Developmental dyslexia: a computer based diagnostic test

Bruno Morchio*, Michela Ott*, Elia Pesenti"*, Mauro Tavella*

*Istituto Tecnologie Didattiche (ITD)-Consiglio Nazionale delle Ricerche-Genova, Italy (Institute of Educational Technology) (National Research Council) **USL 12 Genova- Italy (Public Health Unit n. 12)

ABSTRACT

Information Technology can play a major role in the diagnosis of developmental dyslexia. This contribution shows the results of a computer based reading test aimed at identifying subjects presenting specific developmental disorders in the reading area. The test, administered to about 1000 Italian students from third to sixth grade, consisted of the timed presentation of one list of words and one list of pronounceable non-words: phonological and visual abilities were thus investigated. Main considerations arising from the analysis of the test's results are:

the test is able to identify subjects with reading disorders in that their performance is significantly poor;

the test can probably be considered as a tool suitable for identifying the specificity of the problems of each child (typology and seriousness of the impairment) in that the performances of subjects showing specific difficulties are qualitatively very· different (presently this point is still under investigation).

In addition the resulting data shows that the performance in the reading of words and non-words is different at any school level (words are always read better than non-words) and that children at the various school levels perform differently: the level of both performances (reading of words and non-words) as well as the difference between them changes with the school level.

THE RESEARCH A computer programme called "Tachistoscopio", that allows the timed presentation of words and small sentences, has been produced within a research program on developmental dyslexia carried out at ITD (B. Morchio, et al., 1989). The program was conceived as a rehabilitative tool to improve reading skills and to exercise the short-term memory, but, above all, as a diagnostic tool to verify the efficiency of different reading strategies. This paper presents the results of a wide experimentation (a total of 992children from various regions of Italy) carried out during the 1988-1989 and 1989-1990 scholastic years in lower and upper primary schools.

OBJECTIVES OF THE EXPERIMENT The main objectives of the experiment were to:

identify normative data on the reading of words and non-words according to different ages and different schools levels, in order to be able to identify poor readers;

analyze how the different modes of simultaneous (visual) and sequential (phonological) reading are structured and developed at various school levels.

Another objective of significant importance to the research as a whole was tocreate a legacy of data that would permit subsequent in-depth qualitative analyses of the different types of reading errors.

THEORETICAL ASSUMPTIONS The test was constructed referring to the 'two routes' standard theoretical model (Fig. 1), for the reading of isolated words generally adopted to explain acquired pathological reading and writing disorders (Marshall, 1984; Patterson, 1986; Sartori, 1984). Our group has been using this cognitive model as a base, to also investigate developmental reading and writing disorders, following also Frith's three stage theory (Frith 1984; 1985).

On this theoretical basis the tachistoscopic presentation of words and nonwords was considered to be a useful way of verifying the habits in the use of the two routes, their relative efficiency and the way they are structured progressivelyin subjects who are in the acquisition phase of reading and writing codes. Words can be read using both the phonological and visual routes relatively independently, or a combination of both, but below certain time thresholds, the reading of words cannot be anything but prevalently visual (words 'read' as a global unit) since sequential and phonological process requires a longer processing (Aaron, 1982; 1989; Valle Arroyo, 1984; 1989). A test based on these assumptions, comprising the reading of two lists, one of words the other of non-words, was developed. The items in the two lists were chosen for their similarity and homogeneousness in order to obtain a resultant picture as close as possible to the actual reading modes and specific abilities and disabilities relative to the two

different proposed tasks: visual reading (words presented rapidly) versus phonological reading (non-words).

THE TEST Characteristic of the list

The test consists in the 'filtered' administration (see section, The presentation of items below) of two lists, one of words, the other of non-words. Both of the lists contain twenty items, each comprising six letters. The length of words was determined by the fact that it is possible to read them all at one eye fixation (Job, 1987; Rayner, 1986). The number of twenty words was chosen as an optimum number for reasons of economy and ease of administration, but at the same time to provide a sufficient sample. Criteria for the choice of words The twenty words were chosen from the 2,000 words most frequently used in Italian. In

grammatical terms they are all nouns (only the word vicino (near) is actually an adjective, but whose use as a noun has become very frequent in Italian). The list was divided into the following:

5 'easy' words composed of a sequence of CV (consonant and vowel) containing no particular orthographic difficulties

10 words with one of the following difficulties: c, g combinations (soft and hard c and g); z; digraphs: gn, eh, gh, gl; cu, qu; double letters; double consonants; triple consonants; non-diphthong vowel groups

5 words with more than one orthographic difficulty Each of the twenty words begins with a different letter of the alphabet, two of them begin

with the letter s (there are no words beginning with h in that there are no such words in

Italian, nor z in that there are no nouns of six letters among the 2000 most used words in

Italian; two words beginning with s were chosen because they are more numerous). Orthographic difficulties occur at various points in the words: at the beginning, in the middle and at the end. The twenty words are divided equally into words of two and three syllables. Eleven of them are masculine, nine are feminine.

