Evidence for a hierarchical structure underlying avoidance behavior.

In studies on avoidance learning, a warning signal is followed by an aversive unconditioned stimulus unless the participant performs a designated response. The authors examined whether avoidance behavior can be based on hierarchical knowledge, that is, knowledge about the conditions under which certain relations hold. In the present study, a single avoidance response had different effects depending on the nature of the warning signal. Results showed that participants acquired this hierarchical knowledge and used it to avoid negative outcomes. The results are in line with an occasion setting account of avoidance learning and can be explained also by a modified version of Lovibond's (2006) account of avoidance learning.