The NICHD Research Program in Reading Development,
Reading Disorders and Reading Instruction
G. Reid Lyon, Ph.D.
Chief, Child Development and Behavior Branch
National Institute of Child Health and Human Development
National Institutes of Health
Background and Purpose
How Do Children
Learn to Read?
Why Do Some Children and Adults Have
Difficulties Learning to Read?
How Can We Help Most Children Learn to Read?
Learning to read is critical to a child's
(and an adult's) well-being. The child and adult who cannot
read at a comfortable level experience significant difficulties
mastering many types of academic content, are at substantial
risk for failure in school, and are frequently unable to reach
their potential in the vocational and occupational arena.
Unfortunately, the rate of reading failure and illiteracy
are unacceptably high in the United States. Over 40 percent
of fourth grade students performed below basic levels on the
National Assessment of Edu-cational Progress (NAEP) in both
1994 and 1998. Over 10% of fourth grade children could not
even participate in the NAEP due to severe reading difficulties.
Moreover, converging evidence from longitudinal, population-
based data indicate that at least 17 percent to 20 percent
of children have a significant reading disability. A real
crisis revealed in these statistics is the disproportionate
representation of children who are poor, racial minorities,
and non-native speakers of English. However, it is also noteworthy
that large numbers of school-age children from all social
classes, races and ethnic groups have significant difficulties
learning to read. Because reading is so critical to success
in our society, reading failure constitutes not only an educational
problem but also rises to the level of a major public health
Since 1965, the National Institute of Child Health and Human
Development (NICHD), within the National Institutes of Health
(NIH), has conducted and continuously supported research efforts
to address three fundamental questions that must be answered
if reading failure is to be understood and addressed successfully.
These three questions are: (1) How do children learn to read?
What are the critical environmental, experiential, cognitive,
linguistic, genetic, neurobiological, and instructional conditions
that foster reading development? (2) Why do some children
and adults have difficulties learning to read? What specific
cognitive, linguistic, environmental, and instructional factors
impede the development of accurate and fluent reading skills,
and what are the most significant risk factors that predispose
youngsters to reading failure? (3) How can we help most children
learn to read? Specifically, for which children are which
teaching approaches and strategies most beneficial at which
stages of reading development?
To answer these three questions, the NICHD has developed a
research network consisting of 41 research sites in North
America, Europe, and Asia to study reading development, reading
disorders and other learning disabilities, and reading instruction.
During the past 33 years, NICHD scientists have studied the
reading development of 34,501 children and adults. Many studies
have been devoted to understanding normal reading development,
and 21,860 good readers have participated in these investigations,
many for as long as 12 years. Significant efforts have also
been deployed to understand why many children do not learn
to read. Within this context, 12,641 individuals with reading
difficulties have been studied, many for as long as 12 years.
In addition, since 1985, the NICHD has initiated studies designed
to develop early identification methods that can recognize
those children during kindergarten and first-grade who are
most at-risk for reading failure. These studies have provided
the foundation for several longitudinal prevention and early
intervention projects now underway at 11 sites in the U.S.
and Canada. Since 1985, 7,669 children (including 1,423 good
readers) have participated in these reading prevention, early
intervention, and remediation studies, and 3,600 children
are currently enrolled in longitudinal intervention trials
in Texas, Washington, DC, Georgia, Massachusetts, New York,
Florida, Colorado, North Carolina, and the state of Washington.
These studies involve the participation of 1,012 classroom
teachers, working in 266 schools and 985 classrooms.
The purpose of this report is to synthesize the major converging
findings that have been obtained by NICHD scientists for each
of the three questions that have guided the reading research
program. This synthesis is derived from an analysis of over
2,500 publications generated by NICHD scientists since 1965.
Evidence and Findings Relevant to Each Major Research Question:
How Do Children Learn to Read?
Evidence and Findings
- Reading is not a natural process. In
contrast to oral language development, reading does not
emerge naturally from interactions with parents and other
adults, even in print-rich environments. For most children,
reading requires systematic and explicit instruction, although
the degree of explicitness, directiveness, intensity and
duration of instruction requires developing specific reading
components that would vary across children.
