Figure 7. Hypothesis sensitivity to assumptions.
(a, b) Human response to 5-degree perturbation vs. hypothetical responses with adaptation latencies of 50, 75, and 100 ms. (c, d) Human response to 5-degree perturbation vs. hypothetical responses with exponential convergence rates of 4·10−4, 8·10−4, and 12·10−4. Note that neither the latency nor convergence rate affects the time-domain response of the time-based reference because the perturbation automatically brings the ankle angle to the nominal inclined trajectory with respect to a temporal sense of phase. The two hypotheses are fairly insensitive to the latency and convergence rate assumptions, and in all cases the trend of the human response is predicted by the phase variable hypothesis.