Frequency discrimination thresholds: the effect of increment versus decrement detection of frequency

Difference limen for frequency (DLF) is traditionally tested using a frequency increment detection paradigm in which listeners are requested to distinguish between a reference tone and a series of comparison tones of higher frequency. Sporadic findings indicated that an increment paradigm is not necessarily comparable to a decrement paradigm, in which the comparison tones are lower than the reference tone. The purpose of the present study was to test whether the ability to detect frequency increments is different from that of frequency decrements. DLFs of 16 young women were measured at 200 Hz and 1,000 Hz, using detection of both frequency increment and decrement paradigms. Results indicated that: (1) the frequency increment detection paradigm was significantly smaller (i.e., superior) to the decrement paradigm for the DLF task at 200 Hz, (2) for both frequencies, the number of participants who exhibited better DLF using the frequency increment detection paradigm was significantly larger than the number of those who had better DLFs using the frequency decrement paradigm, and (3) for both frequencies, strong correlations were found between DLFs obtained in the increment versus the decrement paradigms. These results have implications: (1) to studies whose subjects may have reduced sensitivities at frequencies higher than the reference tone (such as the hearing impaired), and (2) to models related to the role of auditory feedback on voice accuracy and to the underlying processes of frequency discrimination.