Haptic Perceptual Instruments

University Of Connecticut, Storrs CT

Investigators

Abstract

Haptic Perceptual Instruments Claudia Carello, Till Frank, and M. T. Turvey Although it is common to think of haptics -- the sense of touch -- chiefly as a skin sense, its role as a muscle sense allows moment-to-moment control of the body that is crucial to moving in and interacting with the environment. Maneuvering tools with the hands and traversing surfaces with the legs involve the deformation of muscles and connective tissues. Such maneuvering is accomplished by what the research team of Claudia Carello, Till Frank, and Michael Turvey at the University of Connecticut have called "haptic perceptual instruments." Their NSF-funded research addresses the contribution of this muscle sense to the perception of distances traveled by legged locomotion (e.g., walking, skipping, galloping, etc.) in the absence of visual input. Preventing participants in the research from looking where they are going allows for the "pure" measurement of haptic perception. Humans, other mammals, insects, and arachnids can measure distance traveled strictly by the motions and forces generated by walking and running. Such perceptions are examples of the possibly universal ability of "mechanical intelligence." Experiments with humans suggest parallels between mechanical intelligence and certain basic memory principles. Just as memory is commonly evaluated via study and test so, too, is legged locomotion: judging distance on an outbound excursion from point A to point B is likened to the study phase and matching that distance on the return excursion from point B to point A is likened to the test phase. Typically memory performance is better the more similarities there are between study and test on a wide variety of factors, such as external environment (e.g., physical location), internal mental state (e.g., mood), and the mental strategy used to process the information during study and test (e.g., use of mental imagery as a mnemonic). For blindfolded legged locomotion, it is proposed that the crucial common factor is provided by a mathematical classification of locomotion patterns (technically called "symmetry groups") . In the planned research, when the outbound and return gaits belong to the same category (such as walking and jogging), return distances are expected to accurately match the outbound distances and to be independent of a variety of important variables -- speed, direction, inertial load, step size, and delay of measurement. On the other hand, the two distances should not match when the two gaits are from different categories (such as walking and skipping). In technical terms, Carello, Frank, and Turvey propose a nonlinear dynamical model which treats the outbound and return gaits as a single coupled haptic perceptual instrument, with a method for identifying and quantifying the instrument's attractors (stable patterns that the movements tend towards) and "noise" (variability around the attractor patterns). The use of such a formal mathematical model for studying the psychology of perception and action is an important development. The researchers hope to provide a theoretical and experimental foundation for understanding, at both behavioral and neurobiological levels, the process of path integration based on movement-generated information. The planned research will introduce new ideas for studying perceptual capabilities grounded in muscle sensibility. Uncovering commonalities between using the muscle sense to perceive objects (the team's previous research) and using the muscle sense to perceive environments (the planned research) promises to lay a foundation for a deeper and broader understanding of the role mechanical contact plays in the perception and memory functions of the haptic system. The project will expand and enhance the training typically received by psychology students by combining courses in physics and mathematics and courses in cognition and neuroscience. Importantly, identifying conditions under which the motions and forces generated by legged locomotion lead to successful or unsuccessful perception of distance traveled will provide novel hypotheses about the nature of locomotion disorders and their rehabilitation.