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Most research on learning disabilities (LD) is conducted on relatively small samples, with the majority of work being focused on school aged populations, and in particular those in the elementary school age/grade range. Thus, there has been little research available specifically focused on an adult population (Gottardo, Siegel, & Stanovich, 1997) as illustrated by an attempt at a meta-analytic review of research on remedial programs for adults that was unsuccessful due to the small number of studies, differing intervention strategies, different samples used, and methodological concerns (Torgerson, Porthouse, & Brooks, 2003).

In addition, it has been suggested that those working with the adult literacy community and those working with the adult learning disability community have typically had different pedagogical approaches, assumptions, target populations and interventions (Fowler, & Scarborough, 1993). However, accumulated evidence from research on children and adults suggests that this dichotomy may not be a useful approach. In particular, it has been repeatedly demonstrated within a school aged population that those meeting traditional definitions for reading disabilities do not differ in meaningful ways from those simply classified as poor readers. In both cases, primary deficits in cognitive-linguistic domains, such as phonological processing, have been identified (Felton, & Wood, 1992; Shaywitz, Fletcher, Holahan, & Shaywitz, 1992; Siegel, 1989; Vellutino, Scanlon, & Lyon, 2000). Bone, Cirino, Morris and Morris (2002) replicated this finding with an adult sample. Similarly, there does not appear to be any significant difference between the two groups, reading disabled and poor readers, with respect to response to phonologically based treatments (Kruidenier, 2002; Vellutino, et al., 2000). In essence, there appears to be a point of confluence where poor reading due to poverty of experience or specific reading disability leads to similar problems at the cognitive-linguistic level. However, to date there have been no large scale investigations designed to evaluate for meaningful differences between those with low literacy skills and those with a learning disability, particularly a reading disability, in an adult sample with particular reference to outcomes. It may be that if the same explanatory variables are linked to both LD and low literacy that these two solitudes may be better considered as a single issue or at least be recognized as being so closely related that differentiating between them given the current state of intervention strategies is unnecessary and overly burdensome to both individuals and the larger adult education system as a whole. This requires acknowledging that poor reading skills may arise for a myriad of reasons, not just the presence of a LD and that interventions can be successful regardless of the reason for poorly developed reading skills.

A number of variables have been demonstrated to have a robust influence on Prose literacy scores including such things as: 1) gender, where it has been consistently shown that females demonstrate higher prose skills compared to males (Desjardins, 2005a), 2) age cohort, where younger cohorts tend to score higher than older cohorts (Desjardins, 2005a), 3) education level, where higher levels of education result in better scores (Desjardins, 2005b), 4) income, where higher income is associated with better scores (Desjardins, Werquin, & Dong, 2005), 5) parent level of education, where higher levels of parental education are linked to higher scores and 6) reading practices, where more reading is connected to higher scores (Willms, 2005).

In addition to the influence of LD on prose scores, it is also important to understand which variables are most strongly associated with LD in an adult population. As noted, there are relatively few studies focusing on adults compared to what is available in reference to children. As a result there are a number of unanswered questions and/or contentious issues relating to the prevalence, distribution and influencing factors associated with the reported presence of a learning disability, in large part due to the lack of evidence specific to the adult population. Four key variables can be identified in the research literature that have been relatively widely studied and yet continue to be debated due to conflicting or limited evidence. These are: gender, age, attained education level, and income/employment status as adults. The relationship of these variables to LD is either somewhat contentious or has been generally accepted as a matter of fact based upon the results of relatively few studies. As such, these four variables were selected for inclusion in the present study in order to clarify their relationship to self-reported LD in an adult population. The following is a brief review of each of these variables and a sampling of the related research findings:

Gender: For many years the higher prevalence of LD in males was considered to be an established fact. However, more recently there has been increasing debate regarding this issue. For instance, Siegel and Smythe (2005) took the perspective that gender differences were an artifact of the definitional criteria used in diagnosing LD and they supported this perspective by citing a large scale longitudinal study of school aged individuals who were followed from kindergarten to grade 5. Their results demonstrated that although some gender differences were observable in kindergarten and grade 1, after that point there were essentially no measurable differences between genders. In contrast, Liederman, Kantrowitz, and Flannery (2005), argue that gender differences are present. They use a review of high quality studies and an associated critical analysis of these to support the contention that gender differences are not the product of definitional criteria, ascertainment bias, statistical artifacts and related concerns, but rather reflect actual differences due to gender.

Age: Age, in and of itself, should not be related to the presence of a learning disability given that learning disabilities by definition are neurologically based and lifelong (Learning Disability Association of Canada, 2001). However, prevalence rates should rise based upon age cohort since Learning Disability as a formal diagnostic category was not established until the early 1960's. As such, the number of those over the age of 45 who report a learning disability could be expected to be significantly lower than those under the age of 45. According to LDAC "The age of 44 was identified… since 'learning disability' was first applied in the early 1960's, and those identified by diagnosticians in the late 1960's and early 1970's are now in this age bracket." Interestingly, Mellard and Patterson (2008) in a study using 311 Adult Development Education (ADE) participants in the Midwestern states to identify differences between those reporting a LD with those who did not, found that those reporting LD were more likely to be in the 46-55 year old age bracket.

