I have included this article though it is dated 2002 because I feel it is totally relevant to today and whaqt is going on today with research ongoing with both sign language and brain research. Karen Emmorey appears to be very involved in this and other research to do with sign language. I have included a link to her book and more information on her at the end of the article. Enjoy
Emmorey, K. (2002). Sign language and the brain. Language, Cognition, and the Brain:
Insights from Sign Language Research, 9, 271-314
This section doesn't focus exclusively on the brain itself, but incorporates a number of developmental components that have been observed as being influenced by the addition of sign language.
According to Piaget (1955), sign is a more natural modality for a children's exchange of ideas, than is spoken language: "gesture and mime...language in movement...is the real social language of the child" (p.77). Despite the fact that most children don't naturally begin to show simple gestures such as waving "hi" or "bye" until about eight months old, it has been found that infants who are regularly and consistently exposed to sign language at approximately six months old, are able to begin expressive communication at around eight months. It is easier for children to communicate with their hands than to solidly utilize the mechanics necessary for verbal communication, (Garcia, 1999) because the mouth and other language articulators are slower to mature than the motor areas of the body (Snoddon, 2000) and this differential is maintained during early development and continues in childhood. Additionally, the visual cortex matures prior to the auditory cortex, which is another reason why signing has great impact (Daniels, 1996). Expressive language (language used to express oneself, as compared to receptive language, or comprehension of language used by others) relies on the ability to understand both context and basic sentence construction. Because a parent using sign language in conjunction with speaking to their baby tends to speak more slowly and at a relatively controlled rate, there is a greater likelihood that the child will understand the message that is being conveyed and that communication will be more successful. (Check out this wonderful video of infants signing from "CBC News Indepth": http://www.cbc.ca/news/background/babysign/) Furthermore, the capacity to play is generally accepted as a cause and correlate of cognition, social growth and language ability, and using sign language with hearing children has been shown to enhance children's facility for play by increasing their understanding and use of symbols (Daniels, 1996).
This positive affect on expressive language development is seen in older "nursery school age" children as well, and has been documented in kindergarten children's use of descriptive adjectives and adverbs (Daniels, 1996). Additionally, a study conducted by Marilyn Daniels in 1994 showed a statistically significant improvement in receptive English vocabulary for pre-kindergarten students in Maryland who received nine months of sign language instruction combined with spoken English. The teacher communicated with the students about half of the time in a combination of sign and spoken English, a quarter of the time in English alone, and a quarter in sign alone. The children's scores on the Peabody Picture Vocabulary Test rose 17.24 points during the school year, as compared with an increase of only 6.48 in the control group of students, who received traditional education without the addition of sign. A follow-up study on these same children during their kindergarten year found that the students' vocabulary growth was sustained in the absence of any further use of sign language or sign instruction (Daniels, 1996). The teachers who had utilized signs reported that the children's ability to focus had been easily established from the start of the year. This has been attributed to the fact that signing requires individuals to see all that is happening, which leads to maintained eye contact, and careful attention to the hands, eyes and facial expressions.
When an infant begins to sign, the parent will naturally respond to the topics solicited by the child, thus bathing the child with words and sentences that are directly relevant to the topic they've chosen. This provides them with greater exposure to words (and topics) they care about. Additionally, according to Acredolo and Goodwyn, signing with babies creates a mental framework, which makes it easy to incorporate words as soon as the baby's vocal chords are developed enough to be used. In their research on babies' utilization of a program they developed called Baby Sign they found that changes occur in the brain every time a baby uses a sign, and this brings the child closer to mastering language. Talking depends on the circuitry in the brain, which develops along with a child's experience with language, and signing begins the process of language processing earlier, giving the circuitry a "jump start" (Acredolo & Goodwin, Baby Signs: How to Talk With Your Baby Before Your Baby Can Talk). Furthermore,
Sign language can further help in the communication process because it utilizes both visual and kinaesthetic cues, which, when combined with the auditory cues of spoken language, provide opportunities for infants to receive information at multiple levels and through various modalities (Haskins, 2002). These additional sensory channels in the brain provide a richer language base (Daniels, 1996). This combinatory approach appeals to a variety of learning styles: language is represented through sight, hearing, and movement, which can accommodate a variety of learning styles. The visual and iconic nature of sign languages offers additional stimulation to developing brains, and provides new and creative ways to engage a child’s mind. The signs often provide strong visual clues to their contextual meanings, which aids in quick conceptual acquisition. In the early 19th century, Thomas Galludet, who was a pioneer of education for the deaf in the U.S., encouraged the hearing siblings of deaf individuals to learn to sign because, among other things, it would increase their spoken vocabulary and language proficiency. Consistent with this idea, it was written in an 1853 issue of the American Annals of the Deaf and Dumb, "The more varied the form under which language is presented to the mind through the various senses, the more perfect will be the knowledge of it acquired, and the more permanently will it be retained" (Daniels, 1996). Anecdotal evidence of families who implemented this practice reported that both vocabulary and language capacity of their hearing child were increased.
