Learning another language has wonderful benefits. Studies show that bilingualism has great cognitive benefits. Raising a child with two or more languages is a blessing. But, that doesn't stop adults from learning another language and still enjoying some cognitive benefits.
Not just bilingualism, but why not bimodal also? Why should every child become a bilingual-bimodal from birth or childhood in an ASL-speaking environment? And, why would adults want to learn sign language?
Bimodalism -- that is, using visual-spatial medium expands your visual-perceptual skills, such as spatial awareness, mental rotation skill, visual sensitivity, and more!
We can look at codas/dodas (hearing/deaf children of Deaf parents) who have greater academic (bilingualism and cognitive benefits) and social (biculturalism and cultural relativism) achievements.
Bilingualism of any languages (whether signed or spoken) is a great booster for brains, according to a number of studies. 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.
Remember speech is not a language but a medium or modality, whereas language is amodal, according to neuroscience and lingusitics studies.
"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."
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.
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.
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)
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 show activation of the right angular gyrus when listening ASL.
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.
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
Related posts: top benefits for learning sign language.