If you're driving home for Christmas (insert Chris Rea earworm here) - and by that I mean the old family home - you're likely to be experiencing a familiar mix of excited anticipation and faint dread of being trapped in close quarters with relatives. There's nothing like Christmas for mental time travel triggered by family traditions and well-worn arguments.
Author
- Jane Aspell
Professor of Cognitive Neuroscience, Faculty of Science and Engineering, Anglia Ruskin University
You might also have the sort of family, like mine, which often insists on perceiving and treating you as you were 40-plus years ago. Although I'm closer than I'd like to 50, my father still voices concerns about me crossing roads, "wrapping up warm" and leaving electric plugs switched on. I will forever be his little girl.
Since our identity is in part created by how those around us see us and behave towards us , the festive season can temporarily cause us to regress to a past, childish version of our self - and this isn't always welcome. But I'd like to suggest there is a silver lining of opportunity here though: the chance to gain access to forgotten memories.
As a professor of cognitive neuroscience, I've been lucky enough to be able to test this idea with colleagues in my lab . In particular, we wanted to scientifically investigate whether people can recall more detailed childhood memories if they can "reinhabit" the body they had as a child.
I think it makes intuitive sense that this might work: the body I had as a child was very different to the one I currently occupy in middle age, and it seems reasonable to suppose that a (usually overlooked) aspect of our childhood memories - indeed of all memories - is the kind of body we used to have.
Our bodily experience is so ever-present that we usually don't even notice it unless we are in some pain or discomfort. But there is not a minute of your life when your brain does not receive a mass of sensory input from and about your body: the sight of your hands in your peripheral vision, the sound of your footsteps and breathing, the beating of your heart, the contractions of your stomach and the tension in your muscles. Since the body is a big part of what we perceive in every moment, its varying form (as we age and change) should also be encoded in our memories.
As time passes, remote memories can dim, and some may even seem to disappear. But in most cases, they are never really "gone" from the brain - we just need the right trigger to reactivate them and bring them back into our consciousness.
A magic mental jigsaw
Memory is a bit like a magic mental jigsaw. Once you get hold of one jigsaw piece, a linking piece can suddenly pop into your mind. Our idea was to give participants in our lab the piece that enables them to re-experience their childhood bodies, in the hope that this could enable better access to memories that were laid down when they occupied those younger bodies.
We did this by causing our participants to experience a body illusion known as the "enfacement illusion". We asked them to sit facing a computer screen with an attached webcam. On the screen, they could see a live video of their own face as filmed by the camera, but for half the participants there was a twist: the video had been distorted by a popular Snapchat app filter . Instead of seeing a video of their face as it currently looked, they saw their face morphed into a childlike version: their face resembled how it looked when they were a child.
We instructed them to move their head from side to side for 90 seconds while keeping their eyes fixed on the screen. This movement was important, as it provided crucial information to their brains about the self-relatedness of the image they saw.
Given that the face on screen moved exactly in time with their own face, this tricked the brain that the face on screen was really theirs. It was as though the participant was looking into a mirror but seeing the face they had as a child looking back at them. A different group of participants watched an undistorted video of their own face as they made the same movements.
To test whether this brief illusion has effects on memory recall, immediately after the illusion the participants took part in an "autobiographical memory interview". The lead researcher - my former PhD student Utkarsh Gupta - followed a strict protocol to ask them a series of questions that would result in them describing an individual memory from their childhood in as much detail as possible. These interviews were recorded, and the transcripts were later numerically rated for specificity and detail by two researchers who were blind to the group that each participant had been assigned to.
Although the illusion was very brief, we found a significant difference between the memories described by participants in each group. As we had predicted, those who "re-embodied" their childlike faces were able to recall significantly more detailed memories than the participants who viewed their current face.
Our study was therefore able to show that body, self and memory interact, as indeed they must, in order for our brains to create our experience of personal identity - what makes "me" the person that I am.
Our identity necessarily evolves over time (even though our parents may sometimes have difficulty recognising that). And integrating memories of our past with the present moment is not always easy.
Our memories are not only records of the things that we previously saw, thought, smelt and heard. They are also records of the kind of body that our self used to drive around in. All our past selves are etched into our brains. The ghosts of Christmases past never really melt away.
Jane Aspell receives funding from the Leverhulme Trust and has previously been funded by Versus Arthritis, the Bial Foundation, the British Academy, The Urology Foundation and the Wellcome Trust.
