Stimulus Discrimination

Due to the way that trauma memories are processed it is common for survivors of trauma to experience involuntary recollection of their trauma memories. These are often experienced with a ‘happening in the present’ quality and can be extremely distressing. Ehlers & Clark (2000) hypothesized that stimuli which were temporally associated with the traumatic event can act as triggers for involuntary recall of the trauma memory, and that over time these triggers may generalize from specific prompts closely associated to the trauma to broader categories of stimulus (stimulus generalization). This generalization results in a wider range of stimuli which can trigger feelings of distress, and can lead trauma survivors to act to avoid progressively wider ranges of situations. Stimulus discrimination is an effective treatment for this difficulty. Clients are guided to deliberately attend to differences between then (danger at the time of the trauma) and now (safety in the present).

Stimulus discrimination can be framed to clients as a ‘brain training’ exercise with the rationale that their mind is attending to stimuli associated with their trauma and incorrectly interpreting them as signs of danger in the here-and- now. Clients should be guided to:

1. Record where they were when their memories of the trauma were triggered. What was happening?
2. Attend to any similarities between stimuli in the here-and-now and stimuli that were present at the time of the trauma. Many clients will find this relatively straightforward.
3. Clients should then be directed to deliberately and effortfully attend to differences between the time of the trauma and the present moment. The ‘differences’ box guides clients to attend to sights, sounds, touches, smells, tastes, and knowledge. Clients can be encouraged to systematically attend to each of these and ask themselves “what is different between now and then?”
4. Once differences have been noted which lead to the conclusion that

• Ehlers, A., Clark, D. M. (2000). A cognitive model of posttraumatic stress disorder. Behaviour Research and Therapy, 38, 319-345.