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THE DYSLEXIC SCREENING TEST
The DST Test Battery
As discussed above, the battery includes both tests of attainment and diagnostic tests.
Tests of attainment
Three tests are included: reading, writing and spelling. These correspond directly to the accepted difficulties of dyslexic children. Furthermore, since we have designed the tests to assess a composite of fluency and accuracy, the reading and writing tests provide a face-valid assessment of the need for extra time in examinations. The tests have been designed to cause as little anxiety as possible, even for children who know they have reading problems.
Test 3: One Minute Reading. Most tests of reading are intended as stand-alone tests, and take too long to administer for inclusion in the DST. Furthermore, unless speed is measured as well as accuracy, they may well overestimate a dyslexic child's reading performance. Even 'remediated' dyslexic children will tend to read slowly and laboriously. The one minute reading test score is essentially the number of words that the child can read correctly in one minute. It therefore combines fluency and accuracy. The words are graded in terms of reading difficulty:
Test 6: Two Minute Spelling. This has a similar rationale to the One Minute Reading Test, with the words increasing in difficulty of spelling, but in this case the tester reads out each word and the child writes down its spelling, with the tester saying the next word as soon as the child finishes the current one. It is an index of spelling fluency.
Test 9: One Minute Writing. This is essentially an index of speed of copying text, and therefore provides an indication of 'pure' writing speed in the absence of need for thought. Taken together with the Two Minute Spelling Test score, it provides an index of speed of writing taking into account the need to think of spellings.
Taken together, these tests cover the three criterial requirements for difficulty in dyslexia. Furthermore, they can be taken to provide evidence relating to examination concessions for secondary age children. To the authors' knowledge (Autumn 1995) there are not any other tests which provide evidence of spelling fluency (rather than accuracy) or writing speed.
Diagnostic tests
The above attainments tests provide information as to whether a child is struggling with reading, writing and spelling, but not why. The following diagnostic tests cover the range of skills known to be affected in dyslexia, and the profile of difficulties can be used both to interpret the causes of attainment difficulties and also as an index of which skills need support.
Test 1: Rapid Naming. There is strong evidence that dyslexic children are slower than normal to name pictures (or colours), especially when there is a series of stimuli to be named. This test measures the time taken to name a page full of outline drawings, and is based on the 'Rapid Automatised Naming' test discovered by Denckla in the 1970s to be an indicator of dyslexia.
Test 2: Bead Threading. As noted above, motor skill deficits are often associated with dyslexia. This test finds out how many beads the child can thread in 30 seconds - a fine motor skill involving co-ordination of both hands and eye - and has been found to be significantly associated with dyslexia.
Test 4: Postural Stability. One of the most surprising finds in dyslexia research is that dyslexic children suffer from difficulties in balance, especially when they are not concentrating on the balance task. This test has been specially developed to provide an accurate index of balance ability under the disturbance of a controlled push in the back. It appears to be one of the most stable indicators of dyslexia, with a high incidence across the age range. It is also one of the few tests where dyslexic children score worse than non-dyslexic poor readers. Postural stability difficulties are generally considered to reflect some abnormality of the cerebellum.
Test 5: Phonemic Segmentation. Phonological difficulties are an established problem in dyslexia. The test assesses the ability to break down a word into its constituent sounds, and to manipulate those sounds (for example "say 'speak' without the 'p'"). It is likely that this test assesses both phonological skill and working memory.
Test 7: Backwards Digit Span. Digit span tests are a standard component of IQ tests, and one on which dyslexic children are known to perform poorly. They tend to do even worse on Backwards Digit Span (the tester says a sequence of single digits, and the child has to repeat them back in the opposite order), probably because the child must manipulate the remembered string of digits in working memory before repeating them back. Backwards Digit Span is therefore a test of how well the children can use their working memory.
Test 8: Nonsense Passage Reading. There is considerable evidence that even when dyslexic children score adequately on standard tests of reading, they continue to have difficulty reading words with which they are not familiar. This test assesses this skill by mixing nonsense words with real words in a nonsense passage (like Lewis Carroll's 'Jabberwock' poem). Specific difficulties reading nonsense words indicate difficulties in orthographic analysis skills (breaking the written word down into chunks that can be articulated).
Test 10 and 11: Verbal and Semantic Fluency. It is known that dyslexic people often have considerable strengths which may offset their weaknesses. In general these strengths may lie in the areas of creativity and non-verbal reasoning, but the strengths vary from individual to individual and are not easily tapped in a short test. Recent work by Frith and her colleagues (see Chapter 4 - Test Origins). Has suggested that a profile of good semantic fluency ("how many animals can you say in a minute?") together with poor verbal fluency ("how many words beginning with S can you say in a minute?") might be characteristic of dyslexia.
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