This resource helps clients distinguish between past trauma and present safety, reducing distress related to trauma triggers.
Offers theory, guidance, and prompts for mental health professionals. Downloads are in Fillable PDF format where appropriate.
Includes client-friendly guidance. Downloads are in Fillable PDF format where appropriate.
An editable Microsoft PowerPoint version of the resource.
Stimulus discrimination - often referred to as 'then vs. now' - is a therapeutic exercise designed to help trauma survivors differentiate between past traumatic events and present safety. By focusing on current sensory experiences and comparing them with past trauma, clients can reduce involuntary and distressing trauma recollections. This method is particularly effective in reducing symptoms of post-traumatic stress disorder (PTSD), helping clients realize (cognitive and then emotionally) when they are genuinely safe, and mitigating avoidance behaviors.
Stimulus Discrimination offers a structured approach for clients to manage involuntary trauma memories, promoting a sense of safety in the present.
Re-experiencing symptoms and avoidance related to trauma triggers.
Note the situation when the trauma memory was triggered.
Identify similarities between current experience and past trauma, work across sensory modalities.
Focus on differences between current experience and past trauma, work across sensory modalities.
Direct attention to present sensory details to highlight differences.
Encourage self-soothing and affirm current safety.
Use these insights to reduce future trauma reactions.
Stimulus discrimination is grounded in cognitive and neurobiological understandings of trauma, particularly how trauma-related memories are reactivated by environmental cues. According to Ehlers and Clark’s (2000) cognitive model of PTSD, distress persists when individuals misinterpret trauma reminders as indicators of current threat. This happens through stimulus generalization, where neutral or safe cues that resemble elements of the traumatic event evoke intense emotional responses.
Stimulus discrimination addresses this process by helping clients systematically attend to the differences between past trauma cues and the current environment. By contrasting sensory information across modalities — what they see, hear, smell, feel, and even their internal bodily states — clients can reappraise present experiences as safe rather than threatening.
This approach is consistent with dual representation theory (Brewin, Dalgleish, & Joseph, 1996), which posits that trauma memories are stored in two systems: verbally accessible memory (VAM) and situationally accessible memory (SAM). Triggers often activate SAM, resulting in vivid and intrusive re-experiencing. Stimulus discrimination supports access to VAM, allowing clients to contextualize their memories and distinguish between “then” and “now”.
Neuroscience research also supports this framework. Findings from studies on fear extinction and context processing (e.g. Milad et al., 2007) suggest that the ability to recognize contextual differences is central to reducing conditioned fear responses. Stimulus discrimination may activate the prefrontal cortex, facilitating top-down regulation of the amygdala’s fear responses, and helping consolidate learning that the present is safe.
