Thursday, July 15, 2010

Research byte 7-15-10: Temporal processing dyslexia deficity might be explained by task difficulty instead?

Interesting article that raises question with the temporal processing hypothesis of dyslexia being completely able to account for severe reading difficulties.  The authors re-analyzed data from a previous study and demonstrated that the same data would support the hypothesis that the slower temporal processing of individuals with dyslexia may be a function of the increasing task difficulty of the tasks used.....that is, slower temporal processing occurs as the tasks being performed become more difficult. 

A good reminder that now all is known about human behavior and that science is a cumulative endeavor.  Favored/popular causative hypotheses (e.g., temporal processing as a core deficit of dyslexia) need to be viewed with a healthy degree of positive skepticism.

Skottun, B. C., & Skoyles, J. R. (2010). Temporal order judgment in dyslexia-Task difficulty or temporal processing deficiency? Neuropsychologia, 48(7), 2226-2229.

Dyslexia has been widely held to be associated with deficient temporal processing. It is, however, not established that the slower visual processing of dyslexic readers is not a secondary effect of task difficulty. To illustrate this we re-analyze data from Liddle et al. (2009) who studied temporal order judgment in dyslexia and plotted the results as d' as a function of Stimulus Onset Asynchrony (SOA). These data make it possible to compare the results of dyslexic readers and controls both in terms of d' which is related closely to task difficulty and in terms of time (i.e. SOA). It is found that the difference between the groups is about equally well accounted for in terms of d' as in terms of temporal factors. This suggests that the results of Liddle et al. (2009) may be equally well accounted for in terms of general task difficulty as temporal factors.

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