Experiments are reported on the effect of d‐amphetamine, sleep loss, and continuous intense crossear stimulation on the subjective judgment of octaves of high frequencies. Crossear stimulation produced significant decrements in the subjective octaves of 2000‐, 4000‐, and 8000‐cps tones. The administration of d‐amphetamine previous to crossear stimulation prevented decrements in the subjective octaves of 2000‐ and 4000‐cps tones. A significant depression of the decrement for the octave of an 8000‐cps tone was noted. Sleep deprivation also produced significant decrements in the pitch of the high frequencies studied. d‐amphetamine produced almost complete recovery of the decrement produced by sleep loss within one‐half hour of administration. Continued crossear stimulation, d‐amphetamine, and the combination of the two, failed to produce significant changes in loudness of the high‐frequency tones used. It can be assumed that all octave determinations were made at equal‐loudness levels, and that the shifts in octave judgments cannot be explained by pitch change with loudness. A theoretical model for pitch discrimination, located in the central nervous system, is discussed.

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