Like Sun-Faded Photographs, Memories Lose Vivid Details

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"Kodachrome gives us those nice bright colors. Gives us the greens of summer. Makes you think all the world's a sunny day, oh yeah. And everything looks worse in black and white." —Paul Simon, "Kodachrome" (1973)

When I reminisce about Memorial Day Weekends of yesteryear, most of my memories have a fuzziness that mirrors the haziness of sun-faded photos. The "nice bright colors" of my vintage Kodachrome photographs from summer vacations in the 1970s have faded, much like my childhood memories of that bygone era are less vibrant now.

New research suggests that much like analog-era photos get washed out and lose perceptual details over time, vivid memories lose their feature-specific clarity through a process of "semantization" or repeated remembering that only focuses on a memory's core elements.

This study (Lifanov et al., 2021) into how memories fade over time and how frequently recalling the same memory may reinforce that memory's central "gist" was published on May 26 in the journal Nature Communications.

The Semanticization of a Memory and Recalling It Repeatedly Over Time Preserves the Memory's "Gist" but Not Its Details

"Many memory theories assume that over time, and as people retell their stories, they tend to forget the surface details but retain the meaningful, semantic content of an event," first author Julia Lifanov of the University of Birmingham said in a news release.

"Imagine reminiscing about a pre-COVID dinner with a friend," she added. "You realize that you cannot recall the table décor but know exactly what you ordered; or you remember the conversation with the bartender, but not the color of his shirt. Memory experts call this phenomenon 'semanticization.'"

For their recent study into the semanticization of memories over time, Livanov and her UK-based colleagues created a series of experiments that measured changes in feature-specific "perceptual only" memory recall versus "conceptual only" recall.

Fuzzy Details and "Gistification" Go Hand-in-Hand

This study suggests that if a specific memory is recalled frequently that it boosts what the researchers call the "gistification" of a memory. Preserving the "gist" of a semantic memory seems to come at the expense of being able to recall a memory's feature-specific details, which tend to get blurrier over time.

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"The pattern towards recollection of meaningful semantic elements we demonstrate in this study indicates that memories are biased towards meaningful content in the first place—and we have shown in previous studies that this bias is clearly reflected in brain signals too," senior author Maria Wimber of the University of Glasgow noted. "Our memories change with time and use; that is a good and adaptive thing. We want our memories to retain the information that is most likely to be useful in the future."

"We keep this love in a photograph. We made these memories for ourselves. And time's forever frozen, still. So you can keep me inside the pocket of your ripped jeans." —Ed Sheeran, "Photograph" (2015)

Even though digital photos never fade, our memories are not a digitized JPEG file of the past that is "forever frozen, still." The latest (2021) research suggests that as autobiographical memories evolve over time, the gist of meaningful semantic information is better preserved than perceptual details, which tend to fade like details on an old sun-bleached photographic image.

"In summary, using feature-specific probes, we provide evidence for the semanticization of memories over time and specifically with repeated remembering," the authors conclude. "Our main results are consistent with a framework where the natural prioritization of conceptual information during repeated retrieval has a lasting effect on what is being retained over time."

Lifanov et al. speculate that this field of research could someday help patients with post-traumatic stress disorder. It's possible that a maladaptive form of "gistification" may cause people with PTSD to over-generalize traumatic memories from their past instead of focusing on the feature-specific perceptual details of novel situations.