Contents:
A Note About the NICHD Research Program
How the NICHD Research Program is Different
Developing a New Understanding of Reading Difficulties
Research on Treatment for Reading Difficulties
Major Implications for Early Reading Instruction
Other Important Research Questions and Findings
Future Directions
References

The National Institute of Child Health and Development (NICHD) educational research program, initiated in 1965, began to focus more on reading difficulties as it became clear how extensive the reading problem was in the general population. The 1985 Health Research Extension Act resulted in a new charge to the NICHD to improve the quality of reading research by conducting long-term, prospective, longitudinal, and multidisciplinary research. Reid Lyon led the new charge by closely coordinating the work of over 100 researchers in medicine, psychology, and education in approximately 14 different research centers. (Numbers vary from year to year.)

A major problem with reading research in the past was that findings often did not replicate. One researcher would get one result, another researcher would get the opposite result. Lyon and colleagues identified that the key problem in obtaining replicability was that researchers were studying different samples of children. Lyon established detailed sampling requirements for the research and increased scientific rigor in other areas. Consequently, the NICHD research program has produced a growing body of highly replicable findings in the area of early reading acquisition and reading disabilities that have been reported in over 2,000 refereed journal articles since 1965.

To appreciate fully the significance of the NICHD findings it helps to understand the level of scientific rigor used to guide the formation of conclusions from the research. Reid Lyon coordinates the parallel investigation of similar questions across several NICHD research centers. Under Lyon's leadership, the researchers determine that the questions have been answered only when the findings replicate across researchers and settings. Findings with a high degree of replicability are finally considered incontrovertible findings and then form the basis for additional research questions. Funding is awarded the research centers through a competitive peer review process. A panel of researchers who are not competing for the research funds award the funds after evaluating competing proposals according to specific criteria. Each research study within the NICHD network must follow the most rigorous scientific procedures.

True scientific model. The NICHD studies do not embrace any a priori theory, but test all theories against one another at different points in time. In a true scientific paradigm, theories are tested by doing everything to try to prove the theory incorrect. This contrasts with the usual nature of research in education, where untested hypotheses are often presented as proved theories before any testing has occurred.

Long-term duration. The average length of a study has been 8 years, ranging in length from 3 years to 31 years. In these longitudinal studies, the growth of children from preschool through adulthood has been evaluated. Currently, several large-scale, 5-year longitudinal treatment intervention studies are underway. This longer-term design allows evaluation of the effects of different instructional variables on later reading performance.

Sampling procedures. The sampling procedures ensure that all subgroups in the population (all ethnic groups, a full range of IQ levels, and so on) are included in sufficient numbers to provide a window to the population as a whole and provide information regarding the relationship of reading disabilities to other variability in individuals such as IQ. To evaluate the relationship between IQ and reading disabilities, for example, the research subjects must proportionately sample different IQ bands. Most studies involve around 200 subjects representing variation within specified dimensions. Children who do not speak English have been excluded from the NICHD research samples to this point. After basic reading instruction issues have been resolved for teaching children with some knowledge of English, including bilingual children, the research questions will turn to treatment for children who do not know English and are beginning to learn it as a second language.

Researcher bias. Researcher bias is reduced by the sheer number of people involved in the NICHD program. For example, at only one NICHD-funded research center, the one at Yale University, the following researchers are involved: Jack Fletcher, David Francis, Rafael Kloorman, John Gore, John Halahan, Robert Constable, Leonard Katz, Barbara Foorman, Bonita Blachman, Dorothy Aram, Alvin Liberman, Ken Pugh, Michael Studdert-Kennedy, Donald Shankweiler, Karla Stuebing, Keith Stanovich, Linda Siegel, and Louisa Moats. In addition, researchers at the different NICHD centers communicate frequently regarding their findings, checking each other's data and testing alternative explanations with additional studies.

Contrast with other educational research. The NICHD research program differs from much of the earlier research in its scientific rigor. Table 1 helps illustrate the contrast by summarizing several studies that reported conclusions that conflict with those of the NICHD. The studies in Table 1 are laudable for attempting to evaluate competing theories and were sometimes even two years in duration, quite long as educational studies go. Yet the studies are still too short in duration to evaluate the effects of the different treatments on the children's actual ability to read with understanding. In nearly all of the studies in Table 1 the children never progressed far enough in their reading to use a measure of independent reading comprehension to evaluate their learning. The important question of how different approaches to beginning reading instruction ultimately impact authentic reading remains unanswered in these studies.

Many of the measures used to evaluate the children's learning had no established validity as predictors of reading comprehension. For example, children who used multiple cueing systems or who said they valued understanding more than getting the words right, were given higher scores in many of the studies in Table 1. Whether or not this performance would correlate with later reading performance was not established at the time of the research.

