Verónica C. Ramenzoni

Tuning in to another person's action capabilities: perceiving maximal jumping-reach height from walking kinematics.

Three experiments investigated the ability to perceive the maximum height to which another actor could jump to reach an object. Experiment 1 determined the accuracy of estimates for another actors maximal reach-with-jump height and compared these estimates to estimates of the actors standing maximal reaching height and to estimates of the perceivers own maximal reaching and reach-with-jump height. Perception of another actors maximum reach-with-jump height was less accurate than the other estimates, but still accurate to within 8% error. The actors reach-with-jump height was modified in Experiment 2 by attaching weights around the actors ankles. Perceivers, who were explicitly aware of the manipulation, adjusted their maximum reach-with-jump estimates for the actor accordingly. In Experiment 3, perceivers were not explicitly aware of the weight manipulation, but provided significantly lower maximum reach-with-jump estimates after watching the actor walk while wearing the weights compared to estimates obtained after watching the actor walk while not wearing the weights. The results suggest that the actors walking pattern was informative about the actors capacity to produce a different action, jumping to reach an object.

Joint action in a cooperative precision task: nested processes of intrapersonal and interpersonal coordination

The authors determined the effects of changes in task demands on interpersonal and intrapersonal coordination. Participants performed a joint task in which one participant held a stick to which a circle was attached at the top (holding role), while the other held a pointer through the circle without touching its borders (pointing role). Experiment 1 investigated whether interpersonal and intrapersonal coordination varied depending on task difficulty. Results showed that interpersonal and intrapersonal coordination increased in degree and stability with increments in task difficulty. Experiment 2 explored the effects of individual constraints by increasing the balance demands of the task (one or both members of the pair stood in a less stable tandem stance). Results showed that interpersonal coordination increased in degree and stability as joint task demands increased and that coupling strength varied depending on joint and individual task constraints. In all, results suggest that interpersonal and intrapersonal coordination are affected by the nature of the task performed and the constraints it places on joint and individual performance.

Carrying the height of the world on your ankles: Encumbering observers reduces estimates of how high an actor can jump

The authors investigated how changes in action capabilities affect estimation of affordances for another actor. Observers estimated maximum jumping-reach height for themselves and another actor. Half of the observers wore ankle weights that reduced their jumping ability. The ankle weights reduced estimates of maximum jumping-reach height that observers made for themselves and for the other actor, but only after observers had the opportunity to walk while wearing the weights. Changes in estimates closely matched changes in actual jumping-reach ability. Results confirm and extend recent investigations that indicate that perception of the spatial layout of surfaces in the environment is scaled to an observers capacity to act, and they link that approach to another embodied cognition perspective that posits a link between ones own action capabilities and perception of the actions of other agents.

Perceiving action boundaries: Learning effects in perceiving maximum jumping-reach affordances

Coordinating with another person requires that one can perceive what the other is capable of doing. This ability often benefits from opportunities to practice and learn. Two experiments were conducted in which we investigated perceptual learning in the context of perceiving the maximum height to which an actor could jump to reach an object. Those estimates were compared with estimates that perceivers made for themselves. In Experiment 1, participants initially underestimated the maximum jumping-reach height both for themselves and for the actor. Over time, without explicit feedback, the participants were able to improve estimates of their own maximum jumping-reach height, but estimates for the actor did not improve. In Experiment 2, participants observed the actor perform either an action related but nonidentical to jumping (lifting a weight by squatting) or a nonrelated activity (rotating the torso). The participants who observed the actor perform the related action were able to improve the accuracy of their perceptual reports for the actor’s maximum jumping-reach height, but the participants who watched the actor perform the nonrelated task were unable to do so. The results indicate some degree of independence between perceived affordances for the self and others, suggesting that affordance judgments are not entirely dependent on or determined by characteristics of the perceiver.

Interpersonal and intrapersonal coordinative modes for joint and single task performance

In recent years, research in the field of social interactions has focused on the exploration of the coordinative structures that substantiate joint task performance. The current project explores whether interpersonal coordination during joint task performance gives rise to a joint coordinative structure across individuals, and whether such coordinative structures are affected by task demands. Principal component analysis (PCA) is used to identify relevant interpersonal and intrapersonal coordinative modes for the single and joint performance of a supra-postural task, which varied along its precision and role demands. In addition, cross-recurrence quantification analysis (CRQA) was combined with PCA in order to quantify the degree and stability of interpersonal coordination across intrapersonal coordinative modes. Results indicate that the composition and number of coordinative modes varied for joint compared to single performance, and that interpersonal coordination across the first coordinative mode increased in degree and stability for joint compared to single performance. Overall, these findings indicate that joint coordinative structures are affected by the nature of the task performed and the constraints it places on joint and single performance.