- Learning to read is a relatively lengthy
process that begins very early in children's development
and substantially before they enter formal schooling. There
is a strong and critical relationship between the amount
and quality of early language and literacy interactions
and experiences and the acquisition of the linguistic skills
necessary for reading. Moreover, frequent language and literacy
interactions from birth onward serve to aid in the development
of oral vocabulary, an awareness of print and literacy concepts,
and an understanding of the goals of reading. Exposure to
oral reading and language play (e.g., rhyming) has been
found to serve a foundational role in the development of
- Reading development requires the acquisition
of phonemic awareness and other phonological processing
skills. Specifically, a necessary foundational skill that
beginning readers must master is that the words and syllables
that they hear via oral language are composed of small units
of sound, termed phonemes.
aware of the sound structure (phonemes) within syllables
and words is made difficult because unlike writing,
when communicating orally, the separate sounds composing
an utterance cannot be "heard" by the ear due to a
process termed co-articulation. Specifically, when
producing speech orally, as in saying the word cat,
only one sound is heard, not three, as in c/a/t. The vocal
apparatus merges the three sounds to permit rapid communication,
and it is the brain, not the ear that recovers the
sound segments from the acoustic bundle. In essence,
to learn to read, the individual must discover that
spoken words can be segmented into smaller units of
sound, that letters on the page represent these sounds,
and that written words have the same number and sequence
of sounds heard in a spoken word.
- As noted above, the beginning reader
must be able to translate print to speech. In an alphabetic
language, like English, the individual letters on a page
are initially abstract and meaningless optical units. These
optical shapes must eventually be linked to sounds - the
phonemes discussed above. In essence, the beginning reader
must learn the connections between the 26 letters of the
alphabet and the approximately 44 English-language phonemes.
The understanding that written spellings systematically
represent the phonemes of spoken words is termed "the
alphabetic principle" and is absolutely necessary for
the development of accurate and rapid decoding and word
reading skills. The development of sound-symbol relationships
is also frequently termed "phonics."
- Although the development of phoneme awareness
and the alphabetic principle are necessary to learn to read,
these skills, in and of themselves, are not sufficient.
Specifically, in order for the novice reader to begin to
devote more attention and memory capacity to the text that
is being read for strong comprehension to occur, phonological
and decoding skills must be applied accurately, fluently
and automatically. Laborious application of decoding and
word recognition skills while reading text reduces attentional
and memory resources, thus impeding reading comprehension.
- The ability to understand what has been
read appears to be based on several factors. Children who
comprehend well are able to activate their relevant background
knowledge when reading - they can relate what has been read
to their own experiences and background knowledge. Strong
comprehension abilities are clearly related to oral language
comprehension, which like reading comprehension is also
critically dependent on the acquisition of a robust oral
vocabulary. Individual differences in reading comprehension
also vary with the reader's ability to actively summarize,
clarify, and predict while reading and the ability to employ
syntactical conventions to enhance comprehension.
- The development of phoneme awareness,
the alphabetic principle, word reading accuracy and fluency,
reading vocabulary, and active reading comprehension strategies
are all necessary, but not sufficient in and of themselves,
to produce robust reading capabilities. These reading elements
or components must be exquisitely integrated via informed
instruction and practice.
- Opportunities to learn to read and to
practice the application of reading skills is essential
to developing accuracy and fluency and a strong sight word
vocabulary. In turn, reading practice serves as a major
factor in the continued development of oral vocabulary,
particularly as children move past the third grade.
Do Some Children and Adults Have Difficulties Learning to
Evidence and Findings
Prevalence, Developmental Course,
and Psychometric Characteristics
- NICHD population-based, epidemiological
longitudinal studies indicate that at least 17 percent to
20 percent of the nation's population displays a reading
disability. Thus, at least 10 million children, or 1 child
in 5 will experience significant difficulties learning to
read well enough to utilize reading to learn and for enjoyment.
Non-NICHD prevalence studies and assessments (e.g., NAEP)
place reading failure at higher levels ranging from 20 percent
in some states to 59 percent in others.
- While public schools identify approximately
four times as many boys as girls as reading disabled, NICHD
longitudinal and epidemiological studies show that as many
girls as boys have difficulties learning to read.
- Reading disabilities typically persist
throughout childhood, adolescence, and adulthood. Difficulties
learning to read do not reflect a transient developmental
lag. NICHD longitudinal studies indicate that of children
who are reading disabled in the third grade, 74 percent
remain disabled at the end of high school.