With the NICHD research we now know that the values given the responses on these measures should have been reversed. What was considered desirable performance on miscue analyses actually indicates a poor comprehender, rather than a good comprehender. Children who are poor readers make greater use of two of the three cueing systems, syntax and semantics (context), than good readers. Good readers make greater use of the graphophonic cueing system, as indicated by the fact that they read fluently and accurately without rereading. Readers who get words right are better comprehenders than readers who guess using context to figure out words. Most likely the children who scored highest on these measures would become the poorest readers, based on NICHD studies of good and poor readers.

Even when the skills measured do predict better reading later, such as knowing the names of the letters, teaching children these skills does not necessarily guarantee that these children will be better readers later on. Though many of the studies in Table 1 were over two years duration, the time frame was still too short to see the nature of the impact of the instruction on reading comprehension.

Table 1. Research supporting conclusions that conflict with the NICHD research findings.

*N= number of subjects (Ss) in each treatment group.

In contrast, the NICHD longitudinal treatment studies now in progress are five years in duration and have already used reading comprehension measures to evalute instructional variables in the second year of the studies. In addition, the sample sizes are much larger in the NICHD research studies. For example, the kindergarten study by Foorman and her colleagues (in press) involved 260 kindergarten children. Their first- and second-grade study in eight Title I schools involved 375 subjects. Their special education study of children in the lower 25% involved 113 children with reading disabilities. The study of children in the lower 10% at the Florida Treatment Center involved 180 children (Torgesen et al., in press). The larger samples in the NICHD research included a full range of IQ levels, ethnic groups, and included lower income children. As Table 1 shows, the largest study reporting contradictory conclusions included only 100 subjects. Most of the studies involved much smaller samples.

Much of the recent NICHD research has focused on identifying the nature of reading disabilities and the causes. Using modern neuroimaging technology, medical researchers have identified a unique signature on the brain scans of persons with reading problems. These unique brain scans seem to reflect an inability to work with phonemes in the language. This lack of phonemic awareness seems to be a major obstacle to reading acquisition. Children who are not phonemically aware are not able to segment words and syllables into phonemes. Consequently, they do not develop the ability to decode single words accurately and fluently, an inability that is the distinguishing characteristic of persons with reading disabilities.

About 40% of the population have reading problems severe enough to hinder their enjoyment of reading. These problems are generally not developmental and do not diminish over time, but persist into adulthood without appropriate intervention. Because the percentage is so large, an arbitrary cutoff point of 20% was selected for the purpose of labelling children as disabled in basic reading skills. The difference between a child who has a learning disability in reading and a child who is simply a poor reader is only a difference in the severity of the problem.

The most reliable indicator of a reading disability is an inability to decode single words. Lyon (1994, 1995a) suggests that the best way to determine if this inability is "unexpected" is to compare the performance of a child with that of other children his or her age and / or compare reading ability to academic performance in other domains (e.g., listening comprehension, verbal expression, mathematics, written expression). The definition suggests that traditional methods for identifying a reading disability, such as looking for an IQ-achievement discrepancy, are not as reliable (Lyon, 1994; Lyon, 1995a).

Phonological processing is the primary ability area where children with reading disabilities differ from other children. It does not seem to matter whether the children have an IQ-achievement discrepancy in reading or not. Phonological processing encompasses at least three different components. Each component and a sample assessment are described in Table 2.

Table 2. Three important components of phonological processing and sample assessments.

Component Skill	Assessment
Phonological awareness	E.g., say cat without the /t/ sound.
Phonological recoding in lexical access (Rapid naming)	Name objects, letters, colors quickly.
Phonological recoding in working memory	Repeat sentences, words, or digits accurately.

Of these three major phonological processing skills, phonological awareness appears to be the most prevalent linguistic deficit in disabled readers.

What is Developmentally Appropriate?
Treatment intervention research has shown that appropriate early direct instruction seems to be the best medicine for reading problems. Reading is not developmental or natural, but is learned. Reading disabilities reflect a persistent deficit, rather than a developmental lag in linguistic (phonological) skills and basic reading skills. Children who fall behind at an early age (K and grade 1) fall further and further behind over time. Longitudinal studies show that of the children who are diagnosed as reading disabled in third grade, 74% remain disabled in ninth grade (Fletcher, et al., 1994; Shaywitz, Escobar, Shaywitz, Fletcher, & Makuch, 1992; Stanovich, 1986; Stanovich & Siegel, 1994). Adults with reading problems exhibit the same characteristics that are exhibited by children with reading problems.