Development of interpersonal coordination between peers during a drumming task

During social interaction, the behavior of interacting partners becomes coordinated. Although interpersonal coordination is well-studied in adults, relatively little is known about its development. In this project we explored how 2-, 3-, and 4-year-old children spontaneously coordinated their drumming with a peer. Results showed that all children adapted their drumming to their partners drumming by starting and stopping their drumming in a coordinated fashion, but only 4-year-olds adapted the rhythmic structure of their drumming to their partners drumming. In all age groups, children showed similarly stable drumming. Typically, it was 1 of the 2 children who initiated drumming throughout the session. The results of this study offer new insights into the development of interpersonal coordination abilities in early childhood.

Structural differences between open and direct communication in an online community

Most research of online communication focuses on modes of communication that are either open (like forums, bulletin boards, Twitter, etc.) or direct (like e-mails). In this work, we study a dataset that has both types of communication channels. We relate our findings to theories of social organization and human dynamics. The data comprises 36,492 users of a movie discussion community. Our results show that there are differences in the way users communicate in the two channels that are reflected in the shape of degree- and interevent time distributions. The open communication that is designed to facilitate conversations with any member shows a broader degree distribution and more of the triangles in the network are primarily formed in this mode of communication. The direct channel is presumably preferred by closer communication and the response time in dialogs is shorter. On a more coarse-grained level, there are common patterns in the two networks. The differences and overlaps between communication networks, thus, provide a unique window into how social and structural aspects of communication establish and evolve.

Scaling up perception-action links: Evidence from synchronization with individual and joint action.

How do we map joint actions we participate in onto joint actions we observe others performing, such as when a couple dancing tango observes another couple dancing tango? We investigated this question using a task in which participants were instructed to perform individual or joint movements in synchrony with individual or joint movements observed on a computer screen. The observed movements started slowly and then continuously increased in tempo (from 1.75 Hz to 3 Hz). The results showed that, with regard to spatial parameters, joint performance was more accurate when observing joint action than when observing individual action (Experiments 1, 1a, and 1b). Individual performance was more accurate when observing individual action than when observing joint action (Experiments 3 and 4). There were no systematic differences with regard to timing parameters. These results suggest that mechanisms of temporal coordination may be less susceptible to differences between individual and joint action than mechanisms of spatial matching.

Emergence of collective memories.

Background We understand the dynamics of the world around us as by associating pairs of events, where one event has some influence on the other. These pairs of events can be aggregated into a web of memories representing our understanding of an episode of history. The events and the associations between them need not be directly experienced—they can also be acquired by communication. In this paper we take a network approach to study the dynamics of memories of history. Methodology/Principal Findings First we investigate the network structure of a data set consisting of reported events by several individuals and how associations connect them. We focus our measurement on degree distributions, degree correlations, cycles (which represent inconsistencies as they would break the time ordering) and community structure. We proceed to model effects of communication using an agent-based model. We investigate the conditions for the memory webs of different individuals to converge to collective memories, how groups where the individuals have similar memories (but different from other groups) can form. Conclusions/Significance Our work outlines how the cognitive representation of memories and social structure can co-evolve as a contagious process. We generate some testable hypotheses including that the number of groups is limited as a function of the total population size.

Synchronous Imitation of Continuous Action Sequences: The Role of Spatial and Topological Mapping

What are the mapping mechanisms that enable people to synchronously imitate continuous action sequences observed in others? We investigated this question in 4 experiments that used a tapping task where participants synchronously performed alternating bimanual hand movements with a model presented in an egocentric or allocentric orientation. Their task was to tap in synchrony, with each hand matching the movements of the ipsilateral model hand as closely as possible. The results show that automatic establishment of topological mappings, where the performers hand is mapped onto the models anatomically matching hand even if the 2 are spatially misaligned, can interfere with maintaining spatial mappings (Experiments 1 and 2). The interference was particularly strong in musicians who have expertise in establishing topological mappings in continuous performance (Experiment 4). Adopting an unusual body posture greatly interfered with establishing spatial as well as topological mappings (Experiment 3). Together, the results suggest that synchronous imitation of continuous action sequences depends on flexible predictive models that simultaneously apply spatial and topological mapping constraints to enable an actor to act in synchrony with observed action sequences.