Jeffress, L.A. (1944). Variations in pitch. Am. J. Psychol. 57, 63-76
The condition known to otologists as diplacusis binauralis dysharmonica, in which two pitches are heard when a single tone is presented alternately to both ears, has been known to psychologists for a long time. One of the experiments in Titchener's manual involves its measurement, and Stumpf devotes considerable space to the quality of the double-pitched tone that results from a single frequency when it is heard binaurally by a person having a serious diplacusis. In spite of its obvious bearing on theories of hearing, and in spite of occasional references to it in the otological literature, it has received almost no recent attention from psychologists interested in hearing. The only exceptions with which the writer is acquainted are his own mention of it in connection with its significance for the place theory, and a study by Stevens and Egan of its prevalence and magnitude in "normal" ears.
The writer has pointed out that one of the consequences of a strict pitch-place assignment in the cochlea should be a variation of the pitch-frequency relation from S to S, and in the same S from time to time. As we cannot reasonably expect this variation to be the same at all times in both cochleas, we should expect to find variations in the difference between the ears at different frequencies and at different times.
The work of Stevens and Egan has demonstrated the expected variation from S to S and has shown further that the direction and size of the difference in pitch for any single S varies irregularly with frequency. The present paper is concerned primarily with the possible variation of pitch differences with time.
1. Pitch differences between the ears were measured from time to time and were found to show variations large enough to be significant.
2. These variations were irregular and showed no agreement in direction nor in size for distant frequencies, but showed great agreement for frequencies close together.
3. Diathermy treatment of one ear produced no consistent shift in the pitch difference.
4. The results seem to be in agreement with the place theory of pitch and with predictions already made from it.