Research reported on by Marilyn Edmunds and Debra Krupinski has shown that information about a child’s ability to comprehend the meaning of a word, whether spoken or written, can be revealed by their level of competency with oral language. Challenges with reading ability have been linked to weak oral language skills. Signing combined with spoken language provides two repetitions of a word, in two modalities. These multiple opportunities can help to enhance a child’s oral language skills, thus setting the stage for better reading comprehension. The inability to isolate speech sounds due to deficiencies in phonemic segmentation skills is a primary problem for people with reading and spelling difficulties (Felzer, 2000). Successful readers have strong skills in phonemic awareness, which is the ability to hear, identify and utilize through manipulation the different sounds in spoken words. Fingerspelling has been observed to support the development of phonemic awareness. Furthermore, it is helpful to young children in that it can make clear some common mistakes. For example, when singing the alphabet song, many children don’t realize that “duh-bul-you” is only one letter. It can also help to clarify some other letter errors, such as distinguishing c from z, or b from d (Edmunds & Krupinski). And because children can fingerspell before they acquire the manual dexterity to write words with paper and pencil, they are provided with an early and convenient alternative form of writing (Daniels, 1996).
When it comes to ASL in particular (as compared to other sign systems), the benefits are even more far-reaching. Studies have found that languages are categorically coded in separate memory stores, and because ASL is a real language, it is presumably stored in a separate memory channel in a baby’s brain (Daniels, 1994). Sign language can help the brains of hearing children to develop further than those of their counterparts who don’t receive any second language exposure. This greater development provides an additional location in the brain for search and recall (Daniels, 1996). Additionally, when more pathways are created, memory is stronger (Edmunds and Krupinski, 2005, pbs.org).
According to Marilyn Daniels, PhD, because “ASL requires babies to use their eyes more than any other spoken language,” brain development in hearing babies is even further enhanced. Daniels says “all languages are actually stored in the left brain,” but the right hemisphere is where visual information is processed, and signing is received by the right hemisphere of the brain, and processed by the left. So, babies that learn to use sign language use both the right and the left brain, which builds more synapses (Daniels, 1996). (For more information on language as a predominantly left-hemisphere function, see Language Development, 3rd Ed., Erika Hoff, 2005, pp. 45-65.)
A More Scientific View:
One finding that emerges from studies of both neurologically intact and brain-injured signers, is that the left-cerebral hemisphere is critical for sign language processes, as it is for spoken language. The data from sign language eliminates two competing hypotheses regarding the nature of this specialization.
First, sign language doesn’t rely on the generation or perception of fast acoustic transitions, and yet the left hemisphere is dominant for processing sign language to the same degree that it is for spoken language. Second, complex gesture can be dissociated from sign language production, suggesting distinct underlying neural systems. Both neural plasticity and rigidity are observed for the neural organization within the left hemisphere for Deaf signers. Neural plasticity is observed for the auditory related cortex, which has received little or no auditory input, but nonetheless is engaged in processing the visual input of sign language. More surprising, maybe, is that the same neural structures (i.e. Broca’s area, Wernicke’s area) are engaged for the production and comprehension of both signed and spoken language. This neural invariance across language modalities points to a biological or developmental bias for these neural structures to mediate language at a more abstract level, divorced from the sensory and motor systems that perceive and transmit language. For both spoken and sign language comprehension, the right hemisphere appears to be involved in processing some discourse-level functions, facial affect, and even some aspects of complex sentence comprehension. However, for sign language, the right hemisphere may play a unique role in the production and comprehension of the topographic functions of signing space, particularly as conveyed by classifier constructions.
(Please remember when reading this we are looking at the use of Auslan (Australian sign language) not ASL which is American Sign Language.)
Language, Cognition, and the Brain: Insights from Sign Language Research
by Karen Emmorey. 383 pgs.
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publication details
Place of Publication: Mahwah, NJ
Publication Year: 2002
