Perceptual Illusions: What They Are, Causes, Types And Examples

By observing things around us, we tend to integrate different parts of visual stimuli and organize them into meaningful ways. In general, we carry out this perceptual elaboration of stimuli completely unconsciously, so it seems to us that we grasp things in this way simply because “they are like that.”

This impression of adherence of the percept to objective reality is normally quite correct, but sometimes perception misleads us as illusory perceptual configurations are created. So what are perceptual illusions?

Perceptual illusions, the intriguing phenomena that challenge our sensory perception, have fascinated psychologists and neuroscientists for centuries. These illusions deceive our senses, distorting our perception of reality and revealing the intricate workings of the human mind. In this exploration, we delve into what perceptual illusions are, their underlying causes, various types, and provide illustrative examples to elucidate their captivating nature.

What are perceptual illusions?

Perceptual illusions refer to discrepancies between the objective reality of a stimulus and our subjective perception of it. These illusions occur when our sensory systems misinterpret sensory information, leading to perceptual distortions or misjudgments of size, shape, color, motion, or depth.

Perceptual illusions represent, unlike perceptual constancy, an inaccurate perception of real objects Illusion is, therefore, a perceptual alteration by which perception that does not conform to the characteristics of the stimulus causes a discrepancy between the physical world and the perceived world

It should be said that perceptual illusions They are not only optical illusions, since the latter is based on the introduction of visual tricks that work with human perception; while perceptual illusions are rather a cognitive phenomenon that has as its protagonist the brain processing of sensory information.

Causes of perceptual illusions

The phenomena of perceptual illusions are unequivocal examples of a general truth: perception is organized and cannot be considered simply “given” by the impression of external events. In this way, perceptual illusions are produced by a series of influences:

  • Biological influences: our nature of attention is selective and we also see images as perceptual sets (we fill in the spaces of the image to complete it).
  • Psychological influences: Perceptual illusions are a product of the emotional context and the schemes learned throughout our lives.
  • Sociocultural influences: are those that integrate cultural assumptions and expectations, as well as the effects of the physical context.
  • Sensory Processing: Perceptual illusions arise from the inherent limitations and biases of our sensory systems, including visual, auditory, tactile, olfactory, and gustatory perception. These sensory systems process incoming stimuli and construct our perceptual experience of the world.
  • Cognitive Factors: Cognitive processes, such as attention, memory, expectation, and context, influence our perception of stimuli and can contribute to the occurrence of perceptual illusions. Our prior experiences, beliefs, and cultural background also shape our perceptual interpretations.
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Types of perceptual illusions and examples

  1. Visual Illusions: Visual illusions distort our perception of shapes, sizes, colors, and spatial relationships. Examples include the Müller-Lyer illusion, where lines of equal length appear unequal due to arrowhead-shaped inducers, and the Ponzo illusion, where identical objects appear larger when placed in a converging perspective.
  2. Auditory Illusions: Auditory illusions involve misperceptions of sound, pitch, rhythm, or spatial location. Examples include the Shepard tone illusion, an auditory illusion that creates the perception of an endlessly rising or falling pitch, and the Deutsch tritone paradox, where a series of tones creates the illusion of a continuously ascending or descending pitch.
  3. Tactile Illusions: Tactile illusions distort our perception of touch, pressure, texture, or temperature. Examples include the rubber hand illusion, where synchronous stroking of a rubber hand and a participant’s hidden hand creates the illusion of feeling touch on the rubber hand, and the thermal grill illusion, where alternating warm and cold stimuli produce the sensation of intense heat.
  4. Gustatory and Olfactory Illusions: Gustatory illusions involve misperceptions of taste, flavor, or texture, while olfactory illusions distort our perception of smell. Examples include the thermal taste illusion, where temperature influences perceived taste intensity, and the odor-induced taste enhancement illusion, where odors enhance the perception of taste.

