Figure 3.

Hypothetical threshold tracking with the transformed up-down procedure. The plus sign represents the correct responses whereas asterisk represents the incorrect responses. The starting stimulus level is 6. The total number of reversals is 12. The first four reversals are performed with a step size of 1 and the successive eight are performed with a step size of 0.5. Note how the transformed rule lengthens the threshold tracking in comparison with the method of limits or the simple up-down procedure (see Figure 2).