Actors role playing DID can be identified from differences in brain activation patterns, compared to people with DID - and brain activation patterns depend on whether an trauma holder alter / EP is in charge or a Apparently Normal Part / host - supporting the Theory of Structural Dissociation of the Personality (TSDP).
Multiple brain scan studies support structural dissociation, brain activation differences between alters, brain activation differences between people with DID and healthy controls or trained actors pretending to have DID.
Regions of the brain activated are those known to be associated with self-referencing and sensorimotor actions, but not the regions linked to imagination
Schlumpf YR, Reinders AATS, Nijenhuis ERS, Luechinger R, van Osch MJP, Jäncke L (2014) Dissociative Part-Dependent Resting-State Activity in Dissociative Identity Disorder: A Controlled fMRI Perfusion Study. PLoS ONE 9(6): e98795.
Background In accordance with the Theory of Structural Dissociation of the Personality (TSDP), studies of dissociative identity disorder (DI
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3791283/