In addition to the information on interpreting the results given in Chapter 4, there are some additional factors to consider when screening individuals who have low levels of basic skills. In such cases the automatic interpretation given by LADS Plus should be regarded as a good general indicator but the profile may need closer scrutiny. Administrators working with adults who have low levels of basic skills should be particularly aware that in these circumstances there a greater risk of ‘false positives’ i.e. individuals who show positive on screening but who do not, in fact, have dyslexia. This is especially so in groups of prisoners and young offenders, who typically have disadvantaged backgrounds and disrupted schooling, often resulting in low literacy levels. The issue of the incidence of dyslexia in prisoners and young offenders remains controversial. Many researchers have maintained that there is evidence for a higher level of dyslexia in those convicted of criminal offences than there is in the general population. For example, in the Dyspel project carried out in London in the mid-1990s, 52% of offenders screened showed strong indicators of dyslexia (e.g. Morgan, 1997). Kirk and Reid (1999) reported similar figures in a screening study of young offenders in Scotland. The reasons for this are often assumed to lie in the greater vulnerability of young people who have undiagnosed dyslexia resulting in educational failure. Other commentators (e.g. Rice, 2000) have criticised this view, maintaining that the evidence is spurious because the incidence of false positives is rarely taken properly into account. However, regardless of whether the incidence of dyslexia in such groups is greater than elsewhere, the arguments in favour of screening adults with poor literacy skills and who may therefore have dyslexia remains the same. For a general review of the issues surrounding this, see BDA (2005) and Reid and Kirk (2001).
The results from the non-verbal reasoning test are unlikely to be affected social and educational background factors. This one reason why this is such a useful test. Often it will reveal that an individual who may have been assumed not to be particularly bright (because of poor oral vocabulary) is much more capable than was previously imaged. It would, however, be very common for this type of client to obtain a high score (red bar) on the Word Recognition test, indicating a major area of difficulty. This is because although the words used in this test are fairly common, lack of reading experience is likely to mean they have difficulty in making decisions about what might be real words as opposed to nonwords, especially under conditions of time pressure.
The areas that yield very useful information in terms of dyslexia identification are the Word Construction and Memory tests. If these are giving positive indications (red bars/high scores) then the overall probability of dyslexia is likely to be high.