These findings contradict the prevalent notion that children will begin to learn to read when they are "ready." The concept "developmentally appropriate" should not suggest delaying intervention, but using appropriate instructional strategies at an early age—especially in kindergarten. Although we now have the ability to identify children who are at-risk for reading failure, and we now understand some of the instructional conditions that must be considered for teaching, the majority of reading disabilities are not identified until the third grade.

Early Identification and Treatment
The best predictor in K or 1st grade of a future reading disability in grade 3 is a combination of performance on measures of phonemic awareness, rapid naming of letters, numbers, and objects, and print awareness. Phonemic awareness is the ability to segment words and syllables into constituent sound units, or phonemes. Converging evidence from all the research centers show that deficits in phonemic awareness reflect the core deficit in reading disabilities. These deficits are characterized by difficulties in segmenting syllables and words into constituent sound units called phonemes—in short, there is a difficulty in turning spelling into sounds.

Lack of phonemic awareness seems to be a major obstacle for learning to read (Vellutino & Scanlon, 1987a; Wagner & Torgeson, 1987). This is true for any language, even Chinese. About 2 in 5 children have some level of difficulty with phonemic awareness. For about 1 in 5 children phonemic awareness does not develop or improve over time. These children never catch up but fall further and further behind in reading and in all academic subjects (Fletcher, et al., 1994; Shaywitz, Escobar, Shaywitz, Fletcher, & Makuch, 1992; Stanovich, 1986; Stanovich & Siegel, 1994).

Instruction using the following types of phonemic awareness tasks has had a positive effect on reading acquisition and spelling for nonreaders: rhyming, auditorily discriminating sounds that are different, blending spoken sounds into words, word-to-word matching, isolating sounds in words, counting phonemes, segmenting spoken words into sounds, deleting sounds from words (Ball & Blachman, 1991; Byrne & Fielding-Barnsley, 1990; Cunningham, 1990; Foorman, Francis, Beeler, Winikates, & Fletcher, in press; Lie, 1991; Lundberg, Frost, & Petersen, 1988; Vellutino & Scanlon, 1987b; Yopp, 1988).

Explicit instruction in how segmentation and blending are involved in the reading process was superior to instruction that did not explicitly teach the children to apply phonemic awareness to reading (Cunningham, 1990). Kindergarten children with explicit instruction in phonemic awareness did better than a group of first graders who had no instruction, indicating that this crucial preskill for reading can be taught at least by age 5 and is not developmental (Cunningham, 1990).

In a study by Ball and Blachman (1991), 7 weeks of explicit instruction in phonemic awareness combined with explicit instruction in sound-spelling correspondences for kindergarten children was more powerful than instruction in sound-spelling correspondences alone and more powerful than language activities in improving reading skills.

In a study by Foorman, Francis, Beerly, Winikates, & Fletcher (in press), 260 children were randomly assigned to a revised kindergarten curriculum (n=80) and a standard curriculum (n=160) consisting of developmentally appropriate practices described by the state of Texas' essential elements for kindergarten. The revised curriculum sought to prevent reading disabilities by teaching phonemic awareness for 15 minutes a day using the Lundberg, Frost, and Petersen (1988) curriculum from Sweden and Denmark. Children in the revised curriculum made significant gains in phonemic awareness over the year. Foorman et al. found that the greatest gains occurred when the explicit instruction moved into teaching the sound-spelling relationships concurrently with the instruction in phonemic awareness.

Explicit, Systematic Instruction in Sound-spelling Correspondences
Phonemic awareness alone is not sufficient for many children. Explicit, systematic instruction in common sound-spelling correspondences is also necessary (Adams, 1988; Ball & Blachman, 1991; Byrne & Fielding-Barnsley, 1990; Foorman et al., in press; Mann, 1993; Rack, Snowling, & Olson, 1992; Snowling, 1991; Spector, 1995; Stanovich, 1986; Torgesen et al., in press; Vellutino, 1991; Vellutino & Scanlon, 1987a). Foorman, Francis, Novy, & Liberman (1991) found that more intensive instruction in sound-spelling relationships during reading (45 minutes per day) was more effective than less daily instruction in sound-spelling relationships (sound-spelling instruction occurring only during spelling and not during reading).

Instruction in specific sound-spelling relationships was more effective than a strategy for using analogous word parts on transfer to new words and on standardized reading measures (Lovett, Borden, DeLuca, Lacerenza, Benson, & Brackstone, 1994). Torgesen et al. (in press) also found that explicitly teaching the sound-spelling relationships was superior to teaching explicitly using word families and word analogies and superior to an implicit approach.

