Measuring flicker thresholds in the budgerigar.

Two budgerigars learned to tell steady light from flickering light. The birds pecked a key when the light held still and skipped pecking when it flashed.

Researchers slowly raised the flash speed until the birds could no longer spot the difference. These extinction probes revealed each bird's flicker threshold.

The budgerigars' thresholds followed the Ferry-Porter law. This law says faster flashes need brighter light to be seen.

The same rule holds for humans, so the birds' vision scales like ours.

Schusterman (1966) did the same job with pigeons but used conditioned suppression. The 1971 study swapped suppression for simple extinction probes and still got clean data.

Williams (1974) later used the same peck-key setup to show afterimages in pigeons. Together these papers prove one small rig can answer many vision questions.

Demello et al. (1992) moved from flicker to grating acuity in hens. The toolkit keeps working when you change both the bird and the visual task.

You can borrow this cheap, fast method any time you need a threshold. Run a few trials, drop reinforcement, and watch the response rate fall off. The point where pecking fades marks the sensory limit. No fancy gear, no long training, just clean data.