Auditory function was investigated in seven pigmented hooded rats (str
ain Long-Evans) with the aid of an operant conditioning procedure. Fre
quency difference limen was measured at frequencies from 0.5 to 64 kHz
at 50 dB sensation level (SL). Weber ratios (frequency difference lim
en/frequency) in this range varied between 3.7 and 7.3%. The decline i
n the intensity of the stimulus from 50 to 10 dB SL was accompanied by
a slight increase in the frequency difference limen. The frequency di
fference limen values were similar for frequency shifts upwards or dow
nwards. Intensity discrimination was measured at 50 dB SL at frequenci
es of 2, 8 and 32 kHz. Intensity difference limen was frequency indepe
ndent and amounted to 2.9+/-0.5 dB in conditions of upward intensity s
hift. The values of intensity difference limen measured in conditions
of downward intensity shift were significantly larger and amounted to
6.5+/-1.6 dB. The characteristics of hearing function found in these e
xperiments correspond with those described by other authors in albino
rats and indicate that albinism in the rat has no significant influenc
e on auditory frequency and intensity discrimination.