Auditory localization in the vertical plane: accuracy and constraint on bodily movement

In two preliminary experiments, listeners were instructed to limit increasingly the movement of their heads and/or bodies while attempting to localize narrow bands of noise centered on 2.3 or 8.3 kHz. With increasing constraint on movement, the high-frequency band was incorrectly perceived as elevated above the horizon. The low-frequency band, when actually elevated above the horizon, was not so regularly perceived incorrectly as being below the horizon, a finding inconsistent with a previous report. A third experiment, which more closely replicated the task conditions and strategies of the previous study, did tend to reveal the anomalous low-frequency error. The error is explicable as a default response to which listeners whose sensitivity to the vertical dimension, in general, appears imperfect are prone. From various reports, it emerges that about 25% of presumed normally hearing people exhibit this insensitivity.