no you dont learn to dissociate (separate the core from the alters) if you have DID its already been done, otherwise there would not be alters.

do you mean how do you tell the difference between the core and the alters?

no its not something you learn.

its just one of those things each persons system of host (core) and alters know about each other. by that I mean alters are created for a reason/job/purpose. they know what their purpose/job and place is within the system, and they know they are there to protect the host (core) and do what the host (core) cannot.

the answer to the testing question - if the host (core) cannot be tested then you don't get diagnosed with DID, you dont get diagnosed with having alters and you dont get an accurate GAF / IQ scoring.

short versions - the diagnostics for DID state

the person must have 2 or more alters that take control
the person must have a type of forgetfulness that goes beyond normal forgetfulness
the symptoms / problems can not be because of alcohol, drugs or other health problems like seizures.

the testing treatment provider must be able to talk to the host(core) and at least two alters. if this doesnt happen the treatment provider cannot diagnose someone with DID.

the mental maturity (GAF/IQ) is part of the diagnosing process of DID. so if you have been diagnosed with DID to find out what your host(core) mental maturity is, just look on the diagnostic report under GAF / IQ.

if you have not been diagnosed with DID you can get the testing through your treatment providers.