The evidence for "Special Mycenaean" as a distinct dialect has, however, been challenged. Thompson argues that Risch's evidence does not meet the diagnostic criteria to reconstruct two dialects within Mycenaean. In particular, more recent paleographical study, not available to Risch, shows that no individual scribe consistently writes "Special Mycenaean" forms. This inconsistency makes the variation between "Normal Mycenaean" and "Special Mycenaean" unlikely to represent dialectical or sociolectical differences, as these would be expected to concentrate in individual speakers, which is not observed in the Linear B corpus.