What is Fear Conditioning?

Found this beautiful article while getting myself acquainted with "Fear Conditioning" which forms the basis of my lab work. I'm going to use this post to re-explain what I've understood with the goal of understanding it better.

Background:

The most famous example of conditioning is "Pavlov's dogs". Pavlov was studying digestion in dogs and coincidentally found out that dogs salivate not only at the sight of food but also upon hearing the footsteps of the feeder. 

Saliva contributes to the digestive process in more ways than one, so one would find it normal for the animal to start salivating when it's given food. An observer can then go a level of abstraction higher and explain why the dog starts salivating at the sight of food - the dog knows (consciously or not) that this food is eventually going to be consumed so it starts preparing for the digestion beforehand. In the same manner, the observer can then go a level of abstraction even higher and explain why the dog would start salivating at the sound of the feeder's footsteps. The dog knows that the sound of the feeder's footsteps implies the feeder is coming which implies food which implies consumption of said food which would require digestion which then necessitates saliva secretion.

All makes sense up till now, right? However, while explaining the last order of abstraction, the one involving footsteps, we glossed over a very important fact. The sound of the feeder's footsteps is, or would've at least started out as, a neutral stimulus. The dog would have no reason to believe it implies anything - good or bad. Repeated experiences of a particular kind has led the the dog to learn that these specific sounds imply something.

Learning:

Dogs, cats, horses, human beings, etc. are quite good at learning. We find our way through life by learning from experiences (consciously or unconsciously) and through reasoning (consciously). We discover associations and causal structures in this universe and then exploit the knowledge of these to get the things we want in life. (The article linked above has a beautiful line: "Humans must be sensitive to both meaningful and coincidental relationships between events in the environment to survive." I love how the authors highlight both 'meaningful' and 'coincidental' relationships, because the associations we discover may or may not be true. These false associations is what births superstition.) 

The article linked above says "Classical conditioning, also known as associative learning, is an unconscious process where an automatic, conditioned response becomes associated with a specific stimulus." In the case of Pavlov's dogs, release of saliva is the response being associated to the auditory stimulus of the sound of footsteps.

Fear Conditioning:

Pavlov's dogs were expecting food, so they started salivating. But what the animal learns through association may not always be pleasant. A particular dog may be mistreated by its owner and may "learn" to fear the sound of the owners keys jingling outside the door. A neutral auditory stimulus like the sound of the keys turning in the keyhole may elicit a conditioned fear response like elevated heart rate, increased sweating, anxious behavior, etc. Just like how the Pavlov's dogs example needed an unconditioned "positive" stimulus (actual food) upon which the neutral stimulus (sound of footsteps) can piggyback to elicit a similar response, in case of fear conditioning, we require an unconditioned aversive stimulus (pain of getting beat up) upon which the neutral stimulus (sight of the cruel owner, sound of owner's voice, etc) can build associations.