Two processes that can reduce cers are 1) extinction. Extinction happens with the repeated occurrence of a cs without the us. Counterconditioning happens when an alternative or competing response such as relaxation replaces the cr. People can learn to relax through the techniques of progressive muscle relaxation, autogenic training and meditation. Systematic desensitization involves having the target person become and remain relaxed while experiencing in vivo, imaginal or symbolic css from a stimulus hierarchy this method is very effective in reducing fears and other emotional behaviors. In vivo is usually more effective in reducing fears than imaginal or symbolic css. Functional assessment data and suds are used in developing a stimulus hierarchy. In vivo exposure therapies such as gradual in vivo exposure and flooding, present css but do not include relaxation as part of the process. Flooding is a technique in which the target person experiences intense, prolonged exposure to feared situations under the direction of a therapist.