Hallucinations vs Illusions: Difference and Comparison

The object causing the hallucination does not exist in objective reality, while the object causing an illusion does have a human existence. The individual’s cognitive, auditory, visual, and tactile senses misinterpret the real object’s external stimuli- effectively producing illusions.

People commonly experience both these episodes, although hallucinations are classified as symptoms of psychological ailments.

Key Takeaways

1. Hallucinations are false perceptions without any external stimulus, involving any of the five senses.
2. Illusions arise from misinterpreting real sensory input, leading to distorted or altered perceptions of reality.
3. Hallucinations and illusions can result from various factors, including mental disorders, substance use, or neurological conditions.

Hallucinations vs Illusions

The difference between hallucinations and illusions is that while hallucinations occur in the absence of any real external stimuli, illusions are episodes produced due to a mismatch between the external stimuli and the perception by the individual.

Comparison Table

Parameters of Comparison	Hallucinations	Illusions
Definition	They are states produced by false perceptions of internal stimuli.	They are states produced by misinterpretation of real stimuli.
Stimuli	The stimuli that initiate the episode are not real.	The stimuli that initiate the episode are real.
The Universality of the Experience	Hallucinations are extremely personal and cannot be universally uniform. They cannot be shared experiences.	Illusions can be experienced simultaneously and uniformly by a group of people. They can be engineered as shared experiences.
Connotation of the Episode	Hallucinations are considered to be abnormal and associated with a pathological state of the mind.	Illusions are considered fairly common to be experienced by a healthy, normal individual.
Use for Mental Stimulation	Hallucinations are not used for active mental stimulations.	Illusions are commonly used for mental stimulation through works of art and architecture.

What are Hallucinations?

Hallucinations are caused by the perception of objects that do not exist. Originating from the Greek word ‘hallucinat’, they are defined as false perceptions caused by malfunctioning the central nervous system.

They may present as symptoms of psychosis in an individual. Hallucinations are associated with diseases like Schizophrenia, Parkinson’s, and Post-Traumatic Stress Disorder.

Such psycho-sensory disruptions can be both auditory as well as visual episodes. These experiences may be defined as ‘voices’ by the individual experiencing them.

Olfactory and somatic hallucinations are also common. The former refers to smelling something not present in the corporal world, and the latter refers to a feeling that one’s body is being injured.

An individual may feel his skin crawling as part of a hallucinatory episode or see patterns or objects where there are none. Three essential grounds must be satisfied to classify an episode as a hallucination.

These conditions are: the object of the episode has to be unreal; the episode has to produce a sensory experience; and finally, the individual experiencing the hallucination has to be convinced of its contextual reality.

What are Illusions?

Illusions are misinterpreted perceptions. The stimuli or objects of such perceptions are real, but their interpretation is flawed.

Illusions are produced when our sensory organs misinterpret external stimuli. These episodes may be classified into visual, olfactory, cognitive, optical, and geometric illusions.

Psychologists have studied illusions to understand the operation of the human perceptive system. The perception of certain events in an erroneous manner can lead to the development of illusions.

Overstimulation of sensory organs may also result in illusions. When a discrepancy occurs between the varieties of information relayed through our multiple sensory organs, illusionary episodes are commonly experienced.

Here the facts of corporeality are being misinterpreted by our cognitive system.

For instance, a child experiences an illusion when she interprets the shadows in the dark as monsters or animals. This is an apt example of an illusion caused by the improper interpretation of visual cues.

Main Differences Between Hallucinations and Illusions

1. The main difference between hallucinations and illusions is in terms of perception. False perceptions with no corresponding external stimuli result in hallucinations. Illusions are produced due to an erroneous perception of very real, existent stimuli. They are called ‘sensorial errors.’
2. The second difference is the corporeal existence of the stimuli that produce each episode. While hallucinations result from non-existent stimuli, illusions are episodes created by real stimuli. Moreover, the perceived stimuli are internal in the former, while the latter is always external.
3. Illusions can be shared experiences, while hallucinations are more commonly intimate and personal. For instance, optical illusions can be simultaneously experienced by all audience members at a magic show. As internal stimuli produce hallucinations, they tend to be specific to the individual and his prior experiences and mindset.
4. The experience of illusions is considered quite normal in individuals. However, hallucinations can be symptomatic expressions of psychological ailments like Schizophrenia and Dementia.
5. Optical illusions are easier to be researched and theorize effectively. Hallucinations are deeply personal experiences. As a result, the possibility of researching these experiences is minimal and extremely strenuous.
6. Illusions are considered to be ways of stimulating the mind. Optical illusions are reflected through works of art to encapsulate and interest the audience. Magicians also use optical illusions to allure the interest of their audience members. However, hallucinations are not used for positive mental stimulations. If not induced medically or by a substance, their occurrence is linked to psychiatric pathology. They are produced by internal stimuli that are so personal and specific to individuals- unlike illusions- that it is impossible to induce them in large populations.

References

1. https://ajp.psychiatryonline.org/doi/pdf/10.1176/ajp.58.3.443
2. https://www.ncbi.nlm.nih.gov/pubmed/10420378