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what did szmalec et al (2011) do
ran a 3 part experiment looking at the hebb learning ability (a task relying on on serial order learning) of people with and without dyslexia and across different modalities (Verbal-visual, Verbal-auditory and Auditorily-visuospatial).
what did szmalec et al find?
They observed that individuals with dyslexia, when compared to typical adults, showed smaller improvements in recall of the Hebb sequences across all modalities, relative to the filler trials. However, performance on the nonrepeating filler trials was comparable for dyslexic and typical groups. As a result this study suggested that it was sequential learning that was impaired in dyslexia and not STM, as has been previously suggested. Furthermore, 87% of the typical adults and 81% of the dyslexic participants reported awareness of the Hebb repetitions, suggesting that sequence learning was impaired in dyslexia despite participants having a certain degree of explicit knowledge of their sequential learning processes.
what did Bogaerts (2015) do?
In addition to this, further support for this theory came from a study conducted by Bogaerts et al. (2015), looking at the acquisition and consolidation of Hebb effect in Dutch-speaking adults with dyslexia. In this study a Sequence of 9 CVs were presented visually for immediate serial recall.
What did bogaerts (2015) find?
Overall, the study found that adults with dyslexia showed a significantly smaller Hebb repetition effect than typical peers and required more repetitions of the Hebb sequence to reach the training criterion, suggesting that sequential learning was shown to be weaker and slower in dyslexia. The study also found that dyslexic and control participants showed comparable retention of the long-term serial-order representations in memory over a period of 1 month, and therefore people with dyslexia are fundamentally impaired in the acquisition of serial-order information. So, although there is weaker lexicalization of newly acquired word-forms in the dyslexic group, what is learned is consolidated over time.
What did Staels and Van den Broeck (2015) find?
For example, Staels and Van den Broeck (2015) failed to replicate the significantly reduced Hebb effect in adolescents and children with dyslexia, regardless of whether the same data-analytical procedure as Szmalec et al. was used or whether some methodological improvements were applied (e.g., using a more sensitive index of Hebb learning, and equating groups on filler performance with state trace analysis).
What did Henderson & Warmington (2017) do?
ran a study investigating the learning and consolidation of sequential knowledge in 30 adults with dyslexia and 29 typical adults matched on age and nonverbal ability. The study used two tasks, a hebb learning task and a serial reaction time (SRT) task, that had both been previously reported to be sensitive to a sequence learning deficit.
What did henderson and warmington find (2017) find?
In the SRT task, they found that both the dyslexic and non dyslexic participants showed evidence of sequential learning and consolidation (i.e., faster and more accurate responses to sequenced spatial locations than randomly ordered spatial locations). Whilst in the hebb learning task, they found that typical adults showed evidence of sequential learning (i.e., more accurate serial recall of repetitive sequences of nonwords versus randomly ordered sequences) and that adults with dyslexia showed initial advantages for repetitive versus randomly ordered sequences in the first half of training trials. However, in the second half of training,this effect disappeared. Although it was found that the hebb repetition effect was positively correlated with spelling in the dyslexia group there was no correlation between sequential learning on the two tasks, placing doubt over whether sequential learning in different modalities represents a single capacity. As a result they concluded that sequential learning difficulties in adults with dyslexia are not present everywhere, and when they are present, it may be a consequence of task demands rather than sequence learning per se.
Henderson and Warmington (2017) conclude
As a result they concluded that sequential learning difficulties in adults with dyslexia are not present everywhere, and when they are present, it may be a consequence of task demands rather than sequence learning per se.
