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Think about hammering a nail right into a wall: Your dominant hand swings the hammer whereas the opposite holds the nail regular. In a brand new idea, Cornell psychology students suggest that on a regular basis duties like this are answerable for a basic side of notion within the mind: why one facet is specialised to course of high-frequency visible info, and the opposite low frequencies.
Longstanding analysis has proven that for most individuals, the mind’s left hemisphere responds quickest to quickly altering (high-frequency) enter, like hammering, whereas the suitable hemisphere processes extra static (low-frequency) occasions, like holding a nail. However scientists lacked an evidence for why that is so.
With their “action asymmetry hypothesis,” the Cornell crew explains this phenomenon and—demonstrated for the primary time in massive research—that high-frequency visible specialization is reversed in left-handed folks.
“We found the same pattern you always find in righties, whose left hemispheres are specialized for high-frequency visual perception—and the exact opposite in lefties,” mentioned Daniel Casasanto, affiliate professor within the Division of Psychology and School of Human Ecology, and director of the Expertise and Cognition Lab. “These data support our theory that the way perceptual systems are organized in the brain depends on the way we perform actions with our hands.”
Casasanto is the senior creator of “Frequency Asymmetries in Vision: the Action Asymmetry Hypothesis,” printed within the Journal of Experimental Psychology: Common. The primary creator is Owen Morgan, M.A. ’23, a doctoral pupil within the discipline of psychology.
Theories concerning the so-called hemispheric asymmetry for visible notion have advised that it could develop within the womb, or that it may very well be linked to language, for the reason that left hemisphere processes the high-frequency elements of language. The brand new examine contradicts these theories, since handedness normally doesn’t trigger any reversal in fetal growth, or within the hemisphere that processes language.
Constructing on a physique of labor Casasanto calls the physique specificity speculation—displaying that individuals’s brains and minds are organized in accordance with specifics of how their our bodies work together with the world—Casasanto and Morgan investigated the function of motor motion. They repeated experiments performed beforehand to determine hemispheric asymmetry for frequency notion, however with a key distinction. They enlisted lefties—topics routinely ignored of prior work that prioritized homogeneous samples.
“In this case,” Casasanto mentioned, “testing lefties and comparing them to the righties is the key to figuring out how perception is actually organized in the brain, and why it’s organized that way.”
A pair of experiments together with practically 2,000 contributors—roughly equal numbers of right- and left-handers, and a few blended—confirmed which hemisphere dealt with high-frequency visible processing. That was measured by response occasions when pairs of “hierarchically constructed” goal shapes had been flashed on a display screen—for instance, a diamond composed of small triangles subsequent to a triangle composed of small squares.
A 3rd experiment confirmed that each righties and lefties used their left hemisphere to course of high-frequency sounds in language. That dominated out the likelihood that so-called language laterality might clarify the hemispheric variations in visible notion.
Why may right- and left-handers course of high-frequency imaginative and prescient in numerous sides of the mind? The authors suggest two mechanisms. First, as soon as a hemisphere turns into answerable for high-frequency motion, it could be environment friendly for the mind to make connections between comparable motor, imaginative and prescient and listening to programs in the identical facet. Or maybe dominant fingers constantly feed high-frequency sights and sounds into that facet’s visible discipline.
“The fact of this action asymmetry causes asymmetries in the visual and auditory input that we give ourselves,” Casasanto mentioned. “Then the hemisphere that is used to getting either high- or low-frequency input may become specialized for that kind of information.”
The research didn’t discover a sturdy reversal in low-frequency visible enter. The researchers speculate this can be as a result of both hand might carry out many low-frequency duties, corresponding to holding a nail, specialization may be diminished.
After displaying that high-frequency visible processing reverses with handedness, offering preliminary assist for the motion asymmetry speculation, Casasanto plans in future analysis to research whether or not that can also be true for listening to. The crew additionally plans to check frequency specialization in stroke sufferers who’ve misplaced using their dominant hand, to see whether or not visible notion will get reorganized in accordance with their new habits of hand motion.
“That’s our hypothesis: that asymmetries in hand action give rise to asymmetries in perception in vision and audition,” he mentioned. “The way you perform actions with your hands influences a bunch of different cognitive functions, including language and emotion—and, we know now, visual perception.”
Extra info:
O. Morgan et al, Frequency asymmetries in imaginative and prescient: The motion asymmetry speculation, Journal of Experimental Psychology: Common (2025). DOI: 10.1037/xge0001806. psycnet.apa.org/document/2026-32729-001?doi=1
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