credit: Lotus Head from Johannesburg, Gauteng, South Africa; http://creativecommons.org/licenses/by-sa/3.0/deed.en
Trying to remember how you arranged last year’s Christmas ornaments on the tree? It turns out that blankly gazing at your empty tree could help. According to a new study, when we look even at an empty space, it cues our brain to remember the orientation of objects that previously occupied that space. Our eye movements thus are key to episodic memory, allowing us to reconstruct imagery from the past.
“Episodic memory allows us to travel back in time to relive previous events from a first-person perspective,” says Mikael Johansson of Lund University in Sweden. “Remembering depends on the interaction between retrieval cues and stored memories.” The more similar the cues are when we try to retrieve the memory as when we first saw it, the more likely we are to remember something.
Johansson, who studies the factors that influence the accessibility of stored memories, teamed up with Roger Johansson, who studies the interplay between eye movements and visual imagery. They wanted to explore the effects on memory retrieval of where and how our eyes look, even if the relevant visual information is no longer available in the immediate surrounding.
Study participants had to remember the orientation of 24 different objects; gazing at the empty space an object occupied aided its memory retrieval
The researchers first asked participants to study 24 objects set up in quadrants on a computer screen. The screen then went blank, and the researchers then guided where and how participants looked while they answered questions about the original object arrangement. “Critically, we guided participants to look at positions that either corresponded or didn’t correspond with the original locations of the to-be-retrieved objects,” Johansson says. They used an eye tracker to record participants’ gaze.
As published in Psychological Science, they found that participants were better able to remember spatial properties of objects when they viewed an empty space that corresponded to the original location of the object, as opposed to a different location or just freely viewing the screen. “Although we were optimistic that our experiment would offer novel data,” Johansson says, “we were pleasantly surprised that our results provided clear evidence of a functional role of eye movements and that retrieval performance can either become facilitated or perturbed depending on where you look.”
The experiment showed that where we look affects memory for spatial relations between objects more than memory of intrinsic object features. “We believe that the role of eye movements is similar during episodic remembering as when we look at things in the ‘real world’ – we need to move our eyes to specific locations to explore how different features relate to each other,” Johansson says. “This behavior is not as important when only one feature is in focus.”
One novel aspect to the experiment was in its use of several concurrent objects. “This introduced competition and potential interference between objects,” Johansson says. “Most previous research had only investigated memory for single objects.”
The impact of our eye movements on memory all comes down to context, he says. “It is not the looking at any ‘nothing’ that facilitates remembering, but the looking at a particular ‘nothing,’ the location that spatially overlaps with the to-be-recalled object.”
Johansson and colleagues are now working to combine eye-tracking with electrophysiological measures of brain activity. They want to tease apart the factors that affect gaze behavior, as well as to identify its neural underpinnings.
-Lisa M.P. Munoz
