’s reported experience that gesturing is difficult without vision. Supporting the hypothesis that IW exploits biomechanical consequences of the act of gesturing, we find that: (1) gestures with larger physical impulses co-occur with greater head movement, (2) gesture-speech synchrony relates to larger gesture-concurrent head movements (i.e. for bimanual gestures), (3) when vision is blocked, gestures generate more physical impulse, and (4) moments of acoustic prominence couple more with peaks of physical impulse when vision is blocked. It can be concluded that IW’s gesturing ability is not based on a specialized language-based feedforward control as originally concluded from previous research, but is still dependent on a varied means of recurrent feedback from the body.

Abstract

Gestures during speaking are typically understood in a representational framework: they represent absent or distal states of affairs by means of pointing, resemblance, or symbolic replacement. However, humans also gesture along with the rhythm of speaking, which is amenable to a non-representational perspective. Such a perspective centers on the phenomenon of vocal-entangled gestures and builds on evidence showing that when an upper limb with a certain mass decelerates/accelerates sufficiently, it yields impulses on the body that cascade in various ways into the respiratory–vocal system. It entails a physical entanglement between body motions, respiration, and vocal activities. It is shown that vocal-entangled gestures are realized in infant vocal–motor babbling before any representational use of gesture develops. Similarly, an overview is given of vocal-entangled processes in non-human animals. They can frequently be found in rats, bats, birds, and a range of other species that developed even earlier in the phylogenetic tree. Thus, the origins of human gesture lie in biomechanics, emerging early in ontogeny and running deep in phylogeny.

Abstract

How does communicative efficiency shape language use? We approach this question by studying it at the level of the dyad, and in terms of multimodal utterances. We investigate whether and how people minimize their joint speech and gesture efforts in face-to-face interactions, using linguistic and kinematic analyses. We zoom in on other-initiated repair—a conversational microcosm where people coordinate their utterances to solve problems with perceiving or understanding. We find that efforts in the spoken and gestural modalities are wielded in parallel across repair turns of different types, and that people repair conversational problems in the most cost-efficient way possible, minimizing the joint multimodal effort for the dyad as a whole. These results are in line with the principle of least collaborative effort in speech and with the reduction of joint costs in non-linguistic joint actions. The results extend our understanding of those coefficiency principles by revealing that they pertain to multimodal utterance design.

Abstract

Most objects have well-defined affordances. Investigating perception of affordances of objects that were not created for a specific purpose would provide insight into how affordances are perceived. In addition, comparison of perception of affordances for such objects across different exploratory modalities (visual vs. haptic) would offer a strong test of the lawfulness of information about affordances (i.e., the invariance of such information over transformation). Along these lines, “feelies”— objects created by Gibson with no obvious function and unlike any common object—could shed light on the processes underlying affordance perception. This study showed that when observers reported potential uses for feelies, modality significantly influenced what kind of affordances were perceived. Specifically, visual exploration resulted in more noun labels (e.g., “toy”) than haptic exploration which resulted in more verb labels (i.e., “throw”). These results suggested that overlapping, but distinct classes of action possibilities are perceivable using vision and haptics. Semantic network analyses revealed that visual exploration resulted in object-oriented responses focused on object identification, whereas haptic exploration resulted in action-oriented responses. Cluster analyses confirmed these results. Affordance labels produced in the visual condition were more consistent, used fewer descriptors, were less diverse, but more novel than in the haptic condition.

Abstract

During silent problem solving, hand gestures arise that have no communicative intent. The role of such co-thought gestures in
cognition has been understudied in cognitive research as compared to co-speech gestures. We investigated whether gesticulation
during silent problem solving supported subsequent performance in a Tower of Hanoi problem-solving task, in relation
to visual working-memory capacity and task complexity. Seventy-six participants were assigned to either an instructed gesture
condition or a condition that allowed them to gesture, but without explicit instructions to do so. This resulted in three
gesture groups: (1) non-gesturing; (2) spontaneous gesturing; (3) instructed gesturing. In line with the embedded/extended
cognition perspective on gesture, gesturing benefited complex problem-solving performance for participants with a lower
visual working-memory capacity, but not for participants with a lower spatial working-memory capacity.

Abstract

Speakers often use gesture to demonstrate how to perform actions—for example, they might show how to open the top of a jar by making a twisting motion above the jar. Yet it is unclear whether listeners learn as much from seeing such gestures as they learn from seeing actions that physically change the position of objects (i.e., actually opening the jar). Here, we examined participants' implicit and explicit understanding about a series of movements that demonstrated how to move a set of objects. The movements were either shown with actions that physically relocated each object or with gestures that represented the relocation without touching the objects. Further, the end location that was indicated for each object covaried with whether the object was grasped with one or two hands. We found that memory for the end location of each object was better after seeing the physical relocation of the objects, that is, after seeing action, than after seeing gesture, regardless of whether speech was absent (Experiment 1) or present (Experiment 2). However, gesture and action built similar implicit understanding of how a particular handgrasp corresponded with a particular end location. Although gestures miss the benefit of showing the end state of objects that have been acted upon, the data show that gestures are as good as action in building knowledge of how to perform an action.

Abstract

We show that the human voice has complex acoustic qualities that are directly coupled to peripheral musculoskeletal tensioning of the body, such as subtle wrist movements. In this study, human vocalizers produced a steady-state vocalization while rhythmically moving the wrist or the arm at different tempos. Although listeners could only hear but not see the vocalizer, they were able to completely synchronize their own rhythmic wrist or arm movement with the movement of the vocalizer which they perceived in the voice acoustics. This study corroborates
recent evidence suggesting that the human voice is constrained by bodily tensioning affecting the respiratory-vocal system. The current results show that the human voice contains a bodily imprint that is directly informative for the interpersonal perception of another’s dynamic physical states.

