Delusional Perceptions

Jaspers delineated the concept of delusional percept, and Gruhle (1915) used this description to cover almost all delusions — he minimized the importance of delusional intuition Opens in new window.

Schneider (1949) considered the essence of delusional perception to be the abnormal significance attached to a real percept without any cause that is understandable in rational or emotional terms; it is self-referent, momentous, urgent, of overwhelming personal significance and, of course, false.

It is often difficult to decide whether a delusion is truly a delusional percept or is being used to explain the significance of certain objects of perception within a delusional system.

When asked for her evidence, she explained that she had little brown spots Opens in new window on her arms and therefore knew that she was being injected.

The interviewer looked at the spots on her arms, rolled up his sleeve and showed her spots identical in appearance on his own arm. He said that they had been on his arm as long as he could remember and were called freckles Opens in new window.

She agreed that both sets of spots looked similar and accepted his explanation of his own spots, but she still insisted her freckles proved that she was being injected in her sleep. This was a delusional percept.

Another example of what was probably a delusional percept caused considerable problems in surgical management, ultimately resulting in the death of the patient (Porter and Williams, 1997). A 65-year-old woman had flooded her house by leaving all the taps on.

“On admission she was unkempt, with unwashed hair, wearing a dirty dress and vest. She was bringing up bile stained vomit and was reluctant to be interviewed.

She expressed delusional beliefs that her stomach had been blown up with ether over several weeks and that it was liable to burst as a result of a citizens band radio which was located in her stomach.

She believed that the IRA had been after her for years and experienced auditory hallucinations Opens in new window of voices which she identified as coming from the CB receiver.

One ‘voice’ told her not to let anyone examine her. There was no evidence of an acute confusional state and the diagnosis was consistent with a long-term paranoid psychosis Opens in new window.

“On physical examination her abdomen was soft but distended with a hard, craggy, immobile, central mass. The liver and spleen were of normal size and the kidneys were not palpable. Bowel sounds were loud. A diagnosis of possible intra abdominal malignancy was made.

She refused any investigation or treatment. She developed acute renal failure and ultimately died; ascetic fluid revealed adenocarcinomatous cells probably of ovarian origin.

Another patient, who had other delusional symptoms, believed that many of the patients in the hospital were well-known citizens cunningly disguised with wigs, make-up and false beards.

She recognized that they did not look like the people whom she presumed them to be but considered this to be part of a gigantic hoax, in which she was herself involved, to ‘help people spiritually’.

Although her percepts were normal and her interpretations delusional, this was not considered to be a delusional percept but a misinterpretation. All the circumstances in her life were explained in terms of an immensely complicated delusional system, and these perceptions had no immediate personal significance beyond the significance that she found in all the objects and events around her.

In a delusional percept, there is a direct experience of meaning for this particular normal percept; it is not simply an interpretation of this percept to fit in with other established delusional beliefs.

Delusional perception is, therefore, a direct experience of meaning that the patient did not have previously. Objects or persons take on new personal significance that is delusional in nature, even though the perception itself remains unchanged.

This is different from a delusional misinterpretation, in which the delusional system affects all aspects of the patient’s life, and so every event or perception is interpreted as being involved with that delusion. A patient sees that a doorknob is missing; this is not the precipitant of immediate new personal significance of a delusional nature, rather, it further confirms the belief he already held that people are trying to trap him and subject him to vivisection.