Measuring flicker thresholds in the budgerigar.

A method of measuring thresholds in animals is described and illustrated in the case of flicker fusion in the budgerigar. After training with reinforcement for pecking at a high-frequency light (115 Hz) and nonreinforcement for pecking at a low-frequency light (20 Hz), subjects were given threshold trials and reinforcement trials mixed randomly in equal number. In threshold trials (no reinforcement), the target began flashing at 115 Hz and decreased in flash rate with each peck until the subject stopped responding. During reinforcement trials, the target continued to flash at 115 Hz, and responses were reinforced on a variable-ratio schedule. Flicker thresholds obtained from two birds showed a linear relation to the logarithm of intensity in accordance with the Ferry-Porter law.