Learning to perceive pitch differences

Abstract

This paper reports two experiments concerning the stimulus specificity of pitch discrimination learning. In experiment 1, listeners were initially trained, during ten sessions (about 11,000 trials), to discriminate a monaural pure tone of 3000 Hz from ipsilateral pure tones with slightly different frequencies. The resulting perceptual learning (improvement in discrimination thresholds) appeared to be frequency-specific since, in subsequent sessions, new learning was observed when the 3000-Hz standard tone was replaced by a standard tone of 1200 Hz, or 6500 Hz. By contrast, a subsequent presentation of the initial tones to the contralateral ear showed that the initial learning was not, or was only weakly, ear-specific. In experiment 2, training in pitch discrimination was initially provided using complex tones that consisted of harmonics 3-7 of a missing fundamental (near 100 Hz for some listeners, 500 Hz for others). Subsequently, the standard complex was replaced by a standard pure tone with a frequency which could be either equal to the standard complex's missing fundamental or remote from it. In the former case, the two standard stimuli were matched in pitch. However, this perceptual relationship did not appear to favor the transfer of learning. Therefore, the results indicated that pitch discrimination learning is, at least to some extent, timbre-specific, and cannot be viewed as a reduction of an internal noise which would affect directly the output of a neural device extracting pitch from both pure tones and complex tones including low-rank harmonics.

Generalization of Frequency Discrimination Learning Across Frequencies and Ears: Implications for Underlying Neural Mechanisms in Humans

“…The present results contrast markedly with the earlier results by Demany and Semal (2002), which suggest that frequency discrimination learning takes a long time to generalize to novel frequencies after training at a single frequency. Indeed, Demany and Semal (2002) showed that following initial training at 3000 Hz, FDTs at two new frequencies (1200 and 6500 Hz) continued to decrease for several hours as listeners were now trained at these frequenciesV while at the same time, FDTs at 3000 Hz, which had already reached an asymptotic level earlier, showed no significant further improvement.…”

“…While the above-cited study by Demany and Semal (2002) and a recent study by Ari-Even Roth et al (2004) showed no significant ear-specificity in frequency discrimination learning, a former study by Delhommeau et al (2002) showed a slight, but significant, ear-specific component. Thus, half of the listeners in the present study were trained with stimuli presented to the right ear and the other half was tested with stimuli presented to the left ear.…”

“…Indeed, Demany and Semal (2002) showed that following initial training at 3000 Hz, FDTs at two new frequencies (1200 and 6500 Hz) continued to decrease for several hours as listeners were now trained at these frequenciesV while at the same time, FDTs at 3000 Hz, which had already reached an asymptotic level earlier, showed no significant further improvement. However, as suggested above, Demany and Semal did not check whether, under the stimulus conditions used in their study, FDTs did not stop to improve earlier at 3000 Hz than they would have at 1200 and 6500 Hz if these frequencies had been used as initial training frequencies; therefore, it is difficult to ascertain that the results of that study did not overestimate the frequency specificity of frequency discrimination learning.…”

“…In the visual modality, for instance, spectacular perceptual-learning effects have been demonstrated in texture-, contrast-, orientation-, or movement-discrimination tasks (e.g., Ahissar andHochstein 1996, 1997;Ball and Sekuler 1982;Berardi 1980, 1981;Sagi 1991, 1993;Karni and Bertini 1997;Schoups and Orban 1996;Ahissar 2001;Gilbert 1994Gilbert , 1996. In the auditory modality, considerable improvements in thresholds with practice have been shown in frequency-and duration-discrimination tasks (Ari-Even Roth et al 2003;Campbell and Small 1963;Delhommeau et al 2002;Demany 1985;Demany and Semal 2002;Grimault et al 2002Grimault et al , 2003Hawkey et al 2004;Irvine et al 2000;Wright and Fitzgerald 2005;Wright et al 1997). The mechanisms responsible for these improvements remain unclear.…”

“…While this has not been looked at in detail in previous studies, differences in the time course of learning at different frequencies might help to clarify discrepancies in outcomes among earlier studies. For instance, Demany and Semal's (2002) finding that FDTs at 1200 and 6500 Hz can still improve markedly with practice after FDTs at 3000 Hz have ceased to do so, which these authors interpreted as evidence for frequency-specific learning, might be explained differently if, for some reason, FDT improvements were found to take longer at the latter than at the former two frequencies. There are various reasons for which training-induced improvements in FDTs should not necessarily have the same time course at all frequencies.…”