Primary reinforcer

A reinforcer that has inherent biological value to the animal and does not depend on prior learning to be reinforcing.

In horses, primary reinforcers include food, water, the relief of physical discomfort, social contact with familiar conspecifics, and access to safety or rest. A naive horse will respond to these reinforcers without needing to learn that they are valuable. The biological reward is built in.

Primary reinforcers are distinguished from conditioned reinforcers (also called secondary reinforcers), which acquire their reinforcing value through pairing with a primary reinforcer. A clicker only becomes reinforcing because it predicts food; food itself is reinforcing without any prior association.

The distinction matters practically because conditioned reinforcers depend on continued maintenance of the underlying primary reinforcer pairing. If the click is used repeatedly without food ever following, the conditioned reinforcer value extinguishes and the click stops working. Primary reinforcers do not extinguish in the same way (food remains food regardless of how often it is delivered), though they do show satiation effects: a horse who has just eaten will be less motivated by additional food than a hungry horse.

Different horses have different primary reinforcer hierarchies. Some are highly food-motivated; others find a well-placed scratch or quiet word more reinforcing than food in many contexts. Mykle, for example, is a deeply food-driven horse, but for maintenance work on established behaviours a scratch is the more practical primary reinforcer because it can be delivered cleanly without the food-related arousal that food would produce in him. The best primary reinforcer is the one the individual horse actually finds rewarding in the specific training context, not the one the trainer assumes should be most rewarding.