The authors look at perceptual patterns for a seventh-grade French dyslexic, MT, who has no phonological deficit. In particular, they look at trigram identification across a range of retinal locations (centered from -7 to 7), for MT versus seven age-matched controls. The authors fit curves to the trigram data, and did not find any difference between MT and the controls.
However, the SERIOL model makes quite specific predictions of how perceptual patterns should differ between dyslexics and controls, which the authors did not evaluate. The model predicts that a letter's position within the string should have a much stronger influence in the LVF than the RVF. This is due to the proposal of learned left-to-right inhibition in the LVF/RH. For younger readers, this effect should be strongest near fixation, where perceptual learning is the strongest. For example, accuracy for a letter at retinal location -2 should be much better when it is the 1st letter in the string than when it is the 3rd letter. In contrast, accuracy for a letter at retinal location 2 should be minimally affected by its position within the string. This asymmetry should be a signature of normal visual/orthographic processing, and it should be absent for dyslexics, under the assumption that they are not performing normal visual processing.
Indeed, inspection of the data in Figure 6, shown above, supports this prediction. In this figure, a filled circle represents the 1st letter in the LVF and the 3rd letter in the RVF. Conversely, an open circle represents the 3rd letter in the LVF and 1st letter in the RVF. For controls for eccentricities of 1 to 3 letter widths, it is evident that string position had a strong effect in the LVF, but not the RVF, while the pattern was symmetric for MT. Examination of the individual data shows that the asymmetric pattern held at the individual level.
Of course, this is a very small sample size. I would suggest that it is important to try this experiment on a large group of school-age controls and dyslexics to see how diagnostic this asymmetric vs. symmetric pattern truly is. If it is highly diagnostic, this would be quite informative as to the nature of core deficits in developmental dyslexia.