Declarative knowledge Knowledge about what to do in a situation; this knowledge typically is verbalizable. Degrees of freedom The number of independent elements or components in a control system and the number of ways each component can vary Degrees of freedom problem A control problem that occurs in the designing of a complex system that must produce a specific result. The design problem involves determining how to constrain the system's many degrees of freedom so that it can produce the specific result. Dendrites Extensions from a neuron's cell body that receive neural impulses from other neurons; a neuron may have none or as many as thousands of dendrites. Descending tracts Motor neural pathways that descend from the brain through the spinal cord. Descriptive KP A verbal knowledge of performance (KP) statement that describes only the error a person has made during the performance of a skill. Diencephalon A component of the forebrain located between the cerebrum and the brainstem: it contains the thalamus and hypothalamus Discrete motor skill A motor skill with clearly defined move- ment beginning and end points, usually requiring a simple movement Discrimination RT The reaction time when the situation involves more than one signal but only one response, which is to only one of the signals; the other signals require no response.