By Duncan Dodson
When I go home and reminisce with family about road trips we took or embarrassing moments they facilitated, eventually we’ll disagree on “what actually happened.” We’re all so certain—our memories unfold vividly yet contrarily. It’s clear the past can be subjective, but why is this so?
As part of Duke University’s Brain Awareness Week, I went to a talk at Fullsteam Brewery on imagining alternate realities by Dr. Felipe De Brigard, Assistant Professor of Philosophy and member of Center for Cognitive Neuroscience. De Brigard began by discussing studies of patients with hippocampal atrophy (as in amnesia, PTSD, and severe depression) struggling to place themselves in both the future and the past. Their impoverished answers contrast with those of healthy controls, suggesting a link between areas of the brain accessed for recalling the past and picturing the future.
De Brigard buttressed this by displaying fMRI neural images of parts of the brain used when imagining future events and evoking memories. These parts encompass the default network: a system of functions and firings executed when the brain is not engaged in a specific task. Evidence shows the default network allows engagement in “mental time travel” or the projection of oneself into the future or onto the singular, objective past. This assumption leads to temporal asymmetry: only one past exists with which the imagination can corroborate yet it can visualize limitless possibilities.
De Brigard challenged this view: what if the default network works in both directions? He argues that the parts of the brain used for imagining possible futures also allow us to conceive potential outcomes in our past that did not occur, the process of counterfactual thinking. He has found that when contemplating an alternative reality considered likely to have occurred, the brain behaves as if it were remembering. Memory is not haphazard reproduction but probabilistic reconstruction — our memory is constantly rebuilding the past with both fact and what are likely facts, and frequently the distinction is blurred.
“Perhaps we should cut Brian Williams a little slack?” De Brigard chuckled. Ample evidence shows that engagement in especially rich and detailed counterfactual thinking can increase the probability of constructing — and believing the authenticity of — false memories.
More intriguing than pardoning Williams are potential contributions to treatment of anxiety, depression, and PTSD. A common debilitating trigger among these disorders is repetitive counterfactual thinking, “I shouldn’t have said that, I shouldn’t have said that.” Perhaps with further study on the default network and its relationship to autobiographical contemplations, neuroscientists might develop tools to alter the pathways or functionality of the default network.
As for my family, they have some major counterfactual thinking patterns to alter; my memory is immaculate.