Three descriptive questions
Was there an external stimulus? Was it experienced differently from its usual qualities? Was an additional sensory experience reported? These questions help distinguish a distortion of a real stimulus, an illusion and a hallucination. Begin with a concrete account rather than asking the person to choose a label.
A sensory distortion changes qualities such as intensity, size or shape. An illusion involves misperception of a stimulus that is present. A hallucination is a perception-like experience without a corresponding stimulus adequate to explain it. These descriptions are starting points for assessment rather than diagnoses.
Describe the dimensions of the experience
Record the sensory modality, onset, frequency, setting, clarity and effect on the person. Ask whether the experience occurs while fully awake or around sleep, and whether it changes with illness or substance exposure. Establish the person’s interpretation, degree of uncertainty and distress.
For voices, distinguish the experience itself from the explanation attached to it. Where it seems located and whether it is recognized as unusual are useful details, but neither alone settles classification. The term pseudo-hallucination has been used inconsistently; describing the dimensions is often clearer.
Keep context in the interpretation
Perceptual experiences can occur in several psychiatric and medical contexts and sometimes outside a mental disorder. Cultural meaning, sensory factors and the surrounding clinical picture matter. An unusual experience should not be translated automatically into a primary psychotic diagnosis.
For learning, compare two accounts with the same sensory modality but different triggers and meanings. Ask what further history would distinguish them. The goal is a precise description that remains open to more than one explanation.
For your next supervision discussion
Compare seeing a real object differently with reporting an additional perception-like experience. Which questions about stimulus, setting and the person’s interpretation would make the distinction clearer?
References · 2
Page numbers distinguish PDF position from the numbering visible within the supplied document.
- Fish’s Clinical Psychopathology: Signs and Symptoms in PsychiatryPatricia Casey and Brendan Kelly · 5th edition, 2024.Disorders of perception: sensory distortions and sensory deceptions. PDF pages 33, 34, 35, 36; printed pages: 24–27.Supports: Distortions, illusions, hallucinations and terminology limitations.
- Clinical descriptions and diagnostic requirements for ICD-11 mental, behavioural and neurodevelopmental disordersWorld Health Organization · 2024.Schizophrenia and other primary psychotic disorders: cultural considerations. PDF pages 179, 180; printed pages: 161–162.Supports: Cultural and differential context.