What is Learning?

I would define learning as a "durable change in behavior brought about by experience."  Learning and memory are connected.  The acquisition of new information or skills comes from instruction or experience.  Then, memory allows this new information to be stored and recalled when necessary.  Let's take the example of a person touching their finger to a hot burner.  As their finger touches the burner, a reflex mechanism causes them to quickly take their finger away.  This reflex happens so fast that the incoming message doesn't even have a chance to get to the brain before a reaction takes place.  However, while the reflex was coming into play to protect the finger, another message continued up to the brain for the person to process what had just happened.  It is here that learning occurs.  The person now knows that touching a hot burner is something unpleasant and should be avoided. They have learned from the experience and will change their behavior when next presented with a hot burner near their hand.  If only the reflex mechanism was in place, even though the finger would be taken off the burner, the person would not learn to avoid this situation in the future.

Another example in physiology is when a hormonally driven behavior becomes a learned behavior.  When a young stud dog first encounters a bitch in heat, his reproductive system kicks in and he instinctually exhibits breeding behaviors.  At this point, his endocrine system is responding to the bitch's endocrine system.  If this dog is used for breeding, he starts to learn that bitches in heat mean "time to breed."  He remembers what to do when presented with a bitch in heat.  Later in life, if experienced stud dogs are castrated, taking away the hormones that were the driving force of the breeding behavior in the first place, they will still willingly breed bitches.  The experience of breeding has produced a durable change in behavior.  

A similar situation occurs in breeding stallions.  When stallions are first bred, they need natural instinct and drive in order to breed the mare.  Some valuable stallions have their semen collected and need to "learn" how to mount a phantom mare in order to be collected in an artificial vagina.  Well, a phantom mare is a large vinyl covered metal object that is completely inanimate and is of no interest to a passing stallion in any way.  However, leading a mare in heat close to the phantom mare excites the stallion to instinctually mount.  He is guided onto the phantom while he perhaps thinks he's mounting the real mare.  After that, the real mare in heat can be placed in a set of stocks in the same room as the phantom and the stallion will mount the phantom just by visual and olfactory stimulation from the presence of the mare.  Many stallions who are collected often will no longer need a mare in heat present in order to collect.  When they see a phantom, they act like it is a mare in heat and will mount the phantom without any other stimulation.  This stallion has learned from experience that when he sees the phantom, he gets collected. This experience has changed his behavior in the presence of an ordinarily benign object and I would define this as learning.