Foorman, Francis, Beerly, Winikates, and Fletcher (in press) found that explicit, systematic instruction in sound-spelling relationships in the classroom was more effective in reducing reading disabilities than a print-rich environment characterized by interesting stories, even with children who had benefited from phonemic awareness instruction in kindergarten.

"[Explicit, systematic instruction in sound-spelling relationships] brought economically disadvantaged, low-achieving first and second graders close to the national average in reading on the Woodcock-Johnson-R, whereas whole language instruction placed these [Title] 1 students near the 25th percentile. Children scoring below the 25th percentile are often identified as reading disabled under traditional diagnostic criteria. These results suggest that [explicit, systematic instruction] in sound-spelling patterns in first and second grade classrooms can prevent reading difficulties in a population of children at-risk of reading failure." (Foorman et al., in press)

Figure 1 graphically displays the effects on reading comprehension for the three treatments Foorman et al. compared. The whole language treatment offered children a print-rich environment with interesting stories. The embedded phonics treatment included a more structured approach to phonics in a print-rich environment. The systematic, explicit phonic approach included phonemic awareness instruction, explicit instruction in sound-spelling relationships, and extensive practice in decodable text. Details of the explicit, systematic approach are described in the next section.

Foorman, Francis, Beeler, Winikates, and Fletcher, in press

Foorman et al. (in press) also found that changing instruction from whole language to explicit, systematic phonics at the classroom level was more effective in reducing the occurrence of reading problems than any of three types of one-on-one tutorial programs that were evaluated. Foorman and her colleagues concluded that in order to avoid reading failure, the focus should be on prevention, not intervention.

"It was the classroom curriculum effect, not the tutorial method effect that was significant. The tutorial effect was not particularly strong, given the weak association between growth in word reading and number of days in tutorial. But at least the tutorial may have kept children from falling further behind in reading. These curriculum effects have important implications for urban school districts with large numbers of students at risk for reading failure. The morbidity of reading failure and subsequent placement in special education can possibly be reduced with explicit, systematic phonics in the alphabetic code during first grade." (p. 16)

"An emphasis on the role of contextual guessing actually represents a classic case of mistaken analogy in science and has been recognized as such for over a decade....It is often incorrectly assumed that predicting upcoming words in sentences is a relatively easy and highly accurate activity. Actually, many different empirical studies have indicated that naturalistic text is not that predictable. Alford (1980) found that for a set of moderately long expository passages of text, subjects needed an average of more than four guesses to correctly anticipate upcoming words in the passage (the method of scoring actually makes this a considerable underestimate). Across a variety of subject populations and texts, a reader's probability of predicting the next word in a passage is usually between .20 and .35 (Aborn, Rubenstein, & Sterling, 1959; Gough, 1983; Miller & Coleman, 1967; Perfetti, Goldman, & Hogaboam, 1979; Rubenstein & Aborn, 1958). Indeed, as Gough (1983) has shown, the figure is highest for function words, and is often quite low for the very words in the passage that carry the most information content." (p. 90)

"The key error of the whole language movement is the assumption that contextual dependency is always associated with good reading. In fact, the word recognition skills of the good reader are so rapid, automatic, and efficient that the skilled reader need not rely on contextual information. In fact, it is poor readers who guess from context-out of necessity because their decoding skillls are so weak." (p. 92)

Below are the key principles of effective reading instruction identified in the research along with concrete examples of what these principles mean. These examples are taken directly from the research studies. The research findings indicate that to prevent reading problems classroom teachers should do the following:

1. Begin teaching phonemic awareness directly at an early age (kindergarten).
Children who are able to recognize individual sounds in words are phonemically aware. Phonemic awareness can be taught with listening and oral reproduction tasks similar to those listed below. When concurrent instruction in sound-spelling relationships occurs, growth in the development of phonemic awareness seems to accelerate. Teachers should initiate instruction in phonemic awareness before beginning instruction in sound-spelling relationships and continue phonemic awareness activities while teaching the sound-spelling relationships.

There is little correlation between developmental stages and phonemic awareness. Every school child is ready for some phonemic instruction. In fact, if the children who fall behind do not begin receiving explicit teacher-initiated instruction, they are very likely to continue falling further and further behind. Phonemic awareness and other important reading skills are learned and do not develop naturally. The earliest direct interventions have been initiated in kindergarten with very positive results. How preschoolers respond to instruction is a question currently under investigation.

2. Teach each sound-spelling correspondence explicitly.
Not all phonic instructional methods are equally effective. Telling the children explicitly what single sound a given letter or letter combination makes is more effective in preventing reading problems than encouraging the child to figure out the sounds for the letters by giving clues. Many children have difficulty figuring out the individual sound-spelling correspondences if they hear them only in the context of words and word parts. Phonemes must be separated from words for instruction.

