Temporal order judgment in dyslexia--task difficulty or temporal processing deficiency?

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.