Accounts of human fears and phobias based on current conditioning models using data from adults are examined and found wanting. Instead, the characteristics of human phobias resemble the kind of learning found during the amnesic period of infancy. As certain neural systems mature, conditioning begins to exhibit adult characteristics: context dependency, sharp generalization, and rapid extinction. Although direct behavioral control by the early learning systems wanes, the adult learning system seems to be structured at least/partially through the lasting influence of infantile experience. Under (hormonal) stress, residues of early experience are reinstated and incorporated into adult memory where they directly control behavior. This control exhibits infantile characteristics. The evidence suggests that once acquired, such conditional fears might never be eliminated using traditional extinction or counterconditioning procedures. The view leads to a renewed emphasis upon the role of experience in human development, accepting the disproportionate importance of infant experience as the foundation upon which subsequent learning and cognitive function rest.It is plain from clinical experience that certain patients experience critical incidents in which the fear has an onset. What is particularly interesting is the fact that quite frequently these same people have been exposed to the same stimulus repeatedly in the past without acquiring the fear. It seems that for acute onset fears, there are certain psychological states in which the person is vulnerable to the acquisition of fears. To take a clinical example, in those agoraphobic patients who report an acute onset of fear, one needs to know why the fear arose on the day that it did, at the time that it did. And why do they acquire a fear of public transport, crowded or open spaces, or whatever the content of their phobia, when on hundreds or thousands The first author acknowledges the fundamental contributions of David Furrow, Scon Mendelson, Michael Buttrick.