Shock sensitization of startle: learned or unlearned fear?

Following shock, rats exhibit a potentiated startle response to a sudden, loud noise. It has been suggested that this shock sensitization of the startle response can be used as a model preparation for studying unlearned fear. After reviewing the theoretical and empirical bases for this claim, the results of several recent studies that show that the shock sensitization of startle effect is actually mediated by contextually conditioned fear are presented. From this, it is concluded that the shock sensitization of startle procedure is an appropriate model preparation for studying contextual conditioning but is not an appropriate procedure for studying unlearned fear. Several other procedures that have potential as model preparations for studying unlearned fear are discussed briefly.