Research study asks: Do deaf and hearing brains do math differently

When you look at a math problem, your brain gets to work. It needs to process the numbers and figure out if you're adding, subtracting, multiplying, or dividing. Then it makes the necessary calculation. There have been decades of research on how this happens and which areas of the brain are most involved - but only in hearing, speaking people.

"We don't know if studying or learning arithmetic in sign relies on different areas. For people who attended deaf schools, and had all of their education in ASL, what does that look like? How does the brain work?," says Dr. Ilaria Berteletti, Assistant Professor and Program Director of the Ph.D. in Educational Neuroscience Program. She notes that we also don't know what math looks like in the brains of deaf people who are delayed signers.

These are two of the major topics Berteletti plans to explore with her project, "Deaf signers and mathematical cognition: How language modality and time of language acquisition affect the neural correlates of arithmetic processing." A three-year, $1.4 million award from the National Science Foundation (Award ID: 2349782) will allow her lab to conduct research on at least 120 adult subjects, divided between early signers, late signers, and hearing non-signers.

"We will test the assumption that the models we've established are applicable to everyone," she says. The results will either confirm that the brain operates the same way regardless of language modality, or they will show that the brain is shaped by our experiences and adapts to various circumstances.

For educators, this has the potential to be very powerful knowledge. "We could better understand how to make a math curriculum tailored to sign language, and not just borrow pedagogical tools from research on hearing individuals and assume they will work with deaf signing children," Berteletti says. "That way we can find what the appropriate tasks, training, and assessments should be." For instance, when signers have math disabilities, maybe we should emphasize visual skills, she suggests.

Berteletti also hopes the work can shed light on the brain's resilience, particularly in late signers. "Some report being language deprived, but being able to do numbers,'" she notes.

The study will rely on data collected through functional magnetic resonance imaging (fMRI), a technology that indicates which areas of the brain are fired up at any particular moment. Subjects inside of a scanner will be asked to complete several simple tasks related to subtraction and multiplication. On a screen, they will see a question and an answer, and they will press buttons to indicate whether this is right or wrong, Berteletti explains.

There will also be other tasks to help Berteletti and her team understand what each area active during arithmetic is really doing. For example, one task will use images to help localize the language areas. Maybe those areas are activated during multiplication, but not subtraction, Berteletti says.

The protocol's most exploratory element is a finger movement task, which will help the researchers pinpoint what it looks like in the brain when subjects move their fingers. Berteletti's team will use this information to see if sign language users rely on these same areas when doing math. "What does arithmetic retrieval look like in sign language? There might be activation in the hands areas even if you're not moving your fingers because that's how problems were learned," she says.

Several pilot participants tested out this protocol earlier with Dr. SarahBeth Sullivan, PhD-'22, and Dr. Sarah Kimbley, PhD-'23, who used the data in their dissertations. (The top image comes from Sullivan's work.) PEN graduate student Casey Spelman will be recruiting more subjects soon. Anyone interested can contact [email protected].