Neuroscience
You've probably noticed how people move their eyes about when in the midst of conversation, often in ways that have absolutely nothing to do with looking at the scene around them. In fact these 'non-visual gaze patterns' also occur when we're on our own, in the complete dark, and even when our eyes are closed. The implication is these eye movements are a result of mental processes that have nothing to do with vision or social factors.
To investigate, Dragana Micic and colleagues recorded the eye movements of 17 female and 12 male participants while they performed two tasks designed to be as similar as possible except for the fact that one required delving into long-term memory and the other didn't. The testing took place in a bare room with the walls draped in white sheets to reduce visual stimulation.
The first task involved the participants sitting on their own in the room, listening to three words then repeating them back after a delay (drawing on short-term or working memory). The second task was the 'remote associates test', which involves delving into long-term memory to identify the one word that matches the meaning of three others (e.g. envy, golf, beans; answer: green). All words were presented out loud, so there was no reading. The participants made far more jerky 'saccadic' eye movements during the latter task, thus suggesting that non-visual eye movements are triggered by long-term memory retrieval.
Two further studies tested whether these eye movements occur more when digging for a less accessible memory and secondly, whether they actually serve a useful function. This was achieved by varying how well the participants learned a word list (thus varying the accessibility of the memories) and, in another experiment, by instructing participants to fixate during a long-term memory retrieval task. These tests revealed that eye movements don't increase when attempting to locate a particularly inaccessible memory, and neither do they play a functional role - participants' memory performance was not impaired when they were instructed to fixate. In the jargon, this suggests that non-visual eye-movements are an epiphenomenon - triggered by long-term memory retrieval but playing no useful part in that activity.
So, why should accessing long-term memory trigger eye movements? Micic's team think the phenomenon is caused by an evolutionary hang-over. By this account, some of the same (evolutionarily older) processes involved in searching a visual scene are co-opted for use when consciously exploring the mind's archives. 'The possibility that spontaneous saccadic eye movements occur despite being non-functional may simply indicate how the addition of higher brain functions does not necessitate the "redesign of the whole brain",' they said.
At first, these new findings seem to contradict another line of research that's previously shown the beneficial role of gaze aversion (looking away from a questioner) when children and adults are working out a solution to maths and memory problems [pdf]. And to contradict the literature showing that wiggling the eyes from side to side can aid memory. Micic thinks the difference here is probably between involuntary non-visual eye movements triggered by memory processes (the focus of the current study) and voluntary eye movements, as in the eye wiggling and looking away.
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Micic D, Ehrlichman H, and Chen R (2010). Why do we move our eyes while trying to remember? The relationship between non-visual gaze patterns and memory. Brain and cognition, 74 (3), 210-24 PMID: 20864240
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
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Neuroscience
Moving the eyes but not looking - why do we do it?
To investigate, Dragana Micic and colleagues recorded the eye movements of 17 female and 12 male participants while they performed two tasks designed to be as similar as possible except for the fact that one required delving into long-term memory and the other didn't. The testing took place in a bare room with the walls draped in white sheets to reduce visual stimulation.
The first task involved the participants sitting on their own in the room, listening to three words then repeating them back after a delay (drawing on short-term or working memory). The second task was the 'remote associates test', which involves delving into long-term memory to identify the one word that matches the meaning of three others (e.g. envy, golf, beans; answer: green). All words were presented out loud, so there was no reading. The participants made far more jerky 'saccadic' eye movements during the latter task, thus suggesting that non-visual eye movements are triggered by long-term memory retrieval.
Two further studies tested whether these eye movements occur more when digging for a less accessible memory and secondly, whether they actually serve a useful function. This was achieved by varying how well the participants learned a word list (thus varying the accessibility of the memories) and, in another experiment, by instructing participants to fixate during a long-term memory retrieval task. These tests revealed that eye movements don't increase when attempting to locate a particularly inaccessible memory, and neither do they play a functional role - participants' memory performance was not impaired when they were instructed to fixate. In the jargon, this suggests that non-visual eye-movements are an epiphenomenon - triggered by long-term memory retrieval but playing no useful part in that activity.
So, why should accessing long-term memory trigger eye movements? Micic's team think the phenomenon is caused by an evolutionary hang-over. By this account, some of the same (evolutionarily older) processes involved in searching a visual scene are co-opted for use when consciously exploring the mind's archives. 'The possibility that spontaneous saccadic eye movements occur despite being non-functional may simply indicate how the addition of higher brain functions does not necessitate the "redesign of the whole brain",' they said.
At first, these new findings seem to contradict another line of research that's previously shown the beneficial role of gaze aversion (looking away from a questioner) when children and adults are working out a solution to maths and memory problems [pdf]. And to contradict the literature showing that wiggling the eyes from side to side can aid memory. Micic thinks the difference here is probably between involuntary non-visual eye movements triggered by memory processes (the focus of the current study) and voluntary eye movements, as in the eye wiggling and looking away.
_________________________________
Micic D, Ehrlichman H, and Chen R (2010). Why do we move our eyes while trying to remember? The relationship between non-visual gaze patterns and memory. Brain and cognition, 74 (3), 210-24 PMID: 20864240Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
- Early Visual Areas Of The Brain May Have A Role In Memory
The traditional view is that perceptual information is processed in early sensory regions of the brain, such as primary visual cortex, before being passed on to memory systems subserved by "high-order" brain areas, such as the prefrontal and inferotemporal...
- What Is It About Eye Wiggling That Helps People Recover From Trauma?
A controversial treatment for post-traumatic stress disorder involves the traumatised person holding a painful memory in mind while simultaneously following with their eyes the horizontal movements of their therapist's finger. Known as Eye Movement...
- Human Memory Capacity Is Mahusive!
Human memory capacity is many orders of magnitude more impressive than previously realised, psychologists have shown (the study can be accessed for free). Timothy Brady and colleagues presented 14 participants with 2,500 mundane objects, presented one...
- Electric Stimulation Boosts Beneficial Effect Of Sleep On Memory
Having a nap is a great way to consolidate your memory for what you’ve just learned. Now it appears researchers have found a way to boost this beneficial effect. A control condition confirmed the benefits of sleep: 13 participants remembered 37.42 words...
- Neuropsychology Abstract Of The Day: Memory Formation
Visualizing long-term memory formation in two neurons of the Drosophila brain Science. 2012 Feb 10;335(6069):678-85 Chen CC, Wu JK, Lin HW, Pai TP, Fu TF, Wu CL, Tully T, Chiang AS Abstract Long-term memory (LTM) depends on the synthesis of new proteins....