Why We Forget Trauma

It’s nearly impossible to determine the exact reason why someone may forget parts—or the entirety—of a traumatic experience. But we can find some reassurance in identifying the various factors at play when it comes to trauma, encoding memory, and memory retrieval & recall.

1. We Never Encode Everything About Any Experience

We never encode every detail of any experience. Even in ordinary situations, our memories are selective: we take in some aspects of what’s happening and ignore countless others. Memory has limitations built into it, and this means that all memories—even happy ones—are partial by nature. Trauma does not break a normally complete system; it simply adds stress to a system that is already highly selective. So when someone “forgets” parts of a traumatic event, it isn’t evidence of repression or deception. It’s simply a reflection of how memory functions for everyone, all the time. Trauma highlights this truth more dramatically because the circumstances make the brain even more selective about what it can encode.

2. Attention Determines What Gets Stored: Central vs. Peripheral Details

Memory encoding depends heavily on where a person’s attention goes in a given moment. The details we focus on and attach significance to become “central details,” and these are the ones likely to be stored. Everything else becomes “peripheral” and may never enter memory in the first place. During trauma, this distinction becomes even sharper. A child or adult in danger may focus intensely on something small or seemingly irrelevant—a spot on the wall, the pattern of ceiling tiles, a tree branch, the clouds. Meanwhile, they may give almost no attention to what is happening to their body or to the actions of the perpetrator. The brain encodes what it pays attention to, not what outsiders believe should have mattered most. This natural attentional narrowing is a major reason trauma memories often appear fragmented or incomplete.

3. Trauma Narrows Attention to What Feels Safe or Striking

Under threat, the mind narrows to whatever feels safest, most soothing, or most striking in the moment. This is a survival strategy: focusing on something stable or less threatening can help a person cope with overwhelming fear. As a result, the brain may encode vivid fragments of a sensory anchor—like sunlight, a noise, a pattern, or a smell—while barely encoding the traumatic actions occurring at the same time. This is not a failure of memory; it is an adaptation. The experience becomes encoded as intense but disjointed sensory impressions rather than a coherent, chronological narrative. To an outside observer, this fragmentation may seem odd, but it simply reflects what the brain chose as its “central details” under stress.

4. Traumatic Stress Disrupts the Encoding of Experience

High levels of fear and threat alter how the brain’s memory systems operate. When someone is terrified, hormones and stress chemicals change the functioning of structures like the hippocampus, which is responsible for forming contextual and chronological memories. This means the brain may store isolated sensory fragments but fail to encode the order of events, the transitions, or the surrounding context. The result is a memory that contains pieces but lacks the connective tissue that makes a story feel complete. Trauma survivors often describe this as having “snapshots” instead of a full movie. This disruption happens at the encoding stage—not later—and explains why people cannot recall sequences or “fill in the blanks,” no matter how hard they try.

5. Dissociation or “Checking Out” Impairs Memory Formation

Many survivors dissociate during trauma, meaning their awareness disconnects from what is happening in their body or from the surrounding environment. This psychological distancing can protect a person emotionally, but it reduces the brain’s ability to encode what is happening. When someone is dissociated, their sensory input is reduced, their ability to process information changes, and their normal conscious awareness is altered. As a result, the memories that do get stored may be limited, distorted, or purely sensory. A person may vividly remember the wallpaper, the sound of the wind, or a smell, but have little or no memory of sensations in their body or of what the perpetrator was doing. Dissociation therefore contributes significantly to the fragmented quality of many trauma memories.

6. Sensory Fragments Are Encoded, but Not the Narrative

Episodic memory consists of sensory fragments—images, sounds, bodily sensations—while narrative memory is the ability to put those fragments into a coherent story. During trauma, the brain often encodes episodic fragments but struggles to create a narrative structure. This is why people may initially have powerful sensory recollections—like a smell, a sound, or a bodily feeling—without being able to explain the meaning or sequence behind them. Over time, especially in safe contexts like therapy, survivors may integrate these fragments into a narrative, but the underlying fragmentation remains. What gets encoded determines what can later be woven into a story.

7. Body Memories and Somatic Sensations Surface When Narrative Memory Is Absent

What people sometimes call “body memories” or “somatic memories” are physical sensations that arise from deep brain systems involved in processing fear, pain, shame, and threat. These sensations can be incredibly vivid—tightness in the throat, nausea, numbness, shaking, disgust—yet they may not initially be recognized as memories. Although these experiences are felt in the body, the memories themselves live in the brain regions that process bodily sensation and generate physiological responses. During trauma, especially childhood trauma, the body often “remembers” far more clearly than the narrative mind does. This leads to situations where a person has intense emotional or bodily reactions long before they understand the event those sensations are connected to.

8. Some Memories Are Stored but Not Immediately Accessible

Even when details are encoded, they may not be retrieved right away. Memory is not an automatic system; what we store and what we recall are different processes. People may have encoded certain sensory impressions or central details during trauma but may not access them until they encounter specific triggers, enter therapy, or learn that their reactions have meaning. Survivors often connect the dots over time—recognizing that a bodily response, a fear, or a sensory flash is actually linked to the trauma. This is not “recovering” a memory in the sense of manufacturing it; it is recognizing a previously implicit memory as part of one’s history. The delay in retrieval contributes to the sense of having forgotten or having only partial memory of what happened.

9. Children Encode Trauma Differently

For children, the ability to form narrative memories is still developing, and their attention may gravitate toward environmental details rather than their body or the actions happening to them. A child might remember the pattern of leaves above them, the sound of a creek, or the color of a blanket, but encode little about the abuse itself. Early childhood trauma—especially pre-verbal trauma—is often stored primarily as sensations, emotional states, and implicit memories rather than verbal or narrative memories. This developmental reality explains why many adult survivors of childhood abuse have sensory or somatic memory traces without clear images or stories attached. The memory was never encoded in narrative form to begin with.

10. Trauma Memories Are Inherently Fragmented Because of How the Brain Encodes Experience

Taken together, these factors show that fragmentation is not an anomaly—it is the expected outcome of how human memory works under threat. Trauma does not produce a “faulty” memory system; it produces a memory system doing exactly what it is designed to do in danger: prioritize attention to certain details, protect the person emotionally, and reduce the load on cognitive processing when overwhelmed. The result is a collection of vivid fragments, powerful bodily sensations, and emotional imprints, with missing sequences and gaps that cannot be filled in later. This is not forgetting in the everyday sense. It is the natural consequence of how the brain encodes experience under conditions of fear, dissociation, and survival.

Looking to Learn More?

Featured in Paper Birds, Dr. Jim Hopper is a nationally recognized expert on psychological trauma. On his website, you can find a wealth of information—from research studies to free resources—about trauma and the brain, especially as it relates to the nature of traumatic memories. Click on the button below to view.