A lifetime of paying attention to the background may have trained some senior citizens to tamp down part of their brain’s ability to see the foreground, suggest researchers in Illinois and Singapore.
“Your brain sees different things, depending on your cultural experiences and your age,” said Denise Park of the University of Illinois, who described her most recent research during the annual meeting of the Association for Psychological Science, held in Washington, D.C., the last weekend in May.
Working in collaboration with Michael Chee of the Cognitive Neuroscience Laboratory, SingHealth, in Singapore, Joshua Goh and other colleagues, Park has been studying how adults young and old process what they see. They focus on the “perceptual” parts of the brain’s visual system, those involved simply with processing the images, not with consciously analyzing them.
Their method was to put people into a functional magnetic resonance imager (fMRI), then show them a slide show of 200 images in sets of four. From slide to slide, the object in the center (foreground) of the image changes, or the object remains the same but the background changes, or both change or neither does. The volunteer test subjects, 37 young and old East Asians and 38 young and old Westerners, passively watched the show, while researchers watched the changing areas of activity in each of their brains.
After subtracting out the myriad similarities between the brain scans of older Westerners and older East Asians (average age 67), the researchers found a tiny pocket of brain matter that differed: It was active in the brains of Westerners and dormant in the brains of East Asians. And it was exactly the sort of place they expected: an object-processing area of the visual system.
“Age does change the size of the object area,” reducing the activity in the lateral occipital complex, Park said. “But in Americans the area is weak; in Asians, it is none.”
Earlier studies simply observing people’s eye movements as they scanned images has shown that East Asians tend to look more at the background, the scene, of an image and respond less to changes in the foreground, the dominant object, than Westerners do, Park said. Could a lifetime of consciously focusing on the background have changed their unconscious processing system?
Two other results from the series of scans argue in favor of that analysis, Park said. First, there was no difference in the level of activity in this object-processing area between younger Americans and East Asians (average age 22). That argues that something must happen to cause East Asians’ brains to eventually switch off that area as they grow older, likely something that takes a long time.
Second, when researchers asked the older East Asians to pay attention to the objects when looking at the images, their brain scans showed the object-processing area firing up. It is still a viable area, but apparently not used unless consciously called upon.
“These are the first studies to show that culture is sculpting the brain,” Park said. “The effect is seen not so much in structural changes, but at the level of perception.”
Park and Chee worked to ensure their fMRI readings would be comparable by using scanners in Illinois and Singapore that they have carefully calibrated with each other and by cross-training staff on both machines. Now they are performing the visual eye-movement test on the same nearly 80 volunteers whom they scanned to reconfirm the object-background differences are observably true in this set of people as well. Early results confirm the older studies.
“The neural effects are driven by what subjects look at, and that can definitively be attributed to culture,” Park said.
These studies are the first that can make that claim. Other fMRI studies, such as those by Eleanor Maguire of London taxi-cab drivers, who must memorize and master a large amount of geographical knowledge before they earn their license, have shown that attention, training and experience can change the amount of energy and brain space allotted to a certain task. Learning the streets of London is an active, conscious task, unlike gazing out the window.
Park, Chee, and their colleagues have collected data from 200 participants in their current study, 50 from each age and culture group. They aim to publish their results in 2008. They are gaining company: Culture and cognition was one of three themed daylong sessions during the Association for Psychological Science annual meeting this year, as well as the topic of dozens of other presentations.