A child's brain has to work overtime in a noisy classroom to do its typical but very important job of distinguishing sounds whose subtle differences are key to success with language and reading.
But that simply is too much to ask of the nervous system of a subset of poor readers whose hearing is fine, but whose brains have trouble differentiating the "ba," "da" and "ga" sounds in a noisy environment, according to a new Northwestern University study.
"The 'b,' 'd' and 'g' consonants have rapidly changing acoustic information that the nervous system has to resolve to eventually match up sounds with letters on the page," said Nina Kraus, Hugh Knowles Professor of Communication Sciences and Neurobiology and director of Northwestern's Auditory Neuroscience Laboratory, where the work was performed.
In other words, the brain's unconscious faulty interpretation of sounds makes a big difference in how words ultimately will be read. "What your ear hears and what your brain interprets are not the same thing," Kraus stressed.
The Northwestern study is the first to demonstrate an unambiguous relationship between reading ability and neural encoding of speech sounds that previous work has shown present phonological challenges for poor readers.
The research offers an unparalleled look at how noise affects the nervous system's transcription of three little sounds that mean so much to literacy.
The online version of the study will be published by the Proceedings of the National Academy of Sciences (PNAS):
http://www.pnas.org/papbyrecent.shtml
The new Northwestern study as well as much of the research that comes out of the Kraus lab focuses on what is happening in the brainstem, an evolutionarily ancient part of the brain that scientists in the not too distant past believed simply relayed sensory information from the ear to the cortex.
As such, much of the earlier research relating brain transcription errors to poor reading has focused on the cortex -- associated with high-level functions and cognitive processing.
Focusing earlier in the sensory system, the study demonstrates that the technology developed during the last decade in the Kraus lab now offers a neural metric that is sensitive enough to pick up how the nervous system represents differences in acoustic sounds in individual subjects, rather than, as in cortical-response studies, in groups of people. Importantly, this metric reflects the negative influence of background noise on sound encoding in the brain.
"There are numerous reasons for reading problems or for difficulty hearing speech in noisy situations, and we now have a metric that is practically applicable for measuring sound transcription deficits in individual children," said Kraus, the senior author of the study. "Auditory training and reducing background noise in classrooms, our research suggests, may provide significant benefit to poor readers."
For the study, electrodes were attached to the scalps of children with good and poor speech-in-noise perception skills. Sounds were delivered through earphones to measure the nervous system's ability to distinguish between "ba," "da" and "ga." In another part of the study, sentences were presented in increasingly noisy environments, and children were asked to repeat what they heard.
"In essence, the kids were called upon to do what they would do in a classroom, which is to try to understand what the kid next to them is saying while there is a cacophony of sounds, a rustling of papers, a scraping of chairs," Kraus said.
In a typical neural system there is a clear distinction in how "ba," "da" and "ga" are represented. The information is more accurately transcribed in good readers and children who are good at extracting speech presented in background noise.
"So if a poor reader is having difficulty making sound-to-meaning associations with the 'ba,' 'da' and 'ga' speech sounds, it will show up in the objective measure we used in our study," Kraus said.
Reflecting the interaction of cognitive and sensory processes, the brainstem response is not voluntary.
"The brainstem response is just what the brain does based on our auditory experience throughout our lives, but especially during development," Kraus said. "The way the brain responds to sound will reflect what language you speak, whether you've had musical experience and how you have used sounds."
The Auditory Neuroscience Lab has been a frontrunner in research that has helped establish the relationship between sound encoding in the brainstem, and how this process is affected by an individual's experience throughout the lifespan. In related research with significant implications, recent studies from the Kraus lab show that the process of hearing speech in noise is enhanced in musicians.
"The very transcription processes that are deficient in poor readers are enhanced in people with musical experience," Kraus said. "It makes sense for training programs for poor readers to involve music as well as speech sounds."
Achievement Gaps: How Black and White Students in Public Schools Perform in Mathematics and Reading on the National Assessment of Educational Progress
In 2007, mathematics scores for both Black and White public school students in grades 4 and 8 nationwide, as measured by the main NAEP assessments of the National Assessment of Educational Progress (NAEP), were higher than in any previous assessment, going back to 1990. This was also true for Black and White fourth-graders on the NAEP 2007 Reading Assessment. For grade 8, reading scores for both Black and White students were higher in 2007 than in the first reading assessment year, 1992, as well as the most recent previous assessment year, 2005.
White students, however, had higher scores than Black students, on average, on all assessments. While the nationwide gaps in 2007 were narrower than in previous assessments at both grades 4 and 8 in mathematics and at grade 4 in reading, White students had average scores at least 26 points higher than Black students in each subject, on a 0-500 scale. This report will use results from both the main NAEP and the long-term trend NAEP assessments to examine the Black-White achievement gaps, and changes in those gaps, at the national and state level.