Criteria for the choice of non-words Like the words, the non-words are all six letters and pronounceable. They were formed by taking the corresponding word from the preceding list and substituting two letters (with the exception of enchea which was formed from unghia by substituting two vowels and a consonant). That is, the resulting letter combination is different but contains the same kind of orthographic difficulty occurring in the same position in the \\·ord; the number of syllables is the same.

The presentation of items The two lists are presented one after the other in a fixed order: first the list of words and then that of non-words. Each list is presented four times with the stimulus remaining on the screen for different lengths of time each time, starting from the shortest to the longest (60 milliseconds, 100 msecs, 300 msecs and 500 msecs). When a word is read correctly it does not appear in the next round. 'Masking' is used ensure that the time of appearance on the screen is accurate. Therefore when the stimulus disappears, a series of characters (@@@@@) are superimposed on the letters of the word. Thus the image of the word does not remain on the phosphorus of the screen and so lengthen the actual appearance time. The symbol (@) was chosen as its characteristics are balanced graphically compared to those of a letter in order to sufficiently mask it. The order of presentation of the words is fixed and every word is presignalled by a dot in the centre of the screen. Data was collected by specially trained operators. The child is asked to respond to the stimulus orally, and the response is then faithfully transcribed by the operator present. This method was chosen in order to be able to evaluate exactly any reading errors without the interference of 'writing' problems. The type of error can therefore be registered so that both a quantitative and qualitative assessment can subsequently be made. Subjects are not told whether their responses are correct or incorrect. Prior to the administration of the list of words, the child is only told that he/she will see a list of meaningful words, and before the list of non-words that he/she will see a list of invented not meaningful 'words' .

Before each list eight example items are presented, however in this case they appear for ever decreasing amounts of time (500, 400, 300, 200, 100, 60, 45 and 30 millisecs).

The sample The test was administered during the 1988-1989, 1989-1990 scholastic years to three primary classes (3rd, 4th and 5th grade) and to the first year of 'scuola media' (6th grade) of several schools in Bologna, Genoa, Milan and Siena. On the whole the experiment involved 992 children belonging to four grades:

Two Cornoldi's reading tests (Test of Reading Comprehension, Test of Reading Rapidity and Correctness, 1981) were administered to a large portion of the 6th grade sample (300 out of 463) in order to analyse the correlation of this nationwide standardized test with our Word and Non-Word Reading Test. A group of about 25 6th grade very low-achievers was further examined, through clinical individual neuropsychological assessment, in order to better understand the relationship between poor performance in our test and their profile of reading and writing impairment. Since these last two points are presently under final investigation, here we present only part of the data related to these low-achievers.

THE RESULTS Here we present the results of the large sample examined and some profiles of poor readers. Table 1 and 2 show the percentile distributions of the performances in the two tests (Words and Non-Words) at the four school levels (3rd, 4th, 5th and 6th grade), at the different exposure times (60, 100, 300 and 500 milliseconds). We have considered the performances between the 25° and the 75° percentile as "normal"; in the two tables the area of normal performance is shown in bold characters. We consider the performances below the 25° percentile as "poor" and suggest that subjects under this score be referred to further assessment. Clinical validation of the test is present in progress; so far we observed that children with normal IQ, scoring below the 10° percentile at one or both subtest present specific reading disorders whose typologies and seriousness are now under investigation as well as the reading behavior or the normal subjects. In Figures 1-4 the graphs show the frequency distributions of the performances in the two tests (Words and Non-Words) and the differences between them, at the various school levels. In Tables 3 and 4 the average, probable error and lower and upper limits of the range of normal difference between words and non-words are presented.

In Figure 5 the graphs show the different poor performances of two sixth-graders with reading and writing disorders. Briefly, the data shows:

the different performances at the various school levels both for words and non-words;

the different performances in the reading of words compared to non-words within the same grade at the various school levels;

that the differences between the two performances (Words and Non- Words) at the various school levels change inversely to the exposure time;

In addition the data shows the significantly poor performance of children with specific reading difficulties.

