When we think of learning, we think of conscious learning. The ability to remember a telephone number, a new language or solving an equation. On the animal level, conscious learning could also be providing conscious cues to a dog that he has learned means roll over, stay, or come to me.
There is another kind of learning. A learning that is controlled directly by our nervous system and does not require thinking or conscious interaction. This is true for both humans and animals. This type of learning is called Classical Conditioning. Classical Conditioning will only take place if a human or an animal is rewarded or punished for a behavior. You learn a telephone number and the reward is not having to look it up each time you want to dial it. A dog learns to roll over and the reward is a dog biscuit. Humans and animals also learn as a result of unpleasant stimuli. A child only has to touch a hot burner once and will never approach it again. While a dog may not understand the words you say, when you raise your voice, a well-trained animal will immediately pay attention and perhaps cower because in the past, that raised voice was accompanied by a physically unpleasant stimulus.
There is a particular type of classical conditioning called Taste Aversion Conditioning, in which animals learn to avoid certain foods because in the past, contact with those foods resulted in some discomfort for them. Sheepherders have used this natural process to stop wolves from eating their sheep, without having to kill the wolves, which in a number of areas is illegal. Sheepherders learned to treat the mutton with a non-toxic substance that would make animals that eat the meat dizzy and nauseous. They would disperse the treated mutton at some distance from the herding sheep. Wolves that encountered the mutton lying on the ground would readily eat this free, no work meal. They would soon become dizzy and nauseous, however the effects do not result in any permanent harm to the wolf.
After encountering and eating the treated mutton a few times, the wolves learned to pass it by. However, when they approached the sheep, they would pick up the same scent, and if nipped, the same taste as the mutton. The wolves would immediately withdraw leaving the sheep alone. Since the substance added was odorless and basically tasteless, the wolves associated the dizziness and nausea with the smell and taste of the mutton. In the same way a child might associate a burn received from a burner on the stove, with the stove itself and avoid the entire stove of perhaps even, that area of the kitchen in which the stove happens to be.
Our Squirrel Proof Birdseed Products work in exactly the same way. Without harming the squirrels, they soon associate not only the smell of the hot birdseed with the discomfort of eating pepper coated seed, they also begin to avoid all the stimuli associated with that seed, specifically, the feeder itself.
Birds, on the other hand, having no capsaicin (pepper) receptors will not be conditioned to avoid the birdseed that contains chili pepper. For additional information about aversion conditioning refer to any basic text book in psychology or animal behavior.