Unlocking the Mysteries of the Deaf Brain

 

Originally published in Research at RIT, Fall/Winter 2012

Although studied for centuries, much remains unknown about the human brain. The deaf brain in particular is still a mystery in part because this population often uses different cognitive and communication processes than hearing people. RIT's Peter Hauser is a leader in analyzing the deaf brain, how it differs from the hearing brain, and the effect of sign language on cognition.

The Deaf Brain vs. The Hearing Brain

Hauser, a deaf clinical neuropsychologist and associate professor in the American Sign Language and Interpreting Education Department at NTID, is investigating how the brain adapts and takes on different functions based on new parameters. In other words, how does deafness itself change how the brain operates?

"We really understand so little about the human brain," Hauser says. "Through my research I am seeking to uncover which cognitive processes are hard-wired, which are plastic, and how deafness or sign language may impact them."

Hauser argues the difference between deaf and hearing brains can have significant clinical impacts that can affect diagnosis and treatment of numerous diseases.

"Suppose a deaf person has a stroke, which impacts his or her communication functions," Hauser adds. "Because deaf people communicate differently and use different parts of the brain in that process, you can't assume he or she will have the same symptoms or respond to the same therapies as a person who is hearing."

Analyzing the Cognitive Process

"Peter is regarded nationally as one of the foremost experts in studies comparing deaf and hearing people's brains and function," says Daphne Bavelier, a professor of brain and cognitive sciences at the University of Rochester who has collaborated with Hauser for close to a decade. "In particular, he is leading the way in characterizing how growing up deaf or hard of hearing impacts executive functions - a set of skills that is central to academic achievements."

Much of the previous clinical research involving deaf individuals focused on restoring hearing or adjusting learning style to mirror hearing peers. Instead, Hauser focuses on deafindividuals themselves, how they learn, how they think, and how deaf brains process and use information.

Through partnerships with Gallaudet University's NSF Science of Learning Center on Visual Language and Visual Learning (VL2) and the University of Rochester's Brain andVision Laboratory, he has developed comprehensive testing procedures designed to analyze cognition in hearing and deaf individuals. His research includes studies of visual attention, the act of focusing on an object, and executive function, the part of the brain that controls behavior regulation and metacognition.

Hauser's team, which includes students and faculty through NTID's Deaf Studies Laboratory as well as faculty and students at Gallaudet and the University of Rochester, collects data on research participants from all over the world and conducts assessments in multiple written and sign languages. More than 1,000 people have participated in this testing so far.

"We conduct tests when we go to schools and camps for deaf children and academic conferences all over the world-Israel, Turkey, Germany," Hauser says.

"Seeing" Differently

Results garnered through the research, which has been funded primarily by the National Science Foundation and the National Institutes of Health, show clear differences between deaf and hearing individuals in how information is processed.

In one project, Hauser's team studied spatial visual attention in elementary school-aged children and adults to compare differences between populations. They found that elementary aged deaf children perform similarly to their hearing peers. However, as people age, differences in attention grow wider, as deaf adolescents and young adults were more attentive to peripheral events. Hauser explains, "this seems to be an important adaptive ability that makes deaf individuals more aware of what is happening around them, to increase their incidental learning, and to prevent them from dangers."

Hauser says it has been generally understood that deaf people learn to pick up visual cues of what is happening peripherally quicker than hearing individuals, because they have fewer senses to rely on.

"Attention is a key psychological indicator of how information is transmitted from the senses to the brain," he adds. "By showing how this works differently in deaf people, we can assist in developing techniques that foster visual learning."

Hauser has further examined differences in visual processing by comparing reading comprehension between hearing and deaf people. His team tested children ages 8 to 16 from four different countries (with five languages) on letter recognition, word recognition, and how the reader processed semantics and sentence processing. Participants included deaf children of deaf parents, deaf children with hearing parents, hearing children, and hearing children with dyslexia.

