Trade.Information

Details

People from different cultures use their brains differently to solve the same visual perceptual tasks, Massachusetts Institute of Technology researchers and colleagues report in the first brain imaging study of its kind.

Psychological research has established that American culture, which values the individual, emphasizes the independence of objects from their contexts, while East Asian societies emphasize the collective and the contextual interdependence of objects. Behavioral studies have shown that these cultural differences can influence memory and even perception. But are they reflected in brain activity patterns"

To find out, a team led by John Gabrieli, a professor at the McGovern Institute for Brain Research at MIT, asked 10 East Asians recently arrived in the United States and 10 Americans to make quick perceptual judgments while in a functional magnetic resonance imaging (fMRI) scanner--a technology that maps blood flow changes in the brain that correspond to mental operations.

The results are reported in the January issue of Psychological Science. Gabrieli's colleagues on the work were Trey Hedden, lead author of the paper and a research scientist at McGovern; Sarah Ketay and Arthur Aron of State University of New York at Stony Brook; and Hazel Rose Markus of Stanford University.

Subjects were shown a sequence of stimuli consisting of lines within squares and were asked to compare each stimulus with the previous one. In some trials, they judged whether the lines were the same length regardless of the surrounding squares (an absolute judgment of individual objects independent of context). In other trials, they decided whether the lines were in the same proportion to the squares, regardless of absolute size (a relative judgment of interdependent objects).

In previous behavioral studies of similar tasks, Americans were more accurate on absolute judgments, and East Asians on relative judgments. In the current study, the tasks were easy enough that there were no differences in performance between the two groups.

However, the two groups showed different patterns of brain activation when performing these tasks. Americans, when making relative judgments that are typically harder for them, activated brain regions involved in attention-demanding mental tasks. They showed much less activation of these regions when making the more culturally familiar absolute judgments. East Asians showed the opposite tendency, engaging the brain's attention system more for absolute judgments than for relative judgments.

“We were surprised at the magnitude of the difference between the two cultural groups, and also at how widespread the engagement of the brain's attention system became when making judgments outside the cultural comfort zone,” says Hedden.

The researchers went on to show that the effect was greater in those individuals who identified more closely with their culture. They used questionnaires of preferences and values in social relations, such as whether an individual is responsible for the failure of a family member, to gauge cultural identification. Within both groups, stronger identification with their respective cultures was associated with a stronger culture-specific pattern of brain-activation.

How do these differences come about" “Everyone uses the same attention machinery for more difficult cognitive tasks, but they are trained to use it in different ways, and it's the culture that does the training,” Gabrieli says. “It's fascinating that the way in which the brain responds to these simple drawings reflects, in a predictable way, how the individual thinks about independent or interdependent social relationships.”

Note for Visual Perception
In psychology, visual perception is the ability to interpret visible light information reaching the eyes. The resulting perception is also known as eyesight, sight or vision. The various components involved in vision are known as the visual system.
The visual system in humans allows individuals to assimilate information from the environment. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals. The lens of the eye focuses light on the photoreceptive cells of the retina, which detect the photons of light and respond by producing neural impulses. These signals are processed in a hierarchical fashion by different parts of the brain, from the retina to the lateral geniculate nucleus, to the primary and secondary visual cortex of the brain.

Note for Functional Magnetic Resonance Imaging
Functional magnetic resonance imaging (fMRI) is the use of MRI to measure the haemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. It is one of the most recently developed forms of neuroimaging.
BOLD effects are measured using rapid volumetric acquisition of images with contrast weighed by T2 or T2* (see MRI). Such images can be acquired with moderately good spatial and temporal resolution; images are usually taken every 1–4 seconds, and the voxels in the resulting image typically represent cubes of tissue about 2–4 millimeters on each side in humans. Recent technical advancements, such as the use of high magnetic fields and advanced "multichannel" RF reception, have advanced spatial resolution to the millimeter scale. Although responses to stimuli presented as close together as one or two seconds can be distinguished from one another, using a method known as event-related fMRI, the full time course of a BOLD response to a briefly presented stimulus lasts about 15 seconds for the robust positive response.

In figure 1, fMRI data (yellow) overlaid on an average of the brain anatomies of several humans (gray)
In figure 2, Brain activity in East Asians and Americans as they make relative and absolute judgments. The arrows point to brain regions involved in attention that are engaged by more demanding tasks. Americans show more activity during relative judgments than absolute judgments, presumably because the former task is less familiar and hence more demanding for them. East Asians show the opposite pattern.
In figure 3, John Gabrieli, the Grover Herman Professor of Health Sciences and Technology and Brain and Cognitive Sciences, left, and McGovern Institute research scientist Trey Hedden display the results from their recent psychological study.