Hallucinations are not the main symptoms of schizophrenia. Rather, hallucinations are accessory symptoms present in some forms of schizophrenia. They are usually acoustic but can be also tactile, olfactory or gustative. Hallucinations are usually followed by delusive ideas.
There are 4 main types of schizophrenia: hebephrenic, simplex, catatonic and paranoid. Symptoms that are present in all types of schizophrenia (main symptoms) are:
1. disorders of associations (disturbed thinking processes);
2. lost emotions (apathy, lost ability for joy or sorrow);
3. ambivalence (the presence of two opposing ideas, attitudes, or emotions at the same time), and
4. Autism (a condition where the contact with reality is lost but the consciousness is still present)
Accessory symptoms present only in some types of schizophrenia include:
1. hallucinations;
2. delusive ideas;
3. catatonic symptoms;
4. poor and bizarre speech etc.
Hallucinations and delusive ideas are typical during paranoid schizophrenia. Most people can’t understand a schizophrenic's delusive thoughts because these people live quite literally in their own world.