Recent research on impact of trauma on memory

Dr Cathy Kezelman, AM, President of the Blue Knot Foundation National Centre of Excellence for Complex Trauma, discusses recent research into memory and how misconceptions about memory are common. An understanding of the impacts of overwhelming stress in relation to memory is essential for due process, she writes. Dr Kezelman presented a seminar on this topic for Legalwise Seminars. Dr Cathy Kezelman


Misconceptions about memory are common and, they can have costly repercussions for individuals as well as for systems of justice. As with research into the brain – with which it overlaps – research into the workings of memory is rapidly expanding. It is a subject which raises many critical questions. Yet it is often confusing, particularly in relation to trauma. For this reason it is very important to clarify what the most recent research about memory tells us.

Neuroscientific and other research confirms that memory is not a single entity.[1] Rather it comprises different types of memory which do not relate solely to conscious recall. The different types of memory are associated with complex neural networks and are stored in different areas of the brain. This has major implications not only for our understanding of memory, but for our understanding of traumatic memory, the ways it is expressed, and ways it can be resolved. The nature of memory, in relation to trauma, is very topical right now, as cases of historical child sexual offences highlighted by the Royal Commission into Institutional Child Sexual Abuse are tried within our courts.

There are two main types of memory: explicit[2] (which is conscious and can be verbalised) and implicit (which is largely unconscious and not expressed in words). Whenever we consider memory, we should ask the question: ‘what type of memory?’  Consciously recalling meeting our partner’s parents or items on a shopping list are examples of explicit memory. Examples of an implicit memory are a sense of familiarity when we smell a particular fragrance, and our ability to perform certain tasks such as making our usual breakfast.  There are a number of different subcategories of implicit memory[3].

Conscious, explicit memory is central to the recollection of facts and events, and to the exchange of information.[4] Legal professionals tend to overemphasise explicit memory at the expense of implicit memory. Traumatic memories are an intense devastating form of implicit memory. The pleasant implicit memory of a happy summer’s day – elicited by the smell of freshly mown grass – is vastly different from a traumatic implicit memory of a person who was assaulted in a field of freshly cut grass. Such trauma `triggers’ may seem inconsequential to people who don’t experience them. But they are often very alive in the present for the traumatised person who remains vulnerable as long as the trauma remains unresolved[i].

The part of the brain called the hippocampus is central to encoding memory and to conscious recall.[5] A traumatic experience which is so overwhelming that our nervous system can’t process it impedes the functioning of the hippocampus. The experience is `split off’ into fragments which become implicit memory and are stored in the body. These implicit memories can be activated by ‘triggers’ later on, often many years later. These triggers stimulate one or more of our senses and remind our body of prior traumatic events which couldn’t be processed at the time e.g. the sound of a car backfiring triggering former soldiers.

In relation to experience of trauma, not being able to recall an event/s consciously (while implicit memory remains stored in the body) can have a survival value[6]. This applies particularly with child abuse because children are dependent on their adult caregivers and must attach to them to survive. It is well documented that children traumatised by adult caregivers will often lack conscious recollection of the trauma. The younger the child and the more severe the trauma, the greater the likelihood that they will lack conscious recall of it.

`Recovered’ memory (i.e. delayed conscious recall of traumatic experience) is a common feature of different types of trauma and does not relate solely to child sexual abuse.[7] Neither explicit nor implicit memory is infallible, and studies show that `recovered’ memory is no more or less reliable or unreliable than continuous, explicit memory.[8] It is possible for traumatic memory to be consciously recalled, often years after the overwhelming experience/s, via a `trigger’ which elicits a sensory response.

This information is especially critical for legal and justice professionals, because an understanding of the impacts of overwhelming stress in relation to memory is central for due process.


Dr Cathy Kezelman, AM, is a medical practitioner, President of the Blue Knot Foundation – National Centre of Excellence for Complex Trauma; prior member of Independent Advisory Council on Redress; member of the Mental Health Community Advisory Council (NSW), member of NSW Standing Committee of Child Safety. Cathy worked in medical practice for 20 years, mostly as a GP.  Under her stewardship over 15 years, Blue Knot Foundation has grown from a peer support organisation to a leading national organisation combining a prominent consumer voice with that of researchers, academics and clinicians advocating for socio-political change  and informed responsiveness to complex trauma. She is a prominent voice in the media and at conferences, as well as author of a memoir chronicling her journey of recovery from child sexual abuse: Innocence Revisited- a tale in parts. She is co-author of multiple publications including the seminal Blue Knot Foundation document – Practice Guidelines for Treatment of Complex trauma and Trauma Informed Care and Service Delivery and Trauma and the Law – Applying Trauma-informed Practice to Legal and Judicial Contexts. On Australia Day 2015 Cathy was awarded an AM “for significant service to community health as a supporter and advocate for survivors of child abuse”. Contact Cathy at or connect via LinkedIn .

You can also connect with the Blue Knot Foundation via Facebook , Twitter , and LinkedIn . Visit the Blue Knot Foundation for more information on its publications, such as The Truth of Memory and the Memory of Truth: Different Types of Memory and the Significance for Trauma, and for details on its training program for the legal and justice sectors.


[1] James A, Chu, ref. Polsten, Nadel, & Schacter , 1991, (2011) Rebuilding Shattered Lives, New Jersey: John Wiley.

[2] Henry Roediger et al. (2017) `A Typology of Memory Terms’, in John Byrne, ed. Learning and Memory Academic Press, Oxford.

[3] Levine, P. (2015) Trauma and Memory: Brain and Body in a Search for the Living Past. Berkeley, CA: North Atlantic Books.

[4] Roediger, H. et al. (2017) `A Typology of Memory Terms’, in John Byrne, ed. Learning and Memory, Academic Press, Oxford.

[5] Daniel J. Siegel. (2012) Pocket Guide to Interpersonal Neurobiology Norton, New York.

[6] Freyd, J. & Birrell, P. (2013) Blind to Betrayal: How We Fool Ourselves We’re Not Being Fooled. New Jersey: Wiley & Sons.

[7] Barlow, M.R., Pezdek, K. & Blandon-Gitlin, K. (2017) `Trauma and Memory’, ch.16 in Gold, S.N., ed. APA Handbook of Trauma Psychology: Foundations in Knowledge. American Psychological Association, pp.307-331.

[8] Dalenberg, C. (2006) `Recovered Memory and the Daubert Criteria: Recovered Memory as professionally tested, peer reviewed, and accepted In the relevant scientific community’, Trauma, Violence, and Abuse, 7, pp.274-310.