How successful extinction and counterconditioning are, and how they work, is the source of some controversy, and some reason to see both methods as highly ineffectual (Bouton 2004). Although the traditional view is that extinction breaks associative bonds, it is an open empirical question whether extinction proceeds by breaking the previously created associative bonds, or whether it proceeds by leaving that bond alone but creating new, more salient (and perhaps context-specific) associations between the CS and other mental states (Bouton 2002, Bendana and Mandelbaum forthcoming). Additionally, reinstatement, the spontaneous reappearance of an associative bond after seemingly successful extinction, has been observed in many contexts (see, e.g., Dirikx et al. 2004 for  reinstatement of fear in  humans).[22]