The threshold for 500‐, 200‐, 100‐, 50‐, 20‐, and 10‐msec tones was measured with the tracking method at 250, 1000, and 4000 Hz in a group of five listeners who simulated a hearing loss of about 40 dB. A sample of listeners presenting with temporal lobe lesions was also examined. The results on both groups of subjects were remarkably similar to one another. That is, where the threshold difference between a 20‐ and 500‐msec tone is expected to be 10 dB, the differences observed here were in excess of 20 dB. In each instance, these aberrant results are interpreted not to be a result of a deficiency in the summing mechanism, but rather are due to a modification of the detection process.