A specific phobia can be acquired through classical conditioning. Classical conditioning occurs when you pair a conditioned stimulus (CS) which is a neutral stimulus (i.e. sight of a dog), with an unconditioned stimulus (US) which affects one of the senses (i.e. a bite hurts). So the US results in an unconditioned response (UR) (i.e. pain and anxiety). With enough repeated pairings of the CS and US, just presenting the CS alone (i.e. dog) may be enough to elicit a conditioned response (CR) (i.e. feelings of pain and anxiety).
So this is how a specific phobia can develop through classical conditioning, where in this example, the CS is the sight of a dog and the US is the pain that results from being bitten, with the resultant conditioned fear of dogs.
