Temporal switching between binaural information sources.

An estimate of the rate of perceptual switching between two binaural information sources was sought by a procedure which employed an emergent perceptual property--the shape of the binaural sound image. Random polarity-modulated pulse trains were delivered to the two ears with controlled periods of interaural phase agreement and of phase disagreement. As the rate of alternation between the two interaural states is increased, discrimination suffers. With equal periods of phase agreement and disagreement, threshold periods of 2.2-3.4 ms, or about 300-450 alternations per second, are obtained. Such rates far exceed estimates of the rate of interaural switching obtained by other experimental paradigms. With unequal periods of agreements and disagreements, a minimum threshold period of 1.5 ms is the limiting factor. Large individual differences were noted. Other procedures for coding binary information yielded similar results. Rapid switching rate thresholds are obtained for narrow-band signals over a wide frequency range. A "central integration time" is identified with the threshold interaural switching period, and appears to be identical with the minimum integration time for monaural tasks.