Explicit instruction means that a phoneme is isolated for the children. For example, the teacher shows the children the letter m and says, "This letter says /mmm/." In this way a new phoneme is introduced. A new phoneme and other phonemes the children have learned should be briefly practiced each day, not in the context of words, but in isolation. These practice sessions need only be about 5 minutes long. The rest of the lesson involves using these same phonemes in the context of words and stories that are composed of only the letter-phoneme relationships the children know at that point.

3. Teach frequent, highly regular sound-spelling relationships systematically.
Only a few sound-spelling relationships are necessary to read. The most effective instructional programs teach children to read successfully with only 40 to 50 sound-spelling relationships. (Writing can require a few more, about 70 sound-spelling relationships.) The chart below is not taken from any particular program but represents the 48 most regular letter-phoneme relationships. (The given sounds for each of the letters and letter groups are either the most frequent sound or occur at least 75% of the time.)

To teach systematically means to coordinate the introduction of the sound-spellings with the material the children are asked to read. The words and stories the children read are composed of only the sound-spelling relationships the children have learned, so all the children must be taught using the same sequence. The order of the introduction of sound-spelling relationships should be planned to allow reading material composed of meaningful words and stories as soon as possible. For example, if the first three sound-spelling relationships the children learn are a, b, c, the only real word the children could read would be cab. However, if the first three sound-spelling relationships were m,a,s, the children could read am, Sam, mass, ma'am.

4. Show children exactly how to sound out words.
After children have learned two or three sound-spelling correspondences, begin teaching them how to blend the sounds into words. Show them how to move sequentially from left to right through spellings as they "sound out," or say the sound for each spelling. Practice blending words composed of only the sound-spelling relationships the children have learned every day.

5. Use connected, decodable text for children to practice the sound-spelling relationships they learn.
The findings of the NICHD research emphasize that children need extensive practice applying their knowledge of sound-spelling relationships to the task of reading as they are learning them. This integration of phonics and reading can only occur with the use of decodable text. Decodable text is composed of words that use the sound-spelling correspondences the children have learned to that point and a limited number of sight words that have been systematically taught. As the children learn more sound-spelling correspondences, the texts become more sophisticated in meaning, but initially they are very limited. Only decodable text provides children the opportunity to practice their new knowledge of sound-letter relationships in the context of connected reading.

Texts that are less decodable do not allow the integration of the phonological knowledge the children gain with actual reading. For example, the first sentence children read in a meaning-based program that added an unintegrated phonic component was: "The dog is up." The sound-letter relationships the children had learned up to this point were: d, m, s, r, and t. This is how much of the sentence the children could read by applying what they had learned in the phonic component: "--- d-- -- --. In this case, it is impossible for the children to use their phonics knowledge to read.

Here is a different example: "Sam sees a big fist." The sounds the children have learned to this point are: a, s, m, b, t, ee, f, g, and i. This is how much of the sentence the children can read using the sound-spelling relationships they have learned: "Sam sees a big fist." This sentence is 100% decodable. Here the children can apply the sound-spelling relationships they have learned to their reading of this sentence, so the phonics component is integrated into the child's real reading. Only decodable text provides children a context for using their new knowledge of sound-spelling relationships in the context of real reading.

Text that is less decodable requires the children to use prediction or context to figure out words. Much research has evaluated the effectiveness of prediction as a strategy for word recognition. Though prediction is valuable in comprehension for predicting the next event or predicting an outcome, the research indicates that it is not useful in word recognition. The following passage is a sample of authentic text (from Jack London). The parts of the text that are omitted are the parts that a child was unable to decode accurately. The child was able to decode approximately 80% of the text. If prediction is a useful strategy, a good reader should be able to read this easily with understanding:

He had never seen dogs fight as these w__ish c___ f___t, and his first ex_______ t_____t him an unf______able l____n. It is true, it was a vi____ ex_______, else he would not have lived to pr_____it by it. Curly was the v_______. They were camped near the log store, where she, in her friend__ way, made ad______ to a husky dog the size of a full-______ wolf, th____ not half so large as _he. __ere was no w____ing, only a leap in like a flash, a met____ clip of teeth, a leap out equal__ swift, and Curly's face was ripped open from eye to jaw.
It was the wolf manner of fight___, to st___ and leap away; but there was more to it than this. Th__ or forty huskies ran _o the spot and not com_____d that s_____t circle. But did not com_____d that s______t in_______, not the e___ way with which they were licking their chops. Curly rushed her ant________, who struck again and leaped aside. He met her next rush with his chest, in a p_______ fash___ that tum__ed her off her feet. She never re_____ed them. This was __at the on_______ing huskies had w______ for.