Distinguishing between disabled readers
with an IQ-reading achievement discrepancy and those without
a discrepancy reflects an invalid practice at the beginning
stages of reading. Specifically, children with and without
a discrepancy do not differ in the information processing
skills (phonological and orthographic coding) that are necessary
for the accurate and rapid reading of single words. Likewise,
genetic and neurophysiological (functional MRI) studies have
not indicated differential etiologies for reading disabled
children with and without discrepancies. Converging data from
several NICHD sites also indicates that the presence and magnitude
of IQ-reading achievement discrepancies are not related significantly
to a child's response to intervention.
- Children with reading disabilities differ
from one another and from other good readers along a continuous
distribution, and do not aggregate together in a distinct
"hump" at the tail of the distribution. Reading
disabilities reflect dimensional rather than categorical
Environmental, Experiential, and
Individual Difference Factors
- Children most at-risk for reading failure
are those who enter school with limited exposure to the
English language and who have little prior understanding
of concepts related to phonemic sensitivity, letter knowledge,
print awareness, the purposes of reading, and oral language
and verbal skills, including vocabulary. Children raised
in poverty, youngsters with limited proficiency in English,
children with speech and hearing impairments, and children
from homes where the parent's or caretaker's reading levels
are low are relatively predisposed to difficulties learning
to read. Likewise, youngsters with sub-average intellectual
capabilities frequently manifest greater difficulties in
most frequent characteristic observed among children
and adults with reading disabilities is a slow, labored
approach to decoding or "sounding-out" unknown or unfamiliar
words and frequent misidentification of familiar words.
Oral reading is hesitant and characterized by frequent
starts and stops and multiple mispronunciations.
- One of the most powerful predictors of
reading comprehension abilities is the speed and accuracy
of reading single words. Likewise, one of the most powerful
predictors of speed and accuracy in reading single words
is the strength of phonemic awareness skill development.
- In contrast to good readers who have
discovered that letters and letter patterns represent segmented
units of sound (phonemes), poor readers have substantial
difficulty developing this principle. As noted in the discussion
of reading development, the major factor impeding the development
of the alphabetic principle and thus decoding and word reading
skills is a lack of facility in phonemic awareness.
- Phonemic awareness skills assessed in
kindergarten, in combination with assessment of the child's
ability to provide letter and number names and letter sounds,
are strong predictors of difficulties learning to read.
Deficits in phoneme awareness skills impact the ability
to develop accurate and fluent word reading capabilities
which significantly degrade comprehension of what has been
- In addition to being negatively affected
by phonological and word level deficits, reading comprehension
is impeded by, among other factors: (1) vocabulary deficits;
(2) inadequate background knowledge relevant to the information
presented in text; (3) lack of familiarity with semantic
and syntactic structures that can be employed to predict
and better understand word and grammatical relationships;
(4) lack of knowledge about different writing conventions
that are employed by the author to achieve different purposes
via text (humor, explanation, dialogue, etc.); (5) lack
of verbal reasoning ability which enables the reader to
"read between the lines"; and (6) the ability
to remember and/or recall verbal information.
- Motivational factors are clearly relevant
to reading development and reading disorders, given that
the improvement a disabled reader may make in learning to
read is highly related to their willingness to persist despite
difficulties. Unfortunately, little is specifically known
about the exact timing and course of motivational influences
in reading development.
- There is strong converging evidence for
a genetic cause of some types of reading disability with
deficits in phonemic awareness being the greatest hereditary
factor. Family history is one of the most important risk
factors, with 23 to as much as 65 percent of children who
have a parent with reading disability having the same difficulties.
A rate among siblings of affected persons of approximately
40 percent and among parents ranging from 27 to 49 percent
provides opportunities for early identification.
- Converging evidence suggests that at
least one type of reading disability can be linked to the
HLA region of chromosome 6 reflecting a possible association
with autoimmune disorders. Evidence obtained from twin and
kindred siblings with severe deficits in reading performance
support a Quantitative Trait Locus on chromosome 6. Chromosome
15 has recently been linked to individual differences in
word reading skills.
