Auditory intensity discrimination in blackbirds and pigeons

Area of Science:

• Auditory perception in animals
• Comparative psychoacoustics
• Animal behavior

Background:

• Understanding avian auditory capabilities is crucial for ecological and evolutionary studies.
• Previous research has primarily focused on auditory thresholds rather than intensity discrimination.

Purpose of the Study:

• To determine the intensity difference limens (DLs) for auditory stimuli in three avian species.
• To investigate the influence of sensation level and frequency on avian intensity discrimination.
• To compare avian intensity DLs with those of mammals.

Main Methods:

• Operant conditioning techniques were used to train redwing blackbirds, brown-headed cowbirds, and pigeons.
• Birds were trained to detect small increases in the intensity of pulsed tone trains at .5, 1.0, and 2.0 kHz.
• Some subjects also detected decreases in sound intensity.

Main Results:

• All three avian species exhibited similar intensity difference limens (DLs) across tested frequencies.
• Intensity DLs decreased as sensation level increased, with steeper slopes at 2.0 kHz.
• Median intensity DLs at 50 dB sensation level ranged from 2.7 to 3.3 dB.
• Detecting intensity decreases resulted in DLs 2-3 times larger than detecting increases.

Conclusions:

• Avian intensity discrimination is frequency-dependent and improves with increasing sensation level.
• Birds show greater difficulty in detecting sound intensity decreases compared to increases.
• Avian intensity DLs appear to be approximately 1-2 dB higher than those reported for mammals.