Pigeons' delay discounting functions established using a concurrent-chains procedure.

Oliveira et al. (2014) worked with pigeons in a lab. They wanted to know if a new way to measure delay discounting gave the same answers as the old way.

The team used two setups side-by-side. One was the classic adjusting-amount task. The other was a concurrent-chains procedure. They compared the curves each method produced.

Both methods gave the same hyperbolic discounting curves. The shapes sat on top of each other. No statistical difference appeared.

The new concurrent-chains tool is valid. You can swap it in for the standard task when you study how delays weaken reward value.

Grosch et al. (1981), Cullinan et al. (2001), and Lattal (1984) used similar pigeons and concurrent-chain schedules years earlier. They looked at signaled versus unsignaled delays, not discounting curves. Their work built the chassis; Luís et al. added the speedometer.

Kuroda et al. (2014) ran at the same time and also used delay signals in pigeons. They asked how signals help discrimination, while Luís asked how signals fit discounting. Same lab world, different questions.

Killeen (2015) and Killeen (2020) later offered new math for discounting. They did not test animals, but their formulas can now be applied to the clean curves Luís captured.

If you run basic animal studies, you now have two interchangeable ways to plot how delay kills value. Pick the one that fits your cage layout. Either will give you the same hyperbolic line, so you can spend your time asking bigger questions instead of worrying about the tool.