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Humans have the amazing ability to recreate events in the smallest detail in their mind’s eye. Over 50 years ago, Donald Hebb and Ulrich Neisser, the forefathers of cognitive psychology, theorized that eye movement is critical to our ability to do so. They pointed out that we move our eyes not only to receive sensory visual input, but also to recall information stored in memory. Our latest study provides the only academic evidence for their theory to date.
It could help research in everything from human biology to robotics. For example, it could shed new light on the connection between eye movements, mental images, and dreams.
We can only process information from a small part of our visual field at a time. We overcome this limitation by constantly shifting our focus of attention through eye movements. Eye movements unfold in sequences of fixations and saccades. Fixations, occurring three to four times per second, are the brief moments of concentration that allow us to sample visual information, and saccades are the rapid movements from one fixation point to another.
Although only a limited amount of information can be processed at each fixation point, a sequence of eye movements connects visual details (e.g. faces and objects). This allows us to encode a memory of what we can see as a whole. Our visual scanning of the world – through our eye movements – determines the content of the memories our brain stores.
A journey into the past
In our study, 60 participants were shown images of scenes and objects, e.g. B. A cityscape and vegetables on a kitchen counter. After a short pause, they were asked to retrieve the images as accurately as possible while looking at a blank screen. They rated the quality of their memory 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 participants’ scan paths and their eye-movement sequences both when they viewed the images and when they recalled them.
We showed that scanning pathways during memory retrieval were associated with the quality of participants’ recall. When the participants’ scan paths most closely mimicked how their eyes moved as they viewed the original image, they were at their best during the recall. Our results demonstrate that actually reproducing a sequence of eye movements enhances memory reconstruction.
We analyzed various features of the course of the participants’ scan paths over space and time – such as the order of fixations and the direction of saccades. Some scan path characteristics were more important than others depending on the type of storage sought. For example, the direction of eye movement was more important when remembering the details of how pastries were arranged side by side on a table than when remembering the shape of a rock formation. Such differences can be attributed to different memory requirements. Reconstructing the precise arrangement of pastries is more challenging than reconstructing the rough arrangement of a rock formation.
Episodic memory allows us to mentally travel in time to relive past experiences. Previous research has shown that we tend to reproduce gaze patterns of the original event we are trying to recall and that gaze positions during memory retrieval have important consequences for what you remember. These results all relate to static gaze, not eye movement.
Donald and Ulrich’s 1968 theory was that eye movements are used to organize and assemble ‘partial images’ into an overall image that is visualized during episodic recall. Our study showed that the way scan paths unfold over time is critical to recreating experiences in our mind’s eye.
One step forward
Findings could be important for cognitive neuroscience and human biology research, and in fields as diverse as computing and image processing, robotics, workplace design, and clinical psychology. This is because they provide behavioral evidence for a critical link between eye movements and cognitive processing that can be leveraged for treatments such as brain injury rehabilitation. For example, Eye Movement Desensitization and Reprocessing (EMDR) is an established psychotherapeutic treatment for post-traumatic stress disorder (PTSD).
In this therapy, the patient focuses on the trauma and performs bilateral eye movements, which is associated with a reduction in the vividness and emotion associated with the memory of the trauma. But the underlying mechanisms of therapy are not yet well understood. Our study shows a direct link between eye movements and human memory systems that could provide a key piece of the puzzle.
This article was republished by The Conversation under a Creative Commons license. Read the original article.