6. The use of interesting stories to develop language comprehension.
The use of interesting authentic stories to develop language comprehension is not ruled out by this research. Only the use of these stories as reading material for nonreaders is ruled out. Any controlled connected text, whether it is controlled for decodability or for vocabulary, will not be able to provide entire coherent stories in the early stages of reading acquisition. During this early stage of reading acquisition, the children can still benefit from stories that the teacher reads to them. These teacher-read stories can play an important role in building the children's oral language comprehension, which ultimately affects their reading comprehension. These story-based activities should be structured to build comprehension skills, not decoding skills.

Balance, but don't mix. The sixth feature, using real stories to develop comprehension, should be balanced with the decoding instruction described in the first five features. The comprehension instruction and the decoding instruction are separate from each other while children are learning to decode, but both types of instructional activities should occur. In other words, comprehension and decoding instruction should be balanced. A common misconception regarding the balance that is called for by the research is that the teacher should teach sound-spelling relationships in the context of real stories. This mixture of decoding and comprehension instruction in the same instructional activity is clearly less effective, even when the decoding instruction is fairly structured. The inferiority of instructional activities with mixed goals (embedded phonics)had been demonstrated in several studies (Foorman et al., in press; Foorman, Francis, Novy, & Liberman, 1991; Torgesen et al., in press).

During the early stages of reading acquisition, children's oral language comprehension level is much higher than their reading comprehension level. The text material used to build children's comprehension should be geared to their oral language comprehension level. The material used to build their decoding should be geared to their decoding skills, with attention to meaning. Though decodable text can be meaningful and engaging, it will not build children's comprehension skills nor teach them new vocabulary to the extent that might be needed. Comprehension strategies and new vocabulary should be taught using orally presented stories and texts that are more sophisticated than the early decodable text the children read. The teacher should read this text to the children and discuss the meaning with them. After the children become fluent decoders, they can apply these comprehension strategies to their own reading.

The scope of the NICHD research program is much broader than identifying effective methods for treating reading difficulties. Some of these research questions and the findings are briefly described below.

Research Question: Are there medical reasons to explain why 20 to 40% of the population do not naturally develop phonemic awareness?
Finding: Yes, sophisticated modern brain research using neuroimaging and other technologies show a unique brain signature for many, but not all, children without phonemic awareness. This neuroimaging research is being conducted at several NICHD sites, thus providing the opportunity for replication.

Research Question: Are reading disabilities inherited?
Finding: Twin studies have found strong evidence for genetic etiology of reading disability, with deficits in phonemic awareness reflecting the greatest degree of heritability. There is also behavioral genetic evidence for degrees of heritability for letter processing.

Research Question: How does ADD relate to learning disabilities?
Finding: Disorders of attention and reading disabilities often coexist, but the two disorders appear distinct and separable with respect to the effects of attention-deficit disorder (ADD) on cognitive tasks. For example, it has been found that ADD children perform poorly on rote verbal learning and memory tasks, but relatively well on naming and phonemic awareness tasks. The converse appears to be the case for children with reading disabilities.

Research Question: Are more boys than girls reading disabled?
Finding: Despite the widely held belief that boys are more likely to have reading disabilities than girls, research has shown that as many girls as boys have difficulties learning to read. More boys are identified by teachers in school because of their tendency to be more rowdy and active than girls.

The NICHD research program has made a great deal of progress in the investigation of reading disabilities. These findings are potentially of great benefit to most children. However, the work is not done and not all the issues are resolved. There are still some children remaining with reading problems in the most successful interventions described above. Future research will investigate effective treatments for teaching children who have no knowledge of English to read English. The on-going longitudinal intervention studies sponsored by the NICHD will be bringing important new knowledge to the field in the continuing effort to make every child a reader at an early age.

The NICHD Research Sites

Within this context, scientists from NICHD and other scientists as well as leaders from the National Center for Learning Disabilities and the Orton Dyslexia Society Research Committee collaborated to develop an improved definition of disabilities in basic reading skills based on the most recent research in the field. Characterizing the definition as a "working" definition reflects the need to alter the definition in light of continuing advances in research and clinical knowledge. The working definition is as follows:

Dyslexia is one of several distinct learning disabilities. It is a specific language-based disorder of constitutional origin characterized by difficulties in single word decoding, usually reflecting insufficient phonological processing. These difficulties in single word decoding are often unexpected in relation to age and other cognitive and academic abilities; they are not the result of generalized developmental disability or sensory impairment. Dyslexia is manifest by variable difficulty with different forms of language, often including, in addition to problems with reading, a conspicuous problem with acquiring proficiency in writing and spelling (The Orton Dyslexia Society Research Committee, April, 1994).

