Kayhan Özcimder

Perceptual modalities guiding bat flight in a native habitat

Flying animals accomplish high-speed navigation through fields of obstacles using a suite of sensory modalities that blend spatial memory with input from vision, tactile sensing, and, in the case of most bats and some other animals, echolocation. Although a good deal of previous research has been focused on the role of individual modes of sensing in animal locomotion, our understanding of sensory integration and the interplay among modalities is still meager. To understand how bats integrate sensory input from echolocation, vision, and spatial memory, we conducted an experiment in which bats flying in their natural habitat were challenged over the course of several evening emergences with a novel obstacle placed in their flight path. Our analysis of reconstructed flight data suggests that vision, echolocation, and spatial memory together with the possible exercise of an ability in using predictive navigation are mutually reinforcing aspects of a composite perceptual system that guides flight. Together with the recent development in robotics, our paper points to the possible interpretation that while each stream of sensory information plays an important role in bat navigation, it is the emergent effects of combining modalities that enable bats to fly through complex spaces.

Investigating group behavior in dance: an evolutionary dynamics approach

We investigate group behavior in dance using an evolutionary dynamic model. Our approach is motivated by observations of nineteen dancers during a performance in which they choose a sequence of dance movements from a finite set of allowable movement modules as they perform. Results show evidence that subgroups of dancers performing the same movement module with greater representation are aware of their dominance, which in turn influences their switching rates between modules. We introduce the notion of awareness of dominance into the well-studied framework of replicator-mutator dynamics, where modules are represented as strategies. By letting awareness of dominance tune mutation strength, we demonstrate its influence in the evolution of strategies. The tuning yields a feedback controlled bifurcation in the model dynamics, which predicts persistence of dominant strategies as observed in the behavior of the dance group.

Dancing Robots: The Control Theory of Communication Through Movement

This chapter summarizes work to understand various aspects of the communication that occurs through the movements of partners in a dance. The first part of the paper adopts the terminology of motion description languages and deconstructs an elementary form of the well-known popular dance, salsa, in terms of four motion primitives (dance steps). These motion primitives can be specified entirely by the motions of the dancer’s feet, and hence the motions can be effectively carried out by simple unicycle-like mobile robots. We describe an experiment in which ten performances by an actual pair of dancers are evaluated by judges and then compared in terms of several complexity metrics. An energy metric is also defined. Values of this metric are obtained by summing up the lengths of motion segments executed by wheeled robots replicating the movements of the human dancers in each of ten dance performances. Of all the metrics that are considered in this experiment, energy is the most closely correlated with the human judges assessments of performance quality. The second part of the paper discusses an enhanced form of (intermediate level) salsa in which upper body motions play a role in the steps of the dance. In this version, it is stipulated that the dancers must remain in physical contact by holding hands. The number of motion primitives is increased to eleven, and the requirement that the dancers’ hands must remain linked imposes constraints on the structure of the dance sequences. These constraints are discussed using simple ideas from topological knot theory. Using a natural Markov model to generate possible dance sequences, it is shown that because the topological constraints enforce syntactic constraints on the motion transitions, the entropy rate of the intermediate level salsa is smaller than that of the beginner level salsa. The chapter concludes with a brief discussion of the challenges and possible approaches to creating robotic movement that will be perceived as having artistic merit.

Perception and Steering Control in Paired Bat Flight

Animals within groups need to coordinate their reactions to perceived environmental features and to each other in order to safely move from one point to another. This paper extends our previously published work on the flight patterns of Myotis velifer that have been observed in a habitat near Johnson City, Texas. Each evening, these bats emerge from a cave in sequences of small groups that typically contain no more than three or four individuals, and they thus provide ideal subjects for studying leader-follower behaviors. By analyzing the flight paths of a group of M. velifer, the data show that the flight behavior of a follower bat is influenced by the flight behavior of a leader bat in a way that is not well explained by existing pursuit laws, such as classical pursuit, constant bearing and motion camouflage. Thus we propose an alternative steering law based on virtual loom, a concept we introduce to capture the geometrical configuration of the leader-follower pair. It is shown that this law may be integrated with our previously proposed vision-enabled steering laws to synthesize trajectories, the statistics of which fit with those of the bats in our data set. The results suggest that bats use perceived information of both the environment and their neighbors for navigation.