Abstract

Co-speech gestures have been proposed to strengthen sensorimotor knowledge related to objects’ weight and manipulability.
This pre-registered study (https ://www.osf.io/9uh6q /) was designed to explore how gestures affect memory for sensorimotor
information through the application of the visual-haptic size-weight illusion (i.e., objects weigh the same, but are experienced
as different in weight). With this paradigm, a discrepancy can be induced between participants’ conscious illusory
perception of objects’ weight and their implicit sensorimotor knowledge (i.e., veridical motor coordination). Depending on
whether gestures reflect and strengthen either of these types of knowledge, gestures may respectively decrease or increase
the magnitude of the size-weight illusion. Participants (N = 159) practiced a problem-solving task with small and large
objects that were designed to induce a size-weight illusion, and then explained the task with or without co-speech gesture
or completed a control task. Afterwards, participants judged the heaviness of objects from memory and then while holding
them. Confirmatory analyses revealed an inverted size-weight illusion based on heaviness judgments from memory and we
found gesturing did not affect judgments. However, exploratory analyses showed reliable correlations between participants’
heaviness judgments from memory and (a) the number of gestures produced that simulated actions, and (b) the kinematics of
the lifting phases of those gestures. These findings suggest that gestures emerge as sensorimotor imaginings that are governed
by the agent’s conscious renderings about the actions they describe, rather than implicit motor routines.

Abstract

Expressive moments in communicative hand gestures often align with emphatic stress in speech. It has recently been found that acoustic markers of emphatic stress arise naturally during steady-state phonation when upper-limb movements impart physical impulses on the body, most likely affecting acoustics via respiratory activity. In this confirmatory study, participants (N = 29) repeatedly uttered consonant-vowel (/pa/) mono-syllables while moving in particular phase relations with speech, or not moving the upper limbs. This study shows that respiration-related activity is affected by (especially high-impulse) gesturing when vocalizations occur near peaks in physical impulse. This study further shows that gesture-induced moments of bodily impulses increase the amplitude envelope of speech, while not similarly affecting the Fundamental Frequency (F0). Finally, tight relations between respiration-related activity and vocalization were observed, even in the absence of movement, but even more so when upper-limb movement is present. The current findings expand a developing line of research showing that speech is modulated by functional biomechanical linkages between hand gestures and the respiratory system. This identification of gesture-speech biomechanics promises to provide an alternative phylogenetic, ontogenetic, and mechanistic explanatory route of why communicative upper limb movements co-occur with speech in humans.
ACKNOWLEDGMENTS

Abstract

We introduce applications of established methods in time-series and network
analysis that we jointly apply here for the kinematic study of gesture
ensembles. We define a gesture ensemble as the set of gestures produced
during discourse by a single person or a group of persons. Here we are
interested in how gestures kinematically relate to one another. We use
a bivariate time-series analysis called dynamic time warping to assess how
similar each gesture is to other gestures in the ensemble in terms of their
velocity profiles (as well as studying multivariate cases with gesture velocity
and speech amplitude envelope profiles). By relating each gesture event to
all other gesture events produced in the ensemble, we obtain a weighted
matrix that essentially represents a network of similarity relationships. We
can therefore apply network analysis that can gauge, for example, how
diverse or coherent certain gestures are with respect to the gesture ensemble.
We believe these analyses promise to be of great value for gesture
studies, as we can come to understand how low-level gesture features
(kinematics of gesture) relate to the higher-order organizational structures
present at the level of discourse.

Abstract

The phenomenon of gesture–speech synchrony involves tight coupling of prosodic contrasts in gesture
movement (e.g., peak velocity) and speech (e.g., peaks in fundamental frequency; F0). Gesture–speech
synchrony has been understood as completely governed by sophisticated neural-cognitive mechanisms.
However, gesture–speech synchrony may have its original basis in the resonating forces that travel through the
body. In the current preregistered study, movements with high physical impact affected phonation in line with
gesture–speech synchrony as observed in natural contexts. Rhythmic beating of the arms entrained phonation
acoustics (F0 and the amplitude envelope). Such effects were absent for a condition with low-impetus
movements (wrist movements) and a condition without movement. Further, movement–phonation synchrony
was more pronounced when participants were standing as opposed to sitting, indicating a mediating role for
postural stability. We conclude that gesture–speech synchrony has a biomechanical basis, which will have
implications for our cognitive, ontogenetic, and phylogenetic understanding of multimodal language.

Abstract

There is increasing evidence that hand gestures and speech synchronize their activity on multiple dimensions and timescales. For example, gesture’s kinematic peaks (e.g., maximum speed) are coupled with prosodic markers in speech. Such coupling operates on very short timescales at the level of syllables (200 ms), and therefore requires high-resolution measurement of gesture kinematics and speech acoustics. High-resolution speech analysis is common for gesture studies, given that field’s classic ties with (psycho)linguistics. However, the field has lagged behind in the objective study of gesture kinematics (e.g., as compared to research on instrumental action). Often kinematic peaks in gesture are measured by eye, where a “moment of maximum effort” is determined by several raters. In the present article, we provide a tutorial on more efficient methods to quantify the temporal properties of gesture kinematics, in which we focus on common challenges and possible solutions that come with the complexities of studying multimodal language. We further introduce and compare, using an actual gesture dataset (392 gesture events), the performance of two video-based motion-tracking methods (deep learning vs. pixel change) against a high-performance wired motion-tracking system (Polhemus Liberty). We show that the videography methods perform well in the temporal estimation of kinematic peaks, and thus provide a cheap alternative to expensive motion-tracking systems. We hope that the present article incites gesture researchers to embark on the widespread objective study of gesture kinematics and their relation to speech.