To better understand what perceptual illusions are, it will help you read the following examples on the subject:

1. Ponzo Illusion

Depth perception It can be altered by drawing two divergent straight lines on the sheet. If equal elements are added to the drawing, but appropriately distanced, the objects that are at the convergence of the lines appear further away and therefore higher than those that are where the lines diverge more.

2. The illusion of e Kanizsa

Three colored discs placed on the same plane and from which a small portion has been cut out give the illusion that a white triangle is also drawn on the sheet. There is actually no triangle, as is the case when rearranging floppy disks: our mind completes the picture with just the details.

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3. The Necker cube

What is the front face of the cube? And the back part? The brain cannot decide why has no reference points to determine which part of the cube is closer and which is farther away.

4. Illusions related to color

In Rubin’s Cup Both the object (the cup) and two human profiles can be distinguished depending on whether more attention is paid to the white of the cup or the black of the background.

Another deception in color perception is that which occurs when a homogeneous strip of color is superimposed on a blurred background: the end of the strip that is in the darkest part of the background will appear lighter and vice versa.

5. The impossible figures

There are objects that can only live on paper, but they are totally unrealizable. An example is the endless staircase, in which you can go down or up to infinity because the first and last steps coincide. Endless stairs and other impossible objects are also frequently found in many works made by Maurits Cornelis Escher.

6. Ambiguous images

Young or old? In “My Wife and My Mother-in-Law”, a caricature made by the English artist WE Hill in 1915, you can see both a young woman filmed in three quarters and the profile of a pensive old woman.

Differences between perceptual illusions and hallucinations

Perceptual illusions and hallucinations are phenomena in which an erroneous perception is made. However, unlike the perceptual illusion, which misinterprets a truly existing stimulus, hallucination encounters an external stimulus that does not exist absolutely.

Some examples of hallucinations are: when a person hears a voice without there being a sound or, on the other hand, sees a person and object where there is really nothing or no one. Click on our title Types of hallucinations: causes and examples, if you want to know more about this topic.

Examples of perceptual illusions

Other examples of perceptual illusions that commonly occur are:

The Ames Room

In the Ames Room illusion, a specially constructed room creates the illusion of depth and size distortion, making one person appear much larger or smaller than another when viewed through a peephole.

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The Café Wall Illusion

In the Café Wall illusion, alternating rows of black and white tiles create the illusion of a distorted grid pattern, with horizontal lines appearing to tilt despite being parallel.

The Ebbinghaus Illusion

In the Ebbinghaus illusion, a central circle surrounded by smaller circles appears larger or smaller depending on the size of the surrounding circles, despite being the same size.

The illusion of the moon

The moon appears smaller when it is at its zenith than when it is at the horizon. The explanation of this phenomenon is that The magnitude of an object is determined by comparing it with the environment.

In this way, when we see the moon on the horizon we compare it with elements of the landscape while when it is at the zenith there are no reference points and for this reason it appears smaller to us.

The contrast between black and white

Another situation of perceptual illusion can be easily verified by looking at certain floors with black and white marbles that represent a series of cubes seen of disequilibrium. At times it seems to us that the white faces are “closer” to us, as if they stood out like an extended peak.

However, if we continue to observe, at some point the arrangement is reversed: the white parts move away from us as if they were cavities and the dark parts appear to stand out.

If you liked this article about perceptual illusions, we recommend you read our article Cognitive distortions: what they are, examples, types and exercises, which talks about erroneous interpretations about reality, which prevent us from experiencing the situations that occur to us objectively.

Perceptual illusions offer a fascinating glimpse into the intricate workings of the human mind and sensory systems. By exploring their nature, causes, types, and examples, we gain a deeper appreciation for the complexities of perception and the ways in which our brains construct our perceptual reality.

This article is merely informative, at PsychologyFor we do not have the power to make a diagnosis or recommend a treatment. We invite you to go to a psychologist to treat your particular case.

If you want to read more articles similar to Perceptual illusions: what they are, causes, types and examples we recommend that you enter our Cognitive Psychology category.

Bibliography

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  • Canestrari, R., Godino, A. (2002). Introduction to general psychology/em. Milan: Mondadori.