Frequency and intensity discrimination in Mongolian gerbils, African monkeys and humans.

Frequency (delta F) and intensity (delta I) difference limens were directly compared in Mongolian gerbils (Meriones unguiculatus), Old World African Monkeys (Cercopithecus mitis, Cercocebus albigena), and humans. Methods employed a repeating background AX discrimination procedure, and positive (food) reinforcement for animals. For delta I, there were small quantitative differences between the species. At 1 kHz, 70 dB SPL, DLs averaged 2.82 dB for gerbils, 2.29 dB for monkeys, and 0.75 dB for humans. For delta F, there were larger differences between the species. At 1 kHz, 60 dB SPL, frequency DLs were highest for gerbils, averaging 108 Hz. DLs were lower for monkeys, averaging 32.6 Hz, similar to recently reported DLs for other Old World monkeys (Prosen et al., 1990). Human DLs, averaging 2.27 Hz, were markedly lower than those of either monkeys or gerbils. These results suggest that animals provide better models of human delta I than delta F.