Schneider named five features of formal thought disorder:
- Derailment
- Substitution
- Omission
- Fusion
- Driveling.
Derailment
There is a disordered intermixture of constituent parts of one complex thought.
Schneider suggested there were three features of healthy thinking:
Constancy
This is characteristic of a completed thought that does not change in content unless it is superseded by another consciously derived thought.
Organization
The contents of thought are related to each other in consciousness and do not blend with each other but are separated in an organized way.
Continuity:
There is a continuity of the sense continuum, so that even the most heterogeneous subsidiary thoughts, sudden ideas or observations that appear are arranged in order in the whole content of consciousness.
Schneider claimed that individuals with schizophrenia complained of three different disorders of thinking that correspond to these three features of normal or non-disordered thinking.
Transitory thinking
Transitory thinking is characterized by derailments, substitutions, and omissions. An omission is distinguished from desultory thinking because in desultoriness the continuity is loosened but in omission, the intention itself is interrupted and there is a gap. The grammatical and syntactical structures are both disturbed in transitory thinking.
Driveling thinking
With driveling thinking, the patient has a preliminary outline of a complicated thought with all its necessary details but loses the preliminary organization of the thought, so that all the constituent parts get muddled together. A patient with driveling has a critical attitude towards their thoughts, but these are not organized and the inner material relationships between them become obscured and change significance.
Desultory thinking
In desultory thinking, speech is grammatically correct, but sudden ideas force their way in from time to time.