In the bold area the performances between the 25Q and the 75° centile are shown.

DIFFERENT PERFORMANCES AT THE VARIOUS SCHOOL LEVELS Tables 1 and 2 show that the abilities of reading either words or non-words are correlated to the school level: younger children present the worst performances at any exposure time. The largest differences between school levels are observed, as expected, at the shortest exposure times (60 and 100 msecs), which proved to be the most selective subtests. As the school level increases, the range of normal performance shifts towards higher scores both within the same exposure time and across successive exposure times, and progressively narrows, and as far as words are concerned, presents a "ceiling" effect at 500 msecs for older students. Conversely, for non-words, at 60 msecs, the test seems to present a "threshold" effect, with poor performances at any school level. The four different school levels are differentiated from each other, for both words and non-words, and under the different exposure time conditions. The range of normal performance for younger children is wider than that of older children at all exposure times, except at the shortest (60 msecs). The 3rd grade performances are always more clearly differentiated and further apart from the other school levels whose performances are closer together. It seems that there is a 11 jump" in reading ability, both of words and non-words, from the 3rd to the 4th grade and that, from there on, reading ability is more likely to be the same, since the differences we observed are smaller. Only a few results of the 5th grade seem to differ from the normal trend of differentiation: at the two longest exposure times, for words, and at the two shortest exposure times, for non-words, the 5th grade's results are just like the 4th grade's. Together they differ slightly both between the previous and the next school level, but do not differentiate between each other. We are tempted to explain this phenomenon as a "plateau" in the reading ability at these two school levels, under those exposure time conditions, rather than due to the sample size (the sample of the 5th grade level is smaller than the others).

Anyway, we are now collecting further 5th grade level data to clarify this point. As exposure time increases the test is less selective and at 500 msecs it differentiates only the 3rd graders, for words, while, in the case of non-words, it maintains its capacity to differentiate even at this low speed.

Different performances in the reading of words and non-words Figures 1-4 show that there is a significant difference between the reading performances of words and non-words at the different exposure times and at any school levels. The largest differences are observed, for all the four school levels, at 100 msecs, which proved to be the most reliable subtest, and which does not show any ceiling or threshold effect. Words are always read better than non-words and this result represents a trend which raises as school level increases at the two shortest exposure times, conversely it decreases from 300 msecs on (see Tables 3 and 4) for older students. The data shows that the ability of reading words better than non-words is correlated to the school level: 3rd grade children present the closest performances, that is the narrowest differences at the shortest exposure times (60 and 100 msecs), while older students present the opposite behaviour, with the narrowest differences at the longest exposure times (300 and 500 msecs). This data could stand for different ways of reading word and non-word stimuli: older students seem to be able to read much more words than non-words at the shortest exposure times (60 and 100 msecs) because they presumably adopt a global-lexical strategy of reading, which cannot be applied to non-word stimuli and which younger children haven't yet developed. Further investigations are obviously necessary to confirm this hypothesis, starting from the study of the qualitative analysis of errors. Significantly poor performances of children with specific reading difficulties In the following graphs (Figure 5) the different performances of two sixth-graders with reading and writing problems are shown as an example. Their performances are unique and differ from one another, although both are significantly poor.

Research is still in progress to analyze the relationship between the patterns of the test results and the type of reading impairment presented by each subject.

CONCLUSIONS The global results of the test are still under investigation mainly as far as the qualitative analysis of the errors and the possibility of identifying the specificity of the impairment are concerned. Nevertheless the test proved to be a suitable tool in order to identify subjects with reading impairments who should therefore be submitted to further clinical examinations. It seems worth while continuing with this kind of research because of the encouraging results, wide implications and, primarily because of the lack of specific nation-wide standardized assessment tools for the Italian language (Morchio et Al. 1989 I b). No such diagnostic instrument, based on Information Technology, had been used before in Italian schools and its impact can easily be considered excellent both with students and teachers: it therefore appears to open up new perspectives and good working possibilities in the field. Moreover our research work has presented interesting data as far as the different modes of simultaneous (visual) and sequential (phonological) reading are concerned, on how they appear to be structured and developed at various school levels. Though this point needs further experimental research work, and it cannot at all be considered exhaustively investigated in this paper, we think our data represents a first contribution.

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