Internal models for object manipulation: Determining optimal contact locations

Abstract

Although there are an infinite number of ways that humans can lift an object, they tend to reach in a predictable manner. This suggests that people are aware of, and optimizing, some sort of loss function. This paper outlines a natural loss function that may be used to predict people's actions in everyday reaching tasks. The loss function is based on the physics of object manipulation and the assumption that people are planning for the intended motion of the object. Using this framework, we are able to make predictions about how people should reach if they are minimizing their expected risk. To test the model, we required people to reach to objects at varying orientations. Our experimental results indicate that people are reaching in a manner that minimizes their expected risk for the task. These findings suggest that people planning for the intended motion of the object and that our brain is aware of the physics involved with object manipulation.