Moreover, this method can be used to measure memory in subjects who cannot speak, such as infants, patients with brain injuries, or even animals. Tracking the subjects’ eye movements through two separate viewings of the same films, the researchers found that during the second viewing subjects shifted their gaze toward the area where the surprising event was about to occur. “The study proves that tracking eye movements can be an excellent alternative to verbal questions such as ‘Do you remember this?’,” Yamin says. “In a series of experiments, we demonstrated that gaze direction is a very sensitive gauge of memory. Even when subjects said they didn’t remember, their gaze direction showed they did.