Couples share a unique form of contagious forgetting, new research suggests

Couples often finish each other’s sentences. New research suggests they may also help edit each other’s memories. A study published in the Quarterly Journal of Experimental Psychology provides evidence that romantic partners synchronize their brain activity during storytelling. This neural alignment leads to a specific type of shared forgetting that does not occur between strangers.

The research indicates that the closeness of a relationship fundamentally alters how two people process information together. When one partner selectively remembers certain details of an event, the other partner tends to forget related but unmentioned details. This phenomenon suggests that memory is not just an individual archive but a collaborative system shaped by social bonds.

Psychologists have long understood that human memory is reconstructive rather than reproductive. When a person tries to recall a specific piece of information, their brain must actively select that target memory. In doing so, the brain suppresses competing memories that might interfere with the retrieval.

For example, if a person tries to remember “Fruit-Orange,” they may temporarily suppress the memory of “Fruit-Banana” to avoid confusion. This process is known as retrieval-induced forgetting. It is a standard mechanism that helps keep cognitive processes efficient and focused.

However, this pruning process is not confined to a single mind. Previous research has identified a phenomenon called socially shared retrieval-induced forgetting. This occurs when a listener experiences the same memory suppression as the speaker.

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If a speaker recalls “Fruit-Orange,” a listener who is paying attention will also involuntarily suppress “Fruit-Banana.” Later, that listener will find it harder to recall “Banana” than if they had never heard the speaker at all. The current study aimed to see if this “contagious” forgetting is stronger between people who love each other.

Huan Zhang, the study’s first author, conducted this research with colleagues at Tianjin Normal University in China. The team posited that romantic partners share a unique cognitive reality. Over time, couples develop aligned patterns of thinking and communicating.

The researchers hypothesized that this deep connection would make partners more susceptible to influencing each other’s memory systems. To test this, they designed two experiments involving heterosexual couples and pairs of strangers.

The first experiment focused on whether the type of memory mattered. The researchers recruited 38 adults forming 19 romantic couples. These participants had been in relationships for at least six months.

The researchers used cue words to trigger autobiographical memories. Some cues prompted “joint” memories, which were events the couple experienced together. Other cues prompted “non-joint” memories, which were private events unknown to the partner.

During the learning phase, participants studied these memories. Then, they entered a retrieval practice phase. One partner acted as the speaker and the other as the listener. The speaker practiced recalling specific details of the memories while the listener simply listened.

Later, both participants performed a final recall test individually. They tried to remember all the details associated with the original cues. This included the items the speaker practiced and the related items the speaker skipped.

The results showed a clear pattern of forgetting. Listeners struggled to recall the unmentioned details related to what the speaker had practiced. This happened for both shared memories and private memories. The connection between the partners seemed to facilitate this effect regardless of the content.

The researchers then expanded the study to include strangers. In a second experiment, they recruited 76 participants. These included 20 romantic couples and 18 pairs of strangers who were introduced just before the test.

To ensure a fair comparison, all pairs used non-joint memories. This eliminated the advantage couples might have from knowing their partner’s past. The procedure remained the same, with one person speaking and the other listening.

The findings revealed a divergence between the groups. Romantic partners again exhibited socially shared retrieval-induced forgetting. When the speaker recalled specific details, the listening partner forgot the related, unmentioned details.

In contrast, the pairs of strangers did not show this effect. The listeners in the stranger group did not experience significant memory suppression. This result differs from some prior studies that found effects among strangers, but it highlights the potential power of intimacy.

The researchers propose that romantic partners have a higher motivation to align their thinking. Listeners in a relationship may simulate the speaker’s retrieval process more intensely. This leads to the same suppression mechanisms triggering in the listener’s brain.

To understand the biology behind this, the team conducted a third experiment using functional near-infrared spectroscopy. This is a non-invasive imaging technique. It uses light to measure blood flow and oxygen levels in the brain.

The researchers focused on the prefrontal cortex. This brain region is associated with executive control and memory regulation. They attached sensors to the foreheads of 38 pairs of participants, comprising both couples and strangers.

The brain imaging data showed higher overall activation in the prefrontal cortex for romantic couples compared to strangers. This suggests that couples engaged more cognitive resources during the collaborative task.

More revealing was the analysis of neural synchronization. The researchers looked at how the brain waves of the speaker and listener matched up over time. They found a high degree of interpersonal neural synchronization in the romantic pairs.

Specifically, the signals in the lateral prefrontal cortex of the listeners synced with those of the speakers. This synchronization was significantly stronger in couples than in stranger pairs. The brains of the partners effectively began to operate in rhythm.

The researchers then looked for a link between this brain activity and the memory test results. They found a statistical correlation. The stronger the neural synchronization between a couple, the more the listener experienced memory forgetting.

This suggests that the synchronization is not just a side effect of being together. It appears to be the mechanism that allows one partner’s memory process to reshape the other’s. The brain data explained about 10 percent of the variation in the forgetting effect.

The authors argue that this synchronization helps couples build a “shared reality.” By aligning what they remember and what they forget, partners maintain a coherent shared view of the world. This comes at the cost of losing some individual details.

There are caveats to these findings. The study participants were Chinese university students. Cultural factors regarding relationships and social influence could play a role. The results might differ in Western cultures where independence is often prioritized over social alignment.

The experimental setup was also artificial. Participants had fixed roles as speakers or listeners. Real conversations are dynamic, with partners swapping roles rapidly. Future research needs to examine these effects in naturalistic settings.

The imaging technique also has limitations. Functional near-infrared spectroscopy only measures the surface of the brain. It cannot reach deeper structures that might be involved in memory. It also has lower spatial resolution than MRI scans.

Despite these limitations, the study offers a new perspective on social cognition. It provides biological evidence that romantic love creates a neural link between partners. This link facilitates the updating and pruning of memories across two brains.

The findings imply that our memories are not entirely our own. Who we spend our time with helps determine what we remember and what we forget. In a romantic relationship, the price of harmony may be the loss of specific unshared details.

Future research aims to explore different types of relationships. It remains to be seen if close friends or family members show similar synchronization. The researchers also hope to see if this effect holds true for emotional memories versus neutral ones.

For now, the data suggests that becoming a couple involves a convergence of minds. This convergence is visible in the blood flow of the prefrontal cortex. It manifests as a synchronized reshaping of the past.

The study, “The role of romantic relationships in socially shared retrieval-induced forgetting: Cognitive and neural evidence,” was authored by Huan Zhang, Yuyao Chang, Shamali Ahati, Jiaying Pu and Tour Liu.