- Phonemic awareness and word reading deficits
can also result from a lack of oral language and literacy
exposure and interactions following birth and through the
preschool years. If children are not provided opportunities
to listen to and interact with language in multiple contexts,
their background knowledge about sounds, print concepts,
and vocabulary concepts will be negatively affected. Whether
or not limited oral language exposure is reflected in differences
in neural development during the early years is not yet
- A range of neurobiological investigations
employing post-mortem brain specimens, brain morphometry,
functional brain imaging, and electrophysiology suggests
there are differences in the temporo-parieto-occipital neural
regions between some individuals with reading disability
and those who are not reading-impaired. Additional studies
suggest differences in the striate or extrastriate cortex,
converging with a large body of literature describing anatomical
lesions in posterior brain regions in acquired alexia, most
prominently located in the angular gyrus.
Can We Help Most Children Learn to Read?
Specifically, for Which Children Are Which Teaching Approaches
and Strategies Most Beneficial at Which Stages of Reading
Evidence and Findings
- A massive effort must be undertaken to
inform parents and caretakers of the importance of providing
oral language and literacy experiences from the first days
of life - to engage children in playing with language through
nursery rhymes, storybooks, and as they mature, early writing
activities. Parents and caretakers must become intimately
aware of the importance of vocabulary development and must
interact verbally with their children to enhance verbal
reasoning, semantic, and syntactical abilities.
- Reading out loud to children is a proven
activity for developing vocabulary and language expansion
characteristics, and plays an important role in developing
receptive and expressive language skills. Reading out loud
to children can also help to enhance children's background
knowledge of new concepts that will appear in both oral
and written language.
- NICHD prevention and early intervention
studies continue to provide converging evidence on the importance
of developing accurate and fluent word reading skills, given
the significant importance of such skills in developing
reading comprehension abilities.
- Prevention and early intervention studies
in Tallahassee, Gainesville, Syracuse, Albany, Houston,
Seattle, and Washington, DC are providing converging evidence
that for those children who are at risk for reading failure,
highly direct and systematic instruction to develop phoneme
awareness and phonics skills, reading fluency and automaticity,
and reading comprehension strategies within a literature-rich
environment will be required to obtain maximum gains. It
is also imperative that each of these reading components
be taught within an integrated context and that ample practice
in reading familiar material be afforded to enhance fluency
and automaticity. Likewise, the most effective interventions
provide ample opportunities to read and discuss authentic
- NICHD and substantial non-NICHD research
does not support the claim that the use of context is a
proxy for applying decoding strategies to unknown or unfamilar
words. To guess the pronunciation of words from context,
the context must predict the words. But content words -
the most important words for text comprehension - can be
predicted only 10 to 20 percent of the time. Instead, the
strategy of choice among well developing good readers is
to decode letters to sound in an increasingly complete and
accurate manner, which is dependent upon robust development
of phonemic and phonics skills.
- Without a doubt, early identification
and intervention is essential to maximizing treatment success
in children who are at risk for reading failure. NICHD studies
have led to the development of accurate and reliable identification
procedures that are linked to prevention programs. NICHD
studies have clearly demonstrated that the intensity and
duration of reading interventions must increase exponentially
as children get older just to achieve the same degree of
improvement attainable during kindergarten and the first
- One factor that impedes effective instruction
with children at risk for reading failure is current teacher
preparation practices. Many teachers have not had the opportunity
to develop basic knowledge about the structure of the English
language, reading development, and the nature of reading
difficulties. Major efforts must be undertaken to ensure
that colleges of education develop preparation programs
to foster the necessary content and pedagogical expertise
at both preservice and inservice levels.
This document was prepared for the Keys
to Successful Learning Summit held in May 1999 in
Washington, D.C. Keys to Successful Learning is an ongoing collaboration sponsored by the National Center
for Learning Disabilities in partnership with the Office of
Special Education Programs (US Department of Education) and
the National Institute of Child Health & Human Development
(National Institutes of Health).
The purpose of this initiative is to translate research and
policy on learning disabilities into high standards for learning
and achievement in the classroom, and to take action at the
local, state and federal levels to ensure that all students,
including those with learning disabilities, are afforded the
highest quality education.
Keys to Successful Learning is supported
by a coalition of national and regional funders as well as
a broad range of participating education organizations.