The preliminary findings appear to suggest that early sign language acquisition and deaf parents' indigenous knowledge on how to raise deaf children prepare students to become successful readers regardless of the language, written orthography type, or region. Deaf children raised by deaf parents are able to achieve the same basic reading skills as hearing individuals early in life, suggesting that deafness per se does not cause reading challenges but what does have an effect is being raised in improvised visual language environments that do not foster visual learning.

Hauser's neuroimaging research also suggests that skilled deaf readers use different parts of their brains for processing reading.

"Traditional methods for teaching reading and assessing comprehension are based on how hearing people learn and do not generally take into account the visual needs of deaf learners," Hauser says. "Our research shows that deaf students do not necessarily learn to read more slowly than hearing students-just differently."

Understanding Executive Function

"Attention control, emotional control, impulse control, memory, organizing your thoughts, planning your thoughts-these are all components of executive function that continue to develop in the brain until early adulthood," Hauser says. "And language appears to be a necessary component of executive function development. But for the majority of deaf people growing up in hearing families, language development is delayed."

Hauser argues that inefficient executive function development can have a negative impact on learning and academic achievement. His team is conducting a series of experiments, using both deaf and hearing participants, to investigate the impact of language learning on executive development.

"The problem we encountered when beginning this research was that there are no standardized tests available to measure individuals' sign language fluency," he continues. Given this, the team developed a highly sensitive test of competency in American Sign Language that can easily be administered in a short period of time. Hauser developed a Web-based administration protocol so the test can be administered remotely, with participant responses sent to his laboratory for analysis.

The test is currently being used in a number of psychological, linguistic, and cognitive neuroscience research studies at universities all over the country.

"The creation of this test has finally enabled researchers to test research questions related to the effect of sign language skills on learning and cognition," Hauser adds.

The test has already been adapted to measure German and British sign languages and Hauser hopes to further expand its use in the future.

Promoting the Deaf Learner

On top of his basic research efforts, Hauser has sought to enhance understanding of deaf learners and promote educational and outreach opportunities in the deaf community.

This includes efforts to disseminate information on deaf cognition to the broader scientific and education community as well as supporting the next generation of researchers.

Hauser has presented his research at numerous international conferences, served as a presenter/mentor for the Youth Leadership Conference of the National Association of the Deaf, and served as a delegate to the Test Equity Summit, which sought to ensure that educational testing better accounted for deaf learners. He also co-edited, with NTID Professor Marc Marschark, the 2008 book Deaf Cognition: Foundations and Outcomes, and the 2011 book How Deaf Children Learn: What Parents and Teachers Need to Know, both published by Oxford University Press.

Hauser has also worked with numerous students at RIT, NTID, and his partner institutions to promote their research efforts and enhance enthusiasm for the topic as a whole.
Erin Spurgeon, who enjoyed Hauser's enthusiasm for his subject matter when he taught a psychology class she was enrolled in while an RIT/NTID master's student, ended up working as his research associate in the Deaf Studies Laboratory. She worked on several cognition projects and traveled with Hauser to the University of Haifa in Israel in 2009 and to Turkey in 2010 for his international research team meetings. Spurgeon is currently pursuing her Ph.D. in language and communicative disorders in a joint program at the University of California at San Diego and San Diego State University.

"The opportunity to work with Professor Hauser as a research associate was one of the most valuable experiences I had in preparation for this doctoral program," she says. "Students who are interested in deaf research are fortunate to work with a knowledgeable and respected member of the scientific community."

With continued research based at RIT/NTID, Hauser believes a legacy is being built here for deaf cognition, education, and outreach in deaf studies and sign language research.
"My hope is to bring more people into research, have junior faculty involved more, mentor them, create a deaf-friendly lab environment where people can come in and learn how to conduct research," Hauser adds.

 

Unlocking the Mysteries of the Deaf Brain
Thu, 10 Nov 2011 17:59:00 GMT