A new study suggests that intelligence is more about what the brain chooses to ignore than simply its ability to process information rapidly.
The research, which was published in the journal Current Biology, suggests new ways of testing intelligence that may be less biased by cultural knowledge— as many have claimed other IQ tests are. It may also help to explain the profound intellectual talents of some autistic people. “It’s a really interesting potential new paradigm,” says Scott Barry Kaufman, adjunct assistant professor of psychology at New York University, who was not associated with the research.
Scientists led by Duje Tadin, assistant professor of brain and cognitive sciences at the University of Rochester, studied 67 people in two similar experiments. Before beginning, all participants took IQ tests: the first twelve took short versions, the rest sat for the full battery of testing. Then they watched videos of both small and large objects that moved, very slightly, either to the right or to the left of a screen and tried to identify the direction of motion. The scientists knew that tracking larger objects is actually more challenging, possibly because in the natural world, large background movements like those of trees rustling in the wind are typically irrelevant to human activity— so the brain automatically dismisses or ignores them. “What you want to see is if there’s an animal hiding in the tree about to jump you,” says Tadin.
The researchers found that the difference between an individual’s ability to correctly identify the direction of motion between the small and large objects was strongly linked to their IQ. “The more they struggled with the big ones and the better they were at the small ones, the better their IQ was,” Tadin explains. In other words, intelligence may require a trade-off between being good at identifying motion in small objects at the cost of not being able to do so with large ones. Tadin and his colleagues called the measure of this skill the “suppression index.”
“This is the first study I’ve ever seen that shows that the exact same ability to inhibit irrelevant and distracting information [on low levels] is correlated with higher order functions,” says Kaufman.
Although people have been trying to connect intelligence with perceptual speed and accuracy since smartness was first studied, prior research found only small correlations with measures of sensory information processing speed. “For intelligence, you need to be able process relevant information fast, but you also need to focus on the most relevant information and filter out what’s irrelevant,” says Tadin.
That type of skill can be both disturbed in some ways and enhanced in others in autism. In previous research, Tadin examined sensory processing in autistic people, and found that autistic children were twice as effective in detecting motion of high contrast objects as typically developing kids. This heightened sensitivity may explain why autistic people frequently find themselves overwhelmed by strong sensory experiences like bright lights and loud noises that most of us register, but ignore.
Such a sensitivity, however, may be linked to autistic individuals’ intellectual talents— and testing for this kind of sensory skill might reveal intelligence that is not captured by traditional IQ testing. “People with high functioning autism are really good at focusing on the local aspects of perception and totally ignoring the bigger picture,” says Kaufman. “This new paradigm might [offer a way] to measure the intelligence of autistic people, which is often underestimated because the tests are verbally loaded.”
But while it might seem that the suppression index would be more strongly correlated with visual and spatial aspects of IQ, the measure actually showed a tighter connection with verbal intelligence. “That took us by surprise,” says Tadin. He says that verbal IQ has the strongest association to the overall score, but it is not clear why the connection appeared with this skill.
Neither Tadin nor Kaufman sees the new test as a replacement for IQ testing, but if further research confirms the strength of the correlation between the suppression index and IQ, and determines how it changes with age, it could help provide additional information on intelligence. For example, it might be useful for children from disadvantaged backgrounds whose intelligence on current IQ tests may appear artificially low because they haven’t received the right type of intellectual stimulation or been exposed to the same cultural environments reflected in the test questions.
The research also shows how intellectual ability may rely on the ability to avoid distraction. And that raises interesting questions about the impact that the constant diversions of the digital world could have on the intellect of future generations. “It’s getting worse and worse,” Tadin says of the technology that surrounds us and divides our attention. To maintain our intelligence, he adds, “We need to filter out some of this stuff.”