While we routinely perform similar actions, we can never repeat any single action in precisely the same way. This is because we are constantly adapting our movements to compensate for changes in the state of the body (e.g., muscle fatigue) and world (e.g., a slippery sidewalk). Thus, each new action can be thought of as a form of generalization based on previous actions. Current theories seeking to explain the pattern of generalization rest on the idea that the brain's representation of motor behaviors is rooted in the physical features of movement, such as in the muscles and joints involved. This EArly-concept Grant for Exploratory Research (EAGER) project takes an alternate approach to consider more psychological aspects of motor behavior - such as whether an individual thinks that the goal of two given actions is the same and consequently the individual believes they should behave in the same way. Exploring the possibility that generalization may be governed by representations rooted in a psychological dimension will lead to a more comprehensive theory of generalization and greater effectiveness of practical applications. Modern society includes many tools and digital devices that people learn and interact with. Principles gleaned from this project will inform better design of tools that speed user learning by leveraging generalization of previously existing skills. Additionally, results of this work could optimize neurorehabilitation protocols for patients of stroke and other causes of loss of motor ability.

Approaches from the fields of motor control and cognitive psychology will be used to determine if the pattern of human motor generalization is better characterized by representations in a psychological space. First, to gain insight into psychological factors, participants will be asked to judge the perceptual and subjective similarity between two movements in various task configurations, which are common to traditional studies of motor generalization. Participants will then experience a standard sensorimotor learning task, the visuomotor rotation task, to determine how their judgments of psychological similarity predict how they generalize learning in one region of space to new regions of space. Correlations between the pattern of similarity judgments and the pattern of motor generalization will provide the first step toward establishing the influence of psychological factors on generalization. Next, the exploration of psychological factors will be deepened by determining if broader conceptual assumptions regarding the goals of the task govern the pattern of generalization. To test this idea, participants' knowledge of tool functions will be used to define a psychological similarity space. Here, participants will categorize various tools in terms of similarity and multidimensional scaling techniques will be employed to determine a distance metric between these tools in a psychological space. Participants will then train to move with these tools in the visuomotor rotation task to determine the extent to which generalization between tools is defined by their relative distance in a psychological space. Critically, throughout the project, the physical aspects of these movements will be controlled, such that any changes to the pattern of generalization will provide evidence in support of a more psychological representation underlying generalization. If successful, these studies will lead to a more comprehensive theory of human motor generalization, one that accounts not only for how the mind interacts with motor function in the manipulation of tools, but also how tool function may shape and influence mind and motor function.

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.

National Science Foundation (NSF)
SBE Office of Multidisciplinary Activities (SMA)
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Soo-Siang Lim
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Princeton University
United States
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