A variation of the method of limits.
Stimulus intensity is progressively increased (ascending limits) until the observer reports seeing the stimulus, then is progressively reduced (descending limits), until the subject reports not seeing the stimulus.
The size of the steps must be chosen with care:
- Steps too large : the precision is compromised
- Steps too small : many presentation of the stimulus may be necessary.
Threshold is considered the average of several of these reversal points.
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Possible Errors:
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Staircase problem:
- The observer were trusted to report honestly whether or not they perceived a stimulus.
- ~Ex.: Staircase Method
