(ORDO NEWS) — A new study has provided evidence supporting the role of eye movements in recreating events in consciousness.
Humans have an amazing ability to recreate events in their minds in great detail. More than 50 years ago, Donald Hebb and Ulrich Neisser, the founders of cognitive psychology, suggested that eye movements play an important role in our ability to do this.
They noted that we move our eyes not only to receive sensory visual input, but also to recall stored information. Our recent study provides the only academic evidence for their theory to date.
It can help in research in all areas – from human biology to robotics. For example, it can shed new light on the relationship between eye movements, mental images, and dreams.
At the same time, we can only process information from a small part of our visual field. We overcome this limitation by constantly shifting the focus of attention through eye movements.
Eye movements unfold in a sequence of fixations and saccades. Fixations occur three to four times per second and are brief moments of focus that allow us to select visual information, while saccades are fast movements from one fixation point to another.
Although only a limited amount of information can be processed at each fixation point, the sequence of eye movements ties together visual details (such as faces and objects). This allows us to encode the memory of what we see as a whole. Our visual sampling of the world – through eye movements – determines the content of the memories our brains store.
Journey down the lanes of memory
In our study, 60 participants were shown pictures of scenes and objects, such as a cityscape and vegetables on a kitchen table. After a short break, they were asked to recall these images in as much detail as they could while looking at a blank screen.
They rated the quality of their memories and were asked to choose the correct image from a set of very similar images. Using state-of-the-art eye-tracking techniques, we measured the participants’ scan patterns, the sequence of eye movements, both when viewing images and recalling them.
We have shown that scan patterns during memory recovery are related to the quality of memorization. When the participants’ scans most closely matched their eye movements when viewing the original image, they performed best during recall.
Our results suggest that actually reproducing the sequence of eye movements contributes to memory retrieval.
We analyzed various features of how participants’ scanning trajectories evolved in space and time, such as the order of fixations and the direction of saccades. Some characteristics of the scanpath were more important than others, depending on the nature of the memory sought.
For example, the direction of eye movement was more important in remembering the details of how cakes were placed next to each other on a table than in remembering the shape of a rock.
Such differences can be explained by different memory requirements. Restoring the exact location of the cakes requires more effort than restoring a rough plan of a rock formation.
Episodic memory allows us to mentally travel through time to relive past experiences. Previous research has shown that we tend to recall gaze patterns from the initial event we are trying to recall, and that the location of the gaze during memory retrieval has important implications for what you remember. All these conclusions refer to a static gaze, and not to eye movements.
Donald and Ulrich’s 1968 theory was that eye movements are used to organize and assemble “part images” into a coherent image that is visualized during episodic memory. Our research has shown that how scanpaths unfold over time is critical to recreating impressions in our minds.
The findings may be important for research in cognitive neuroscience and human biology, as well as in fields as diverse as computing and imaging, robotics, workplace design, and clinical psychology.
This is because they provide behavioral evidence for the critical link between eye movements and cognition that could be used for treatment, such as rehabilitation after brain injury. For example, eye movement desensitization and processing (EMDR) is a well-established psychotherapy for post-traumatic stress disorder (PTSD).
During this therapy, the patient focuses on the trauma and makes bilateral eye movements, which leads to a decrease in the vividness and emotionality of memories of the trauma.
However, the mechanisms underlying this therapy are not yet well understood. Our study shows a direct link between eye movements and human memory systems, which could be an important piece of the puzzle.”
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