Deaf Individuals Read More Efficiently
Have you ever wondered if when one sensory module is impaired, other sensory systems learn to develop other means to counteract that deficiency? Past studies have shown that deaf individuals have a larger capability to focus on simple visual stimuli in the parafovea. The parafovea is a region in the eye that surrounds your fovea, the central pit of the eye that is responsible for sharp, central vision. Large rates of 
illiteracy in the deaf population have caused people to question whether deaf individuals wide range of focus in the parafovea, causes reduced processing in the fovea. A recent study done at the University of California San Diego has shown that deaf people’s parafoveal vision does not cause reduced vision on the fovea and they actually have a wider range of sharp vision which researchers found and can actually aid them in complex visual tasks such as reading (Bélanger et al. 2012).
This study is titled, Skilled Deaf Readers Have an Enhanced Perceptual Span in Reading. A perceptual span refers to the area in which the human eye can seeclearly enough to read text. The researchers in this experiment were testing to see what the width of deaf readers was in comparison to hearing readers. The procedure the researchers used was relatively simple. First they selected sixty participants, forty from San Diego’s deaf community ranging from ages 20 to 45 years old and twenty skilled readers from ages 21 to 43 who were able to hear and spoke English as their native language. All of the participants in the study had normal vision and first completed a test that assessed their reading level. The deaf readers were then split into two groups, one of skilled deaf readers and one of less-skilled deaf readers. After splitting the participants into groups, the researchers created 165 simple sentences that were each 10 to 17 words and would be presented on a single line to the participants. The eye movement of each participant was tested using a monitoring device and head movements were minimized using a chin and headrest
The participants were given instructions to read each sentence and press a button when they were finished. They then participated in a short series of steps to calibrate the eye-tracking device. Next, each participant was given 15 practice sentences so they were able to understand how the moving window worked. After the practice they were given all test sentences one at a time. The researchers calculated the reading rate of the readers using words per minute (wpm) and found that when the window size increased, the reading rate for both skilled deaf readers and less-skilled deaf readers also increased while skilled hearing readers had no increase in reading rate with larger window sizes.The researchers used four different window sizes in their design method along with a baseline no-window condition where the entire sentence was visible. The four different window sizes all showed 4 visible characters to the left of focus point and either 6, 10, 14, or 18 character spaces on the right of the focus point. In the moving window conditions, the characters outside the window were replaced with an “x”, and as the window continued to move along the sentence, new characters were revealed and previous characters were again replaced with the “x”.
These results show that skilled deaf readers were the most negatively affected by the loss of information further down the line of text which means they are much more efficient readers with a large window and when they are given a smaller window (less words available at once), they don’t read as efficiently. These skilled deaf readers have a wider range of sharp vision because they have good vision in their fovea, as well as sharpened vision in their parafovea. With this wider range of vision, these skilled deaf readers can take in more words per minute while reading than skilled hearing readers, disproving the previous suggestion that their sharp parafoveal vision causes deficits in other parts of their eye. This study also showed that both skilled deaf readers and less skilled deaf readers had a wider range of vision than skilled hearing readers, and the difference in their reading level is caused by other factors. This study is extremely important in the discussion surrounding illiteracy in the deaf population. As we discussed in class, our sensory memory system only has a certain storage capacity. These deaf individuals that show a larger visual sensory modality than hearing individuals may be able to give us information surrounding the limitations of our sensory systems and how capacity in sensory memory systems could possibly shift. For example if an individual is deaf, could it free up additional space in the sensory memory for functioning senses?
Check out my peers article on parafoveal recognition while reading here
References:
Belanger, N. N., Slattery, T. J., Mayberry, R. I., & Rayner, K. (2012). Skilled Deaf Readers Have an Enhanced Perceptual Span. Psychological Science, 23(7), 816-823.
Bélanger N. N., Baum S. R., Mayberry R. I. (2012). Reading difficulties in adult deaf readers of French: Phonological codes, not guilty! Scientific Studies of Reading, 16, 263–285.
Image 1: https://en.wikipedia.org/wiki/Macula_of_retina
Image 3: http://pss.sagepub.com/content/23/7/816.full
The opening question of this blog post immediately caught my attention—Yes, I have wondered how the other senses would respond if one were taken away. It comes as no surprise to me that deaf individuals have enhanced visual attention skills that facilitates complex cognitive tasks such as reading. As the study described found, the expected perceptual span corresponding to an individual’s reading ability was significantly larger for deaf readers compared to that of hearing readers. This idea that impaired sensory modules may effect and even enhance other senses immediately made me think of Synesthesia, which I learned about in my neuroscience and psychology seminar.
