Perceptual learning was used to examine mechanisms of pitch perception. Thresholds (FODLs) were measured for discrimination of the fundamental frequency (F0) of a complex tone with a nominal F0 of 100 Hz and cosine-phase harmonics, bandpass filtered into one of three frequency regions, LOW (harmonics 1-5), MID (harmonics 11-15), and HIGH (harmonics 28-32). Tone LOW contained resolved harmonics, conveying both place and temporal fine structure (TFS) information. Tone HIGH contained only unresolved harmonics and conveyed only temporal envelope information. Tone MID probably conveyed TFS information but not information about individual harmonics. All tones were presented in threshold equalizing noise. Fifteen subjects were tested over a period of 10 days, 2 for measurement of pre-training thresholds, 6 for training, and 2 for measurement of post-training thresholds. In the pre-training and post-training sessions, all subjects were tested using all three tones. Subjects were divided into three groups of five subjects for the training sessions: each group was trained with one stimulus type. The group trained with LOW stimuli showed a large training effect, with transfer to the MID stimuli, but no transfer to the HIGH stimuli. The group trained with MID stimuli showed a large training effect, with transfer to the LOW stimuli and no transfer to the HIGH stimuli. The group trained with HIGH stimuli showed no training effect for any stimuli. The results suggest that similar pitch mechanisms were used for F0 discrimination of the LOW and MID stimuli, and that a different mechanism was used for the HIGH stimuli. It is proposed that the LOW and MID stimuli were both discriminated on the basis of TFS information, in the former case TFS information about individual resolved harmonics, and in the latter case TFS information about the periodicity of the waveform evoked by interfering harmonics.
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