Brett Fajen - US grants

A child who runs through a swinging door does something in common with a bird that lands on a tree branch. Both cases produce soft collisions rather than avoiding contact altogether. Soft survivable collisions can also be made in circumstances that change dramatically in the attempt, consider the circumstances of a Navy pilot landing on the bucking surface of a carrier deck. To understand how people and animals succeed in their capacity for soft collisions, scientists must account for soft collisions in all these situations. With support from the National Science Foundation, Dr. Brett Fajen's research aims at understanding how people adapt to a wide range of conditions to successfully accomplish soft collisions or simply avoid collisions with obstacles in the path of motion. The research will be conducted using a simulator in which Dr. Fajen can systematically vary the task, environmental, and dynamic constraints, and observe how people adapt to such changes. The broader impacts of this project include applications to transportation safety, the design of mobile robots, teleoperation of vehicles from remote locations, and a deeper understanding of visual-motor deficits in humans. This project integrates research and education by supporting the development of two new courses at Rensselaer Polytechnic Institute, and providing opportunities for undergraduate and graduate students to participate in research

Crossing a busy street can be challenging. The pedestrian must carefully estimate the time and distance needed to reach safe ground, and compare these with estimates of the speeds and directions of potentially many vehicles as they speed by. The baseball player faces a similar challenge in estimating whether to chase down a fly ball or wait for it to bounce. These challenges illustrate how physical tasks often require one to implicitly and seemlessly take into account one's own perceptual and motor constraints. How do people know with such precision that a given action is or is not within the limits of their perceptual and motor systems, well before the action is initiated? This basic human ability is particularly impressive when one considers that perceptual and motor constraints change throughout life. For instance, maximum running speed may change as a result of training, injury, fatigue, surface traction, and many other factors. People effortlessly adapt to such changes, often without even being aware of them.

With support of the National Science Foundation, Dr. Fajen will investigate how humans perceive and act in ways that reflect their ever-changing visual and motor capabilities. Experiments will be conducted in a virtual environment laboratory so that aspects of the task and environment can be manipulated while participants actively engage in realistic perceptual-motor tasks. The results will further our understanding of the adaptivity of perceptual and motor systems. This knowledge may inform the remediation of visual or motor functions that are impaired due to injury or disease. It may also inform the design of prostheses, simulators, virtual environments and other artifacts that engage the adaptive powers of perceptual and motor systems.

DESCRIPTION (provided by applicant): This proposal outlines a program of research designed to investigate how visual information is used to guide locomotion to ensure safe and efficient navigation through the environment. More specifically, the long-term objective is to investigate the adaptive mechanisms that allow people to perform basic locomotor tasks in the face of variations in the dynamics of the body and the environment. Actors'movement capabilities are continually changing over both short and long time-scales as a result of injury, disease, neurological damage, aging, fatigue, growth, changes in load, and so on. Such variability has non-trivial consequences for the visual control of locomotion. The ability to adapt to these changes plays an essential role in supporting safe and efficient locomotion, and reducing the need for jerky, corrective movements that often result in losing balance, falling, and colliding with obstacles. An important next step in understanding the visual control of locomotion is to investigate how people perceive the world and control their movement in ways that take into account their ever-changing movement capabilities. The research described in this proposal is aimed at addressing the following questions about locomotor adaptation: (1) What components of optic flow drive adaptation to changes in locomotor capabilities? (2) To what extent does adaptation generalize to conditions and tasks that differ from those in which learning occurs? (3) To what extent should we attribute the reliability with which people take their movement capabilities into account to (a) internal adaptive mechanisms, and (b) information about one's locomotor capabilities that is picked up on the fly? Experiments will be conducted in a large-area virtual environment laboratory equipped with a head-mounted display and motion tracking equipment. Subjects will perform a variety of locomotor tasks, including turning toward goals, avoiding obstacles, intercepting moving targets, regulating gait to step on safe footholds, and selecting routes. The results will provide a foundation of knowledge for understanding the development, acquisition, and maintenance of locomotor skills, and for improving therapy programs that promote adaptation to changes that affect one's locomotor capabilities. PUBLIC HEALTH RELEVANCE: Locomotion is an integral part of many routine, daily activities. Changes in movement capabilities brought about by aging, injury, disease, fatigue, or use of a prosthetic limb pose a serious threat to one's ability to safely and efficiently navigate through complex, dynamic environments. The ability to adapt to these changes plays an essential role in supporting safe and efficient locomotion, and reducing the need for jerky, corrective movements that often result in losing balance, falling, and colliding with obstacles. The research described in this proposal is aimed at understanding the mechanisms that allow for adaptation of the visual-locomotor system. The results of this project will provide a basis for designing physical and occupational therapy programs that promote rapid and complete adaptation, allowing people whose movement capabilities become impaired to recover basic locomotor functions.

