Observer efficiency and weights in a multiple observation task.

A sequence of seven tones, sampled from one of two distributions differing in mean frequency, is presented to observers who try to report which distribution was sampled. Estimates are obtained of the weight or importance given to each tone as a function of its temporal position. In five experiments, the reliability of the information is varied by changing the variance of the distributions; tones with high reliability are sampled from distributions with relatively small variance, whereas tones with low reliability are sampled from distributions with relatively large variance. Results show that the observations are weighted more efficiently when the tones have equal rather than unequal reliability, and when the most reliable tones have the greater intensity. Additional results show that the most intense tones often receive the greatest weight, even when those tones have the least reliability.