Ascending-descending threshold differences and internal subjective judgment in CFF measurements

The purpose of this study was to measure, using the method of limits, the ascending-descending threshold difference (delta = fa-fd) in normal subjects and its variation with repetition of the task two weeks after the first session. Sample mean values scored in the two sessions were close to zero and positively correlated. The ascending-descending difference was suggested to be likely related to the internal judgement of the subject.