The Sensible Senseless Person: a theoretical framework for clinical assessment of proprioception

Proprioception, the sense of body position and motion, is essential for all motor activities. Position-matching is a common task used to assess proprioceptive acuity. This assessment is limited due to reliance on self-report, and biased performance measures. To support this statement, we introduce the concept of a "sensible senseless person" (SSP), a theoretical construct that lacks sensory perception but is capable of logical inference. This framework allows for critical examination of the validity of conventional performance measures used in position-matching tasks. Our analysis reveals that traditional measures are influenced by the structural parameters of the task, strategic responses, and the prior beliefs of the SSP. To address these limitations, we propose a novel performance metric: the Guess Index (GI). Unlike existing measures, the GI is designed to be robust against these confounding factors, ensuring that the SSP would consistently receive the same score. To demonstrate the utility of the GI, we applied a simplified, clinically-oriented version of the position-matching task to healthy individuals and persons with stroke. Our findings show that the GI is more sensitive to group differences than traditional measures and is the only metric capable of correctly classifying persons with stroke above chance level.