A signal that tells an animal which behaviour will be reinforced if performed.

Cues can be verbal (“walk on”, “sit”, “step up”), physical (a leg aid, a hand signal, a lead movement), visual (a target stick, a hand gesture, a piece of equipment), or contextual (a particular location, a particular time of day, a particular handler). All of these and many other signals can function as cues once the animal has learned the relevant association.

A cue only becomes a cue through the process of learning. Until the animal has formed the association between the signal, the behaviour, and the consequence, the signal is just noise. This is one of the most useful framings in applied training because it makes clear that the cue itself does not “mean” anything intrinsic; the meaning is constructed by the animal’s learning history.

Cues operate across species in broadly similar ways. The same horse who responds to a verbal “walk on” might also respond to a click of the tongue, a touch on the shoulder, or a particular postural shift by the handler, depending on what they have been trained to. A dog can be trained to respond to dozens of distinct cues, each connected to a specific behaviour, and so can a parrot, a horse, a dolphin, or an elephant.

When cues are applied inconsistently, or when the reinforcement contingency around them is unreliable, the learned association weakens. This is cue dilution and is one of the most common causes of training problems across species.