Alford, J. (1980, May). Predicting predictability: Identification of sources of contextual constraint on words in text. Paper presented at the meeting of the Midwestern Psychological Association, St. Louis.

Aborn, M., Rubenstein, H., & Sterling, F. (1959). Sources of contextual constraint upon words in sentences. Journal of Experimental Pscyhology, 57, 171-180.

Adams, M. (1990). Beginning to read: Thinking and learning about print. Cambridge, MA: MIT Press.

Ball, E. W., & Blachman, B. A. (1991). Does phoneme awareness training in kindergarten make a difference in early word recognition and developmental spelling? Reading Research Quarterly, 26(1), 49-66.

Byrne, B., & Fielding-Barnsley, R. (1990). Acquiring the alphabetic principle: A case for teaching recognition of phoneme identity. Journal of Educational Psychology, 83, 451-455.

Cunningham, A. E. (1990). Explicit versus implicit instruction in phonological awareness. Journal of Experimental Child Psychology, 50, 429-444.

Dahl, K.L., & Freppon, P. (1995). A comparison of inner-city children's interpretations of reading and writing instruction in the early grades in skill-based and whole language classrooms. Reading Research Quarterly, 30, 50-74.

Fletcher, J., Shaywitz, S., Shankweiler, D., Katz, L., Liberman, I., Stuebing, K., Francis, D., Fowler, A., & Shaywitz, B. (1994). Cognitive profiles of reading disability: Comparisons of discrepancy and low achievement definitions. Journal of Educational Psychology, 86(1), 6-23.

Foorman, B., Francis, D., Beeler, T., Winikates, D, & Fletcher, J. (in press). Early interventions for children with reading problems: Study designs and preliminary findings. Learning Disabilities: A Multi-disciplinary Journal.

Foorman, B., Francis, D., Novy, D. & Liberman, D. (1991). How letter-sound instruction mediates progress in first-grade reading and spelling. Journal of Educational Psychology, 83(4), 456-469.

Francis, D., Shaywitz, S., Stuebing, K., Shaywitz, B., & Fletcher, J. (1996). Developmental lag versus deficit models of reading disability: A longitudinal, individual growth curves analysis. Journal of Educational Psychology, 88(1), 3-17.

Freppon, P.A. (1991). Children's concepts of the nature and purpose of reading in different instructional settings. Journal of Reading Behavior, 23(2), 139-163.

Gough, P. (1983). Context, form, and interaction. In K. rayner (Ed.), Eye mevements in reading pp. 331-358). Cambridge, MA: MIT Press.

Hiebert, E. H., Colt, J.M., Catto, S.L., & Gary, E.C. (1992). Reading and writing of first-grade students in a restructured Chapter 1 program. American Educational Research Journal, 29, 545-572.

Iversen, S., & Tunmer, W. (1993). Phonological Processing Skills and the Reading Recovery Program. Journal of Educational Psychology, 85(1), 112-126.

Kasten, W.C., & Clarke, B.K. (1989). Reading / writing readiness for preschool and kindergarten childrne: A whole language approach. Sansibel: Florida Educational Research and Development Council (ED 312 041).

Kaufman, A.S., & Kaufman, N.L. (1985). Kaufman Test of Educational Achievement. Circle Pines, MN: American Guidance Service.

Lie, A. (1991). Effects of a training program for stimulating skills in word analysis in first-grade children. Reading Research Quarterly, 26(3), 234-250.

Lovett, M., Borden, S., DeLuca, T., Lacerenza, L., Benson, N., & Brackstone, D. (1994). Treating core deficits of developmental dyslexia: Evidence of transfer of learning after phonologically- and strategy-based reading training programs. Developmental Psychology, 30(6), 805-822.

Lundberg, I., Frost, J., & Petersen, O. (1988). Effects of an extensive program for stimulating phonological awareness in preschool children. Reading Research Quarterly, 23, 263-284.

Lyon, R., & Alexander, D. (1996). NICHD research program in learning disabilities. In S. Horowitz (Ed.), Their World, p 13-15. New York, NY: National Center for Learning Disabilities.

Lyon, G.R., & Chhabra, V. (1996). The current state of the science and the future of specific reading disability. Mental Retardation and Developmental Disabilities Research Reviews, 2, 2-9.

Lyon, G.R. (1993). Treatment effectiveness for the learning disabled. Request for Applications (93-009). Bethesda, MD: The National Institute of Child Health and Human Development.

Lyon, G.R. (1994). Frames of reference for the assessment of learning disabilities: New views on measurement issues. Baltimore, MD: Paul H. Brookes.

