Consequences of parameter learning in experiments on immediate auditory memory

In a recent paper we described the decay of auditory memory for patterns consisting of ten 40‐msec tones played in sequence. On each trial, one of 50 permutations of a ten‐tone catalog was played, and then it was repeated either with or without a frequency increment (Δf) added to one of the ten tonal components. The interval between the two patterns was varied from 0.5 to 32 sec. The frequency increments became only slightly less detectible as the interstimulus interval was lengthened (just‐detectible values of Δf increased by about 1/3). In a new experiment, the same highly trained listeners were able to make almost as precise discriminations without a standard present on each trial. When the patterns consisted of ten‐tone sequences drawn from a 1000‐tone catalog the listeners could no longer perform at better‐than‐chance levels in the remembered‐standard conditions. The results begin to establish the limits of listeners' ability to learn the parameters of a catalog from which acoustic stimuli are sampled. [Supported by Grant No. NS03856, National Institute of Neurological Diseases and Stroke, Department of Health, Education and Welfare.]