A form of learning in which the animal tries various behaviours and the consequences shape which ones are repeated.

A horse learning to open a stable door latch through trial and error, a dog working out how to get a treat from a puzzle toy, a parrot learning to manipulate a foraging device, a cat figuring out how to open a kitchen drawer to access the food inside, are all examples of trial-and-error learning. The animal generates variation in behaviour, the consequences differentially reinforce or fail to reinforce different attempts, and behaviour gradually shifts toward the successful patterns.

Trial-and-error learning underlies most operant conditioning and is one of the foundational learning processes across species. The term is sometimes attributed to psychologist Edward Thorndike, whose work with cats in puzzle boxes in the late nineteenth century systematically described the process. Thorndike’s “Law of Effect” (behaviours followed by satisfying consequences become more likely; behaviours followed by unsatisfying consequences become less likely) is the basic principle of trial-and-error learning.

Trial-and-error learning is more efficient when the animal is in a calm enough state to experiment. High-arousal animals tend to repeat the same responses rather than generating variation, which limits the trial-and-error process and slows learning. This is one of the reasons high-arousal training tends to produce less flexible learning than calmer training.

The process is also more efficient when the consequences are clear, timely, and consistent. Animals can learn rapidly through trial-and-error when each attempt produces a clear consequence the animal can recognise. Learning slows substantially when consequences are inconsistent, delayed, or unclear.

In applied training contexts, trial-and-error learning is harnessed through shaping and successive approximation, where the trainer deliberately reinforces variants of the behaviour that approach the desired goal while not reinforcing variants that do not. The trainer is providing the consequences that shape the animal’s natural trial-and-error process toward the trained outcome.