Lyon, G.R. (1995a). Toward a definition of dyslexia. Annals of Dyslexia, 45, 3-27.

Lyon, G.R. (1995b). Research initiatives in learning disabilities: Contributions from scientists supported by the National Institite of Child Health and Human Development. Journal of Child Neurology, 10, 120-126.

Lyon, G.R., Gray, D., Kavanagh, J., Krasnegor, N. (Eds.) (1993). Better understanding learning disabilities: New views from research and their implications for education and public policies. Baltimore, MD: Paul H. Brookes.

Mann, V. A. (1993). Phoneme awareness and future reading ability. Journal of Learning Disabilities, 26(4), 259-269.

McIntyre, E., & Freppon, P. (1994). A comparison of children's development of alphabetic knowledge in a skill-based and a whole language classroom. Research in the Teaching of English, 28, 391-417.

Miller, G., & Coleman, E. (1967). A set of thirty-six prose passages calibrated for complexity. Journal of Verbal Learning and Verbal Behavior, , 851-854.

Perfetti, C.A., Goldman, S., & Hogaboam, T. (1979). Reading skill and the identification of words in discourse context. Memory and Cognition, 7, 273-282.

Rack, J. P., Snowling, M. J., & Olson, R. K. (1992). The nonword reading deficit in developmental dyslexia: A review. Reading Research Quarterly, 27(1), 29-53.

Ribowsky, H. (1985). The effects of a code emphasis approach and a whole language approach upon emergent literacy of kindergarten children. Alexandria, VA: Educational Document Reproduction Service (ED 269 720).

Rubenstein, H., & Aborn, M. (1958). Learning, prediction, and readability. Journal of Applied Psychology, 42, 28-32.

Shaywitz, S., Escobar, M., Shaywitz, B., Fletcher, J., & Makuch, R. (1992). Evidence that dyslexia may represent the lower tail of a normal distribution of reading disability. New England Journal of Medicine, 326(3), 145-150.

Snowling, M. (1991. Dyslexia: A cognitive developmental perspective. Oxford: Basil Blackwell.

Spector, J. E. (1995). Phonemic awareness training: Application of principles of direct instruction. Reading & Writing Quarterly, II, 37-51.

Stanovich, K., & Siegel, L. (1994). Phenotypic performance profile of children with reading disabilities: A regression-based test of the phonological-core variable-difference model. Journal of Educational Psychology, 86(1), 24-53.

Stanovich, K. (1993). The construct validity of discrepancy definitions of reading disability. In G.R. Lyon, D. Gray, J. Kavanagh,, N. Krasnegor (Eds.) (1993). Better understanding learning disabilities: New views from research and their implications for education and public policies. Baltimore, MD: Paul H. Brookes.

Stanovich, K. (1994). Romance and reality. The Reading Teacher, 47(4), 280-291.

Stanovich, K., & Stanovich, P. (1995). How research might inform the debate about early reading acquisition. Journal of Research in Reading, 18(2), 87-105.

Stanovich, K.E. (1986). Matthew effects in reading: Some consequences of individual differences in the acquisition of literacy. Reading Research Quarterly, 21, 360-407.

Stice, C.F., & Bertrand, N.P. (1990). Whole language and the emergent literacy of at-risk children: A two-year study. Nashville: Center of Excellence, Basic Skills, Tennessee State University (ED 324 636).

Torgesen, J.K., Wagner, R., Rashotte, C.A., Alexander, A.W., & Conway, T. (in press). Preventive and remedial interventions for children with severe reading disabilities. Learning Disabilities: A Multidisciplinary Journal.

Vellutino, F. R. (1991). Introduction to three studies on reading acquisition: Convergent findings on theoretical foundations of code-oriented versus whole-language approaches to reading instruction. Journal of Educational Psychology, 83(4), 437-443.

Vellutino, F. R., & Scanlon, D. M. (1987a). Linguistic coding and reading ability. In S. Rosenberg (Ed.), Advances in applied psycholinguistics (pp. 1-69). New York: Cambridge University Press.

Vellutino, F. R., & Scanlon, D. M. (1987b). Phonological coding, phonological awareness, and reading ability: Evidence from a longitudinal and experimental study. Merrill-Palmer Quarterly, 33(3), 321-363.

Wagner, R.K., & Torgesen, J. (1987). The nature of phonological processing and its causal role in the acquisition of reading skills. Psychological Bulletin, 101, 192-212.

Yopp, H. K. (1988). The validity and realiability of phonemic awareness tests. Reading Research Quarterly, 23(2), 159-176.

Reproduced by permission of The National Right to Read Foundation.