Threshold from up-down staircases is the averaged level at response reversals.

Evidence

Experiments commonly use either a “2-down 1-up” or a “3-down 1-up” staircase procedure to estimate threshold. In the 2-down 1-up procedure, a listener must make a correct decision on two consecutive trials before the stimulus level is decreased. A single missed detection causes an increase in signal level. In contrast, three consecutive stimulus detections are required for a decrease in signal level in the 3-down 1-up procedure. In these procedures, threshold is determined by averaging the signal levels at the reversals, or the stimulus levels at which listeners’ responses Figure 2-15. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 320

Categorization

• DEFINE: Explains the up-down staircase decision rules and defines ‘reversals’ as the response-turn points that threshold is averaged from.
• QUESTION: Why does ‘2-down 1-up’ vs ‘3-down 1-up’ change the accuracy of the estimated threshold — what points on the psychometric function does each procedure converge to?