Such high rates of academic underachievement and failure among children with ADHD may result from a number of causes, one of which is likely to be chronic inattention. David Rabiner and colleagues (2000) reported on a large study of children monitored from kindergarten through fifth grade. They found that children identified by their teachers in kindergarten as being more inattentive than most others in their class had significantly lower reading achievement when they reached fifth grade. The problems of these low-achieving children were based on their significant impairments in sustaining attention, not on behavioral difficulties, IQ, or prior reading achievement. From their six-year study the researchers concluded:
About one third of the children who were reading in the normal range after kindergarten, but who were highly inattentive during first grade, had fifth grade reading outcomes more than one SD
[standard deviation] below their peer group. . .. Because first grade is a critical time for the acquisition of early reading skills, one plausible hypothesis is that attention problems interfere with the acquisition of these skills and that it is difficult for children to "catch up." (p. 866)
There are several ways in which learning to read can be problematic for a child. One is a persisting difficulty in recognizing words on the page as words one has heard in conversation. This involves the ability to break down unfamiliar words into their component parts. There are just forty-four of these components, phonemes, in the English language; these combinations of letters that represent a specific sound are the building blocks for all spoken and written words in the language. Sally Shaywitz (2003) has described the fundamental importance of phoneme processing in reading:
Before words can be identified, understood, stored in memory, or retrieved from it, they must first be broken down into phonemes by the neural machinery of the brain.. . . Language is a code, and the only code that can be recognized by the language system and activate its machinery is the phonologic code. . . . Overall the child must come to know that the letters he sees on the page represent, or map onto, the sounds he hears when the same word is spoken. (pp. 41-44)
Shaywitz points out that virtually all humans acquire spoken language simply by consistent exposure to their mother tongue, that learning spoken language is relatively effortless and natural, while reading is not. "Reading is an acquired act, an invention of man that must be learned at a conscious level. . . . The key to unraveling it is not so readily apparent and can only be accessed with effort on the part of the beginning reader" (p. 50).
About 80 percent of American children learn how to transform printed symbols into phonetic code without much difficulty, but for the remaining 20 percent, this code-cracking task is much more difficult. These are the individuals who, in varying degrees, are dyslexic. Many of them can be taught to read, but this usually requires alternative approaches and more intensive instruction and practice than is required for most others.
Among individuals with ADHD there is a markedly elevated incidence of dyslexia (Tannock and Brown 2000). As was shown in the Ra-biner study, attentional problems and other impairments of the ADD syndrome can severely impair an individual's ability to read.
Yet phonemic decoding is not the only element involved in reading; gradually the child needs also to develop fluency and comprehension of longer stretches of text. Virginia Berninger and Todd Richards (2002) described the development of two types of fluency:
The first kind is oral reading fluency in which children not only become faster in recognizing words, but their oral reading begins to reflect the melody or intonation of the spoken language. The second kind is silent reading fluency in which children quickly and automatically access . . . word forms . . . thereby freeing up limited working memory resources for reading comprehension. (pp. 162-163)
Children who suffer from chronic impairments in their ability to sustain attention and effort, to utilize working memory, and to employ other executive functions usually impaired by ADD syndrome, are likely to have continuing difficulty in these more advanced aspects of reading comprehension.
In our Yale Clinic for Attention and Related Disorders, Donald Quin-lan and I administered reading tests to older adolescents and adults diagnosed with ADHD. Their ability to recognize and correctly pronounce lists of words on the Woodcock Johnson Achievement Test was in the high average range. But their scores for demonstrating comprehension of passages several paragraphs long on the Nelson-Denny Reading Test were significantly (1.5 standard deviations) lower. They were also significantly slower at reading the passages. These preliminary findings suggest that adolescents and adults with ADHD are likely to have persisting problems with reading fluency and comprehension that are not explained by poor decoding skills. These findings also indicate that reading problems associated with ADD syndrome do not disappear over time.
Children with significant attention impairments during their early school years are likely to experience difficulties not only in reading, but also in learning mathematics. Elizabeth Benedetto-Nasho and Rosemary Tannock (1999) studied students aged seven to eleven years, half of them with an ADHD diagnosis, half without. The two groups of students were matched for equal math skills and none had any learning disability. When asked to complete sets of math problems appropriate for their ability level, the ADHD students attempted fewer problems, were three times less effective in solving the problems, and made six times as many errors when doing subtraction problems. Errors in subtraction were mostly errors in borrowing; for example, 120 — 9. Such difficulties are likely to involve not only attention to details (for example, noticing whether one is supposed to add, subtract, multiply, or divide), but also working memory functions (such as keeping in mind that one has "borrowed" from the tens column when one subtracts from the ones column).
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