Level: General

Brain-booster benefits of sign language and Deafhood

In another word, Deaf gain.

And so is being Deaf -- that is, using visual-spatial medium expands our visual-perceptual skills, such as spatial awareness, mental rotation skill, visual sensitivity, etc.

These studies also imply that there are strong correlations between age of sign language acquisition and visual-perceptual skills. They also illustrate how culturally prelingual Deaf signers are the native signers.

Bilingualism boosts brain

First, a number of studies show that bilingualism is a great booster for brains. It enriches and enhances one's cognitive processes: higher abstract and creative thinking, better problem-solving, greater cognitive flexibility, better listening skills, greater academic achievement, and more! It also promotes cultural awareness, literacy, and other intellectual benefits.

No exception for any languages whether they are signed or spoken. It's not unusual to find bilingual dodas/dodas (hearing/deaf children of bilingual Deaf parents) with greater academic and cultural-social achievements (biculturalism and cultural relativism).

Sharper spatial-visual perception

"Visual-spatial perception, memory, and mental transformations are prerequisites to grammatical processing in ASL (Emmorey and Corina, 1990...).

Experiments on the relation of the use of ASL to spatial abilities, according to the illustration below, show that "deaf signing children can discriminate faces under different conditions of spatial orientation and lighting better than hearing children."

Deaf children dicriminating faces
Source: "Visual imagary and visual-spatial language" by K. Emmorey et al. P. 144.

Because, ASL speakers also use faces as one of the articulators to convey linguistic information, such as topicalization, adverbial forms, conditionals, relative clauses, sentence types, and so on. They are sensitive to subtle facial differences.

Sharper kinesthetic perception

In another experiment, deaf and hearing children were asked to write a Chinese pseudo-character each time they observed a lightpoint motion of the written Chinese pseudo-character.

The result in the illustration below shows a remarkable difference. Deaf signers can detect and interpret moving light characters better than hearing non-signers.

Deaf children recognizing characters
Source: "Visual imagary and visual-spatial language" by K. Emmorey et al. P. 145.

"In this experiment, Chinese pseudo-characters were written in the air with a light-emitting diode, which created a continuous stream of movement. Deaf signers (both Chinese and American) were significantly better than their hearing counterparts at perceiving the underlying segments of these pseudo-characters. Figure 2b [above] shows the contrast between first-grade Chinese hearing and deaf children on this task. Furthermore, Neville has shown that deaf signers have a heightened ability to detect the direction of movement in the periphery of vision (Neville, 1988)." (p 141)

The critical window of time for right angular gyrus

A study (Newmann, et al) shows that there is a critical period of time for the right angular gyrus (AG) in signed language acquisition. Both native deaf and hearing signers (who acquired the native signed language during the first years of language acquistion) show activation of the right angular gyrus when listening ASL.

The brain in native Deaf signers

These same hearing bilingual subjects don't show activation of the right AG when listening or speaking English, but only in ASL. Late signers show little or no activation in the right AG.

The right angular gyrus is associated with spatio-visual attention toward salient features and orientation in three dimensional space.

Enhanced biological motion perception

The paper "Enhanced Biological Motion Perception in Deaf Native Signers" published in an international scientific journal Neuropsychologia explains that:

"1) Deaf signers reported significantly less effort required for identifying coherent biological motion. 2) Deaf native ASL signers showed theta, mu, and beta differentiation between scrambled and biological movements. 3) These differences were seen earlier and more consistently than in hearing non-signers."

This study concludes that "native ASL users exhibit experience-dependent neuroplasticity in the domain of biological human motion perception." Ref

"The brains of native ASL users processed human actions faster and more easily than the brains of non-signing hearing persons." Ref

Peripheral vision in reading

While there were several studies that focused on reading difficulties of deaf people (who were deprived of language acquisition), fortunately there was a study who focused on deaf readers who have normal language acquisition.

Reading skills
Source: https://www.researchgate.net/publication/279279311_What_Eye_Movements_Reveal_About_Deaf_Readers

A study shows that "adult severely to profoundly deaf readers have a wider perceptual span than adult hearing readers matched on reading level. Skilled deaf readers had a wider perceptual span (up to 18 letter spaces to the right of fixation; Figure 1b) than skilled hearing readers matched on reading level did (14 letter spaces to the right of fixation)."

Hearing readers may link written words to sounds, but deaf readers focus on form-meaning connections or "orthography-to-semantic" connections.

Further readings

Emmorey, Karen; Kosslyn, Stephen; and Bellugi Ursual. "Visual imagery and visual-spatial language: Enhanced imagery abilities in deaf and hearing ASL signers." Cognition, 46 (1993), pp 139-181. http://lcn.salk.edu/publications/1993/ Emmorey%20-%20Enhanced%20Imagery%20ASL%20signers%201993.pdf

Newman, A.J., Bavelier, D., Corina, D., Jezzard, P. and Neville, H.J. (2002) "A critical period for right hemisphere recruitment in American Sign Language processing." Nature Neuroscience, 5:76-80.

"The Angular Gyrus... " http://nro.sagepub.com/content/19/1/43.full

"Enhanced biological motion perception in deaf native signers" (2021). https://www.sciencedirect.com/science/article/abs/pii/S0028393221002499

"What Eye Movements Reveal About Deaf Readers" (2015). https://www.researchgate.net/publication/279279311_What_Eye_Movements_Reveal_About_Deaf_Readers

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