HMN 2025: How Tracking anticipatory gaze offers new way to assess memory in silent patients

To assess and study human memory, psychologists have so far primarily used tasks that require people to verbally recall objects they previously saw in images, past life events or other types of information. While these tasks are widely employed by researchers, they are not applicable to individuals with a reduced verbal ability or those who cannot communicate at all, such as young children, some people diagnosed with Alzheimer’s disease and patients who have lost the ability to speak following brain injuries.

A team of neuroscientists and medical researchers in the lab of Prof. Yuval Nir at Tel Aviv University and the Tel Aviv Sourasky Medical Center recently discovered that gazing at a specific location in space before an event witnessed before happens (i.e., anticipatory gaze) could be a nonverbal indication that a person remembers something. This important finding, published in Communications Psychology, could open valuable possibilities for the development of tests to assess the memory of individuals who are unable to speak or have limited verbal abilities.

“Our research had two motivations,” Dr. Flavio Schmidig, first author of the paper, told Medical Xpress. “First, traditionally, if we probe episodic memories in humans, we ask whether you remember this or that. This is very different from how we remember most of the time in our daily lives. Namely when memory passively pops into our heads.

“Thus, we wanted to stop asking people to remember as a means of studying memory. Second, we set out to measure memory without the need to speak. This would allow us to examine memory in infants, brain injury victims or severe Alzheimer’s patients.”

As part of their recent study, Schmidig and his colleagues thus set out to develop a new memory paradigm that could be used to test people’s memory without the need for them to answer questions verbally. The paradigm they proposed entails tracking people’s gaze (i.e., where they direct their eyes) while they are completing a memory task.

“In our study, 145 healthy subjects watched tailor-made animated videos twice,” explained Schmidig, who led the study together with Dr. Daniel Yamin and Dr. Omer Sharon. “The videos included a surprising event—such as a dolphin jumping out of the water. Tracking the subjects’ eye movements through two separate viewings of the same films, we found that during the second viewing subjects shifted their gaze toward the area where the surprising event was about to occur.”

To determine the extent to which their paradigm actually assessed people’s short-term memory function, the researchers compared the eye-movement data they collected during their experiments with the verbal responses provided by participants during a conventional memory task. Notably, they found that anticipatory gaze captured people’s memory of surprising events in videos similarly to verbal answers and independently of their ability to speak.

“Our paradigm measures anticipatory gaze completely independent of language,” said Schmidig. “With only a camera, we were able to capture the extent someone remembers, in a passive way, closest to our everyday life. Using AI machine learning techniques, it is possible to infer automatically, from just a few seconds of eye tracking data, whether someone has seen a video before and formed a memory of it. This enables us to understand how memory functions in places and groups that were previously inaccessible.”

The work by Schmidig and his colleagues could soon pave the way for new neuroscience and psychology research focusing on the memory functions of young children who have not yet learned to speak or adults who have lost their verbal abilities due to brain injuries or neurodegenerative diseases. This research could in turn yield very interesting findings, which might improve the present understanding of human cognitive capabilities in early childhood or of specific medical conditions linked to memory deficits.

“Gaze direction can be simply detected by the camera of a laptop or smartphone as the subject views a video—with no need for large, sophisticated equipment,” added Schmidig. “The method we developed has the potential for identifying memories even in situations that have so far been out of reach for us as scientists and clinicians.”

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