Mobility is an integral part of many daily activities. Problems that affect a person's mobility can significantly impact lifestyle, independence, work and social life, and overall health. More often than not, walking from one place to another involves avoiding obstacles and dealing with uneven or slippery surfaces. In this project, the investigators will study how people walk through complex terrain, such as a cluttered room, a city street, or a backwoods trail, while maintaining biomechanical stability and energetic efficiency. The findings may help health-care practitioners better anticipate the complex consequences of visual and motor impairments for the many daily activities that involve walking and decide which specific aspects of visual and locomotor capabilities need to be improved to prevent trips, slips, and falls. The research also has implications for the development of biologically inspired walking robots.

The primary objective of the project is to understand how people use visual information to adapt walking to the upcoming terrain and take advantage of forces that are generated during walking to enhance stability and energetic efficiency. The experiments are designed to determine why visual information about certain areas of the upcoming terrain must be available at certain times, why people choose one place to step rather than another when more than one option exists, and how people rapidly adapt to sudden, unexpected changes in the position of a desired foothold. The findings from these experiments will inform the development of theory that synthesizes research from robotics, biomechanics, and vision science, and will lead to a principled understanding of how people achieve high levels of energetic efficiency and stability while walking over complex terrain.

The ability to guide one’s movement through the world on the basis of vision plays an essential role in many daily activities, from routine behaviors such as walking through crowded spaces to skilled tasks such as steering a tractor-trailer along a mountain road. Oftentimes, humans and other animals must move at high speeds through densely cluttered environments, avoiding obstacles, squeezing through narrow openings, and following winding paths to reach their goals. To perform such tasks safely and efficiently, it is not enough to focus entirely on the most nearby objects. Skillful navigation also relies on the ability to look farther ahead and anticipate the need to reach goals that lie beyond the immediate future. This project will investigate how people visually guide their movement to satisfy goals over multiple time horizons. It is novel in its focus on tasks that push the limits of human visual-motor performance to the extreme and that could inform the development of semiautonomous driver- and pilot-assist technologies. The research will benefit society by revealing new visual control strategies that could be adapted for use on robots to produce more skillful and human-like behavior. <br/><br/>The ability to adapt behavior in anticipation of future goals is often assumed to reflect elaborate cognitive processes such as path planning that rely on internal models. However, there are very few empirical studies of anticipatory steering behavior and the possibility that such behavior could be captured without invoking internal models has not yet been seriously considered. This project combines experiments on steering and gaze behavior in humans with mathematical modeling to explore how humans guide their movements to satisfy both immediate and future constraints on their trajectory. Using a custom-designed, virtual reality drone piloting simulator, the researchers will study the steering and gaze strategies that humans use to navigate through a series of waypoints and will conduct experiments to reveal how and in what conditions humans adapt their movements in anticipation of future goals. They will also use modeling and simulation to determine whether anticipatory steering behavior can emerge without model-based path planning. Lastly, a suite of research tools for conducting experiments in virtual reality and for processing, analyzing, and visualizing gaze data will be developed and made available to the scientific community.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.