In preparing this review an attempt was made to establish some sort of meaningful outline that would serve as a guide in arranging the varied auditory research to be reported upon. For this purpose, it appeared that the most satisfactory approach would be in terms of the functions of the auditory system as it serves as an information processing device. With this arrangement both behavioral and physiological investigations can be intermixed as they bear upon similar functional aspects of hearing. Admittedly, purely anatomical reports may not have much to say directly about function; however, such studies generally have functional implications and caa be fitted into the review without too much stress and strain. (See Table 1, Page 58). DETECTION STIIDIES O1¢ NORMAL FUI~CTIONII~G These studies can be divided into two categories: psychophysical studies, and physiological and anatomical studies. Psychophysical studies of thresholds of aud¢tlon.-Few studies were concerned primarily with determination of thresholds of audition as a function of test procedure; such a matter appears to have beerx well worked over, and greater interest has been expressed in threshold data as they bear .upgn various theoretical models. Hirsh (56) reviewed briefly the automatic Bekesy audiometer, indicating its differential diagnostic uses. Price (100), utilizing the BCkCsy audiometer and a pulsed tone, compared thresholds obtained from normal sweep frequency procedures and fixed frequency ascending and descending trials. He found that the midpoints of the continuous tracing agreed well with both fixed frequency ascending and descending trials. Melnick & Doerfler (83), however, found that descending and ascending trials yielded different thresholds, an error of habituation being evident. The differences may reflect differences in attenuation rate (Price failed to specify the rate for the fixed frequency trials) or the fact that Price used variable starting points (___ 15-30 dB) and Melnick & Doerfler fixed starting points of 4-40 dB. Zwislocki et al. (154) determined the threshold of audibility for short pulses. Assuming a memory factor, they found that pairs of pulses behaved as if simple temporal summation occurred, but that thresholds to multiple pulse trains reflect the analytical ability of the ear. Thus, as repetition rates increase and pulse trains become longer, critical bands narrow, and temporal summation is counteracted by the progressive narrowing of the frequency ranges over which the ear summates energy.