The main NAEP 2007 Reading and Mathematics Assessments included grade 4 and grade 8 students both nationally and for all 50 states, as well as the Department of Defense Education Activity (DoDEA) and the District of Columbia (hereinafter referred to as states). Not all states had Black (or White) student populations large enough to provide reliable data, and not all states participated in the earliest NAEP state assessments.
Most of the data in this report comes from the main NAEP assessments, supplemented with some data from the NAEP long-term trend assessments. Main NAEP assessments, which began in 1990 for mathematics and 1992 for reading, are administered at the fourth and eighth grades, both nationally and at the state level. Because main NAEP only assesses public schools in its state assessments, this report contains only public school results. The most recent results in this report are for 2007.
NAEP long-term trend assessments are administered by age rather than grade. This report references long-term trend assessment public school results from the earliest assessment through 2004, with results for ages 9 and 13 instead of grades 4 and 8. The long-term trend assessments provide public school results for mathematics going back to 1978 and for reading going back to 1980, at ages 9, 13, and 17, at the national level only, on a 0-500 point scale.
At both ages 9 and 13, mathematics scores for both Black and White students were higher in 2004 than in any previous assessment. The 23-point Black-White achievement gap in mathematics for age 9 public school students in 2004 was narrower than in the first assessment in 1978 but not significantly different from the gap in the most recent previous assessment in 1999. The same was true for the 26- point gap at age 13.
For age 9 reading, scores for both Black and White students were higher in 2004 than in any previous assessment, going back to 1980. The 26-point gap between Black and White students in 2004 was not significantly different from the gap in 1980, but was narrower than the gap in 1999. At age 13 reading, scores were higher for Black students in 2004 than in 1980, but did not show a significant difference from 1999. Scores for White students were not significantly different for either comparison year. The 21-point gap in student performance at age 13 reading in 2004 was narrower than in both 1980 and 1999.
The following two sections summarize state-level achievement gaps between Black and White students in the main NAEP assessments in mathematics and reading.
State Black-White Achievement Gaps—Mathematics
* At the state level, gaps in grade 4 mathematics existed in 2007 in the 46 states for which results were available. In 15 states, the 2007 gaps were narrower than in 1992, as Black students demonstrated a greater gain in average scores than that of the White students.
* At grade 8, mathematics gaps existed in 2007 in the 41 states for which results were available. The gaps were narrower in 2007 than in 1990 in four states: Arkansas, Colorado, Oklahoma, and Texas. In all four, scores for both Black and White students increased, but scores for Black students increased more.
* At grade 4, five states had mathematics gaps in 2007 that were larger than the national gap of 26 points, while 10 states had gaps that were smaller.
* At grade 8, seven states had mathematics gaps in 2007 that were larger than the national gap of 31 points, while 12 had gaps that were smaller.
State Black-White Achievement Gaps—Reading
* At the state level, gaps in grade 4 reading existed in 2007 in the 44 states for which results were available. Gaps narrowed from 1992 to 2007 in Delaware, Florida, and New Jersey, due to larger increases in Black students’ scores.
* At grade 8, reading gaps existed in 2007 in 41 of the 42 states for which results were available. In Hawaii, the 7-point difference between Black and White students’ scores in 2007 was not statistically significant, and thus there was no gap for Hawaii. There was no significant change in the gap in any state from 1998 to 2007.
* At grade 4, eight states had reading gaps that were larger than the 2007 national gap of 27 points, while nine had gaps that were smaller.
* At grade 8, one state had a reading gap that was larger than the 2007 national gap of 26 points, while nine had gaps that were smaller.
The NAEP reading and mathematics scales make it possible to examine relationships between students’ performance and various background factors measured by NAEP, such as race. However, a relationship that exists between achievement and another variable does not reveal its underlying cause, which may be influenced by a number of other variables. Similarly, the assessments do not reflect the influence of unmeasured variables. At the state level, changes in the size of the achievement gap between Black and White students could be affected by demographic changes in the size and makeup of the populations involved, as well as policy changes in the schools and communities. The results of this study are most useful when they are considered in combination with other knowledge about the student population and the education system, such as trends in instruction, changes in the school-age population, and societal demands and expectations.
This report focuses on the size of the achievement gap between Black and White students and the direction of average scores within states, regardless of the states’ scores. Large gaps may occur in some states with scores above the national average, as well as in states with scores below the national average. Similarly, small gaps may occur in states with scores above or below the national average. All differences discussed in this report are statistically significant at the .05 level after controlling for multiple comparisons. The technical notes for this report provide information about sampling, accommodations, interpreting statistical significance, and other technical features. For more information on both the main NAEP and long-term trend assessments, see appendix A.
Complete report: http://nces.ed.gov/nationsreportcard/pdf/studies/2009455.pdf
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