Education: Given the educational struggles typically faced by those with LD it would be expected that academic outcomes would be lower as compared to peers. In particular it would be anticipated that fewer individuals with LD would graduate from high school and fewer still would go on to post-secondary education. Levine and Nourse (1998) in a review of the literature related to LD, gender, education and employment reported a number of methodologically sound studies that demonstrated that LD students were less likely than their peers to pursue post-secondary education. However, Mellard and Patterson (2008) found in a sample of adult education learners that those with LD were more likely to complete high school compared to those without LD. Though this tends to contradict most other studies it was suggested that those with a formal diagnosis may have received greater support from the school system that allowed them to reach graduation.

Income and Employment Status: As with educational outcomes it would be anticipated that those with LD would be more likely to be unemployed and if working would be in either relatively low paying/skill jobs and/or perhaps face wage discrimination. Again Levine and Norse's (1998) review of the literature suggest that unemployment and low paying/skill jobs were present to a higher degree in those with LD, though significant methodological issues were identified in the research reviewed. Mellard and Patterson (2008) noted that participants in ADE programs with and without LD tended to demonstrate similar employment rates and similar status jobs. This would suggest that educational attainment and basic literacy skills may be the key factor in these issues as opposed to LD status per se. In addition, Dickinson and Verbeek (2002) analyzed a data set to determine if there was a wage differential between college graduates with and without a LD. Results showed a wage differential was present that did not appear to be related to overt discrimination, but rather the authors attributed the difference to productivity characteristics of the individuals.

Additional variables, variables of interest, were also identified since they have been associated with educational outcomes generally or they have been linked to LD but have been considerably less studied in reference to LD. These variables of interest include: 1) parents' education level - separated for father and mother, 2) self-reported co-occurring disabilities - hearing, speech, vision, and other lasting more than six months, 3) remedial reading activities while in school, and 4) reading practices at home. The rationale for identifying each of these as variables of interest is as follows:

Parents' level of education: First, it has been clearly established that genetics play a role in the development of a LD (Shaywitz, & Shaywitz, undated). As such, there may be a relationship between the level of education attained by parents and that attained by offspring. In addition, if clear gender differences in prevalence rates do exist in favour of males having higher rates of LD it would be expected that father's level of education would be a stronger predictor of LD status than mother's level of educational attainment. In addition, parental level of education has been shown to be a significant factor related to literacy levels, such that those with more highly educated parents tend to have higher literary scores (Kaplan, & Venezky, 1993; Willms, 2005). Interestingly, Mellard and Patterson (2008) found no difference between mothers' high school or post-secondary completion between those reporting, and those not reporting a LD.

Co-occurring disabilities: A number of research studies have demonstrated that those with learning disabilities are more likely compared to those in the general population to have or to have had other disabilities, with speech and hearing disabilities being commonly identified. This is illustrated by Vogel and Holt (2003) who reviewed results from the first IALS (1994) survey and noted that within Canada 18% of those with a LD compared to 8.37% without reported a hearing disability and 11% versus 2.96% reported a speech disability. Similarly, Shapiro (undated) indicated that the presence of a hearing or speech impairment was a risk factor associated with reading disability. The co-occurrence of visual disabilities is less commonly reported, though Stein (2001) has theorized that a visual issue may underlay reading impairment, Solan, Shelly-Tremblay, Hnason and Larson (2007) concluded given the results of their study "… that a common linkage exists between reading comprehension, visual attention, and magnocellular processing." (p. 270), and a significantly higher rate of visual difficulties was noted in one study of ADE learners (Mellard, & Patterson, 2008). The "other disabilities" category was included given the range of disabilities that have been linked to LD and the observation by Vogel and Holt (2003) that 26% of LD compared to 10.98% of non-LD respondents endorsed this item.

Remedial reading: Reading disabilities are the most common LD accounting for 80% of those reported (Shaywitz, & Shaywitz, undated). In addition, those with LD would tend to experience greater difficulty with academic material compared to the general population. As such, it was expected that those with a LD would be more likely to have been enrolled in remedial reading programs while in school. Such findings were noted by Mellard and Patterson (2008) where 75% of those with LD reported participating in remedial or special programs while in school. This translated into those with a LD being nine times more likely to have undergone such programs. However, evidence of this phenomenon is limited.

Reading practices at home: These variables have been demonstrated to be significant factors in literacy skill attainment and retention in the adult population (Willms, 2005) and were included to evaluate their relationship to LD.

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