Synesthesia is a neurological condition in which the stimulation of one sensory system causes automatic, involuntary experiences in a different sensory system. To better understand this complicated phenomenon, one example of the most common types of synesthesia is sound to sight synesthesia, or “colored hearing”, which is when individuals can “see with their ears”; this means that sounds, which stimulate receptors in our auditory system, actually elicit colored, visual experiences. We can analyze this phenomenon in regard to what we have learned about pattern recognition in cognitive psychology class. External information from our environment is received by our sensory system. Our sensory memory recognizes sensations according to the incoming modality specific input (wavelengths, sound waves, etc.). The distal stimuli represent information from the environment, which our receptor cells directly receive. The sensory system processes that information, decoding it and turning it into neural signals that can be interpreted by the brain, called the proximal stimulus. The generated neural signals are transported by a nerve conduit, delivering the information to the appropriate brain region where it can be processed and perceived as a sensory experience. From what we have learned in class, I would guess that for synesthetes, there seems to be some variation in this process; the sensory system must decode the distal stimuli such that it is decoded and converted into neural signals that are processed by multiple brain areas associated with different senses. So for colored hearers, sounds not only elicit auditory perceptual experiences, but they also illicit visual perceptual experiences. This phenomenon demonstrates the possibility of sensory crossover and modulation in the inner workings of sensory system. I bring up synesthesia in regard to the current post because I wonder if the surrounding research could explain the results of this post’s described study.
Since variation in the stages of processing is possible, as exhibited by synesthetes, could it be possible that similar variations occur in deaf individuals? If humans are capable of modulating our sensory system so that other senses can perceive various module inputs, then could it be possible that the deaf individuals have developed an alternate sensory system? Perhaps deaf individuals exhibited enhanced reading skills because they have specialized their sensory system in such a way that favors visual information, expanding the ways in which our brain perceives that information.
For readers further interested in the topic of cognitive processes of the deaf population, I found some additional information that I thought was really interesting regarding sensory crossover and deaf individuals.
Neuroscientist, David Eagleman, gives a really interesting Ted talk regarding the phenomenon of sensory crossover, which can be viewed HERE. In his speech he explains his research that is interested in sensory substitution for deaf individuals. He aims to develop an alternate process in which sounds from the external world can be converted in a way that a deaf person can understand. To do this, he developed a tablet and a specialized vest that is covered in vibratory motors; he programed and coded the tablet and vest so that sounds in the environment are mapped onto the vest, translating the sounds into a corresponding pattern of vibrations. The idea is that through training of the dynamic patterns of vibration, individuals can actually start understanding the language of the vest through feeling vibrations rather than hearing. So researchers are actually developing alternate means of hearing for individuals lacking that sensory functioning altogether!
The idea of one sensory module interpreting the information of a different sensory module made me think of bats, which are notorious for their ability to function in the dark. Bats use echolocation to “see” in the dark. They have developed a very impressive sensory system that allows them to use their advanced hearing to compensate for a lack of vision during the nighttime; despite it being dark and difficult to see, they are able to hunt prey because of their specialized auditory system. Furthermore, this makes me wonder if deaf individuals could have developed an enhanced visual system in a similar manner. Could it be possible that when one sensory module is impaired, other sensory systems learn to develop other means to counteract that deficiency? In cognitive psychology class we have discussed the limitations of each of our sensory systems. Capacity is a factor that limits both the sensory memory and the short-term memory. I wonder if lacking one sense, such as hearing, frees up additional space in the sensory memory for functioning senses.
Ted Talk referred to above: https://www.ted.com/talks/david_eagleman_can_we_create_new_senses_for_humans/transcript?language=en
As Katherine mentioned in her comment, it’s interesting to see how our body compensates for losing a particular sense by virtually enhancing the other senses. Upon thinking about this, the first things that come to mind is the superhero “Daredevil” that loses his vision, and in return gains a variety of superhuman abilities via his other senses. Obviously, this is a huge exaggeration, but it’s really interesting to read about how there are real life cases of other senses actually increasing and being better than the average person.
After reading this post, it got me thinking about real world applications of this study’s findings, and I’m curious as to whether deaf people not only are more efficient at reading but also if they are better are reading comprehension than people with healthy vision. A theory for this would be that since deaf people don’t have any auditory sensory information that they would be able to attend to and focus on reading better as no auditory distractions would exist. Furthermore, no attentional resources would have to be spent on auditory information.