Russell A. Powell, et al. Introduction to Learning and Behavior, 3rd Edition. 2009
Researchers also suggested…that a history of successfully overcoming minor adversities might immunize a person against depression when the person is later confronted by more serious difficulties (366-7)
(Experiment of Learned Helplessness by Nixon, Ph.D Developmental Psychologist at Penn State)
"Masserman’s Experimental Neurosis"「実験神経症」
As a general rule, traumatic symptoms are more easily induced in animals when the aversive stimulus is delivered in an environment that the animal has long associated with safety or some type of appetitive event. For example, unpredictable shocks delivered in a setting in which the animal typically eats food are especially likely to induce neurotic symptoms (Masserman, 1943). This suggests that symptoms of PTSD are more likely to arise when a person is, for example, unexpectedly attacked in the safety of his or her own home as opposed to a strange or dangerous area of town. The person who is attacked at home generalizes the experience and perceives the world at large as a dangerous, unpredictable place, with the resultant that he or she thereafter remains constantly vigilant (369).
"Learned Helplessness"「学習性無力感」
Learned Helplessness has also been related to certain forms of depression (Seligman, 1975). People who suffer a series of uncontrollable aversive events – loss of a job, pysically illness, divorce, and so on – may become extremely passive and despondent. Like animals exposed to inescapable shock, they show little interest in improving their lot in life (366).
Researchers have discovered a way to eliminate learned helplessness...behavioral treatments for depression often involve encouraging the patient to accomplish a graded series of tasks, starting with relatively minor task, such as writing a letter, and progressing to more difficult tasks, such as seeking a new job (Seligman, 1975).Researchers also suggested…that a history of successfully overcoming minor adversities might immunize a person against depression when the person is later confronted by more serious difficulties (366-7)
"Sensitizatization"「鋭敏化」
Sensitizatization is an increase in the strength of an elicited behavior following repeated presentations of the eliciting stimulus. For example, soldiers under attack generally do not habituate to the sound of artillery shells exploding nearby. Instead, their startle reaction grows stronger. Needless to say, this greatly contributes to the stress they experience and the inevitable breakdown virtually all soldiers suffer after repeated exposure to battle conditions (though Hollywood would often have you think otherwise)(97).
Watson and Rayner’s “Little Albert” 「アルバート坊や実験」
The importance of classical conditioning and overgeneralization in the development of phobia was first noted by John B. Watson and his student Rosalie Rayner.…they attempt[ed] to condition a fear response in an 11-month-old infant named Albert.
Watson and Rayner (1920) paired the loud noise with the white rat (Neutral Stimulus). Albert “jumped violently and fell forward, burying his face in the matress”...Albert was then subjected to further pairings of the rat with noise, during which he became more and more fearful.
Albert showed not only a fear of the rat but also of objects that were in some way similar to the rat, such as a rabbit, a fur coat, a dog, and even a Santa Claus mask. In other words, Albert’s fear response had generalized to objects that were similar to the original CS (conditioned stimulus).
By contrast, real-life phobias usually require only one paring of the US (unconditioned stimulus) with the CS to become established, and they often grow stronger over time (182-5).
Latent Inhibition
The phenomenon whereby a familiar stimulus is more difficult to condition as a CS than is an unfamiliar (novel) stimulus (151). 
