Unseen memories

Can you vividly recall the sights, sounds and smells of your 5th birthday party? 

Take some time to “bring yourself there”….

What do you feel? How do you experience that memory? 

Most visualizers describe a form of “mental time travel” where they experience multisensory “videos” of those childhood memories. For others, trying to re-experience old memories feels more like reading entries from a personal journal.

Severely Deficient Autobiographical Memory, or SDAM for short, is a condition coined by Dr. Brian Levine, a senior scientist at the Rotman Research Institute. It refers to the inability to relive episodic memories in rich multisensory detail.

Those with SDAM can recall facts about past experiences, but the mental “videos” lack vividness and sensory richness – or simply don’t exist.

This condition often co-occurs with aphantasia (inability to visualize). Both impact how information is processed and recollected.

But here’s the intriguing part – many with SDAM don’t realize their memory differs from the general population until well into adulthood. Just as aphantasic artists may not realize their creative process is unique, those with SDAM assume everyone experiences memories in the same subjective way.

It’s almost like two parallel worlds are existing side by side. One where memories blaze with vivid colors, sounds, and sensations. And another where recollections are more like recounting stories, facts and trivia from a personal journal.

Here’s an excerpt from Dr. Adam Zeman’s latest paper

On a range of standard experimental measures of memory (short- and long-term, verbal and visual), people with aphantasia perform normally or show, at most, mild to moderate impairment. Average IQ is, if anything, marginally higher in people with aphantasia than hyperphantasia. However, one aspect of memory, that is typically neglected in standard assessments, is more markedly reduced in aphantasia, as suggested by anecdotal reports. Both subjective and objective measures of the richness of autobiographical memory are reduced in aphantasia but increased in hyperphantasia.

SDAM reveals just how diverse human experience can be, even for something as fundamental as revisiting our personal pasts.