The first hundred steps with robotic assistance. The steps shown correspond to steps 391–491 in Figure 4. The values from Figure 4E are made negative to better visualize the decay of robotic assistance. A: Assistance as Needed protocol. Each line is data from one of the ten subjects. B: Assistance as Needed with Noise Insensitivity protocol. This assistance algorithm took into account variability in stepping height around the desired mean. Here we used a weighed error band and decreased the importance of errors within a range of normal fluctuation. When subjects exited this range, the robot assistance transiently increased C: Assistance-as-needed with Improper Parameter Selection protocol. We set the robot forgetting factor greater than the human forgetting factor (fR > fH). This created a situation in which the robot took over the task of compensating for the virtual impairment from the subjects, not allowing the subjects to learn a model of the virtual impairment. Four subjects participated in this last protocol.