Explore multisensory illusions, including the McGurk effect. Discover how sight, sound and timing influence perception, with explanations and source links. How sight, sound, and timing influence one another.
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When viewing the video, you should experience the voice as coming from the puppet, even though the source of the sound is actually the puppeteer.
Although the sound remains the same throughout the video, when watching different lip movements, you should experience an illusory change in the sound.
Moving imageSome people report that they hear the sound of the pylon hitting the ground - a thudding or boinging noise - but not everyone does.
The disk always flashes once. Sometimes it is accompanied by one beep, and then people report one flash. However, when it is accompanied by two beeps some people report experiencing two…
A double portrait with a skull that emerges from an oblique view.
Three convincing corners. One impossible connection.
A flat ceiling opens into a convincing dome, entirely through paint.
A flattened body and leaf-like legs make an insect resemble part of a plant.
Rudolf II appears as a face assembled from fruit, flowers, and vegetables.
Two figures beneath an arch become the eyes of a much larger face.
A familiar cube frame acquires an impossible set of overlaps.
A simple iteration creates a boundary with extraordinary detail.
A beak becomes a pair of ears. Nothing in the drawing changes.
The front of a painting pretends to be its back.
Repeated complex mappings produce intricate connected shapes or dust-like sets.
Perfectly parallel mortar lines seem to slope.
A ceiling seems to open onto the sky, with figures peering down.
The neighbors change the size of the circle you see.
Black dots flicker across a grid of white dots.
One portrait, two women, two very different ages.
Identical curved pieces seem to have different sizes.
Equal diagonals look unequal inside different frames.
The upright line seems longer than its equal horizontal partner.
One gray looks light; the same gray looks dark.
A staircase that climbs forever and gets nowhere.
Three prongs quietly become two supports.
Still gradients seem to drift at the edge of vision.
A hollow face can look like a face turned toward you.
Moving imageDiagonal stripes move sideways but seem to travel upward.
A barber seems to move around your head, with scissors and clippers sounding startlingly close to your ears.
A bowl of vegetables becomes a face when the image is turned upside down.
A fruit basket doubles as a portrait when inverted.
Painted surfaces inside a box become a convincing domestic interior.
Letters and instruments seem to hang in front of the painted surface.
A cut-out painting imitates an easel supporting another painting.
A painted cabinet appears to hold real silverware.
A violin, papers, and painting tools seem attached to the wall.
Painted architecture extends a church ceiling toward an open heaven.
Figures and clouds appear to overflow the ceiling’s golden frame.
A painted dome becomes a swirling ascent into heaven.
A painted table surface seems covered with cards, papers, coins, and tools.
Old papers and everyday objects seem attached to a real rack.
Swans and trees above a lake become elephants in its reflection.
A crouching figure echoes a stone hand holding an egg and flower.
Repeated Venus figures assemble into the hidden face of a bullfighter.
A close view of Gala looking at the sea becomes Lincoln’s portrait from farther away.
Equal fields look different because of a narrow gradient at their boundary.
Color seems to spread into areas that were never filled.
Straight sides and a circle appear distorted over a radiating background.
Overlapping fine patterns produce a larger rippling pattern.
A repeated dot pattern contains a hidden three-dimensional shark.
Concentric circles seem to intertwine.
Saturated colors can appear brighter than equal-luminance gray.
The same central texture appears to have different contrast.
A subdivided distance can look longer than an empty one.
Believable isometric corners combine into an inconsistent structure.
A skew four-sided frame changes its depth logic at the corners.
A six-sided beam loop carries impossible depth around its perimeter.
Eight sides make a deceptively convincing impossible loop.
A triangle of blocks recalls Reutersvärd’s pioneering impossible figure.
A public sculpture appears to form an impossible cuboid.
A real wooden construction looks like an impossible cube from one view.
An arrangement of real nuts and bolts looks impossible from its chosen view.
A close view reveals spirals, branching filaments, and smaller structures.
A variation of complex iteration produces forms reminiscent of ships and towers.
Repeated right-angle turns fold a simple line into a complex shape.
Tangent circles fill gaps with smaller and smaller circles.
You should experience a 'Gestalt switch' - a change - as your experience flips between being of a woman and being of a skull.
Moving imageYou should experience a sense of perceptual confusion as you note the paradoxical nature of the depicted ring.
You should feel as if your fingers are touching two objects, not one.
You should experience a sense of perceptual confusion as you note the paradoxical nature of the building and other features in the lithographic print.
You should have an experience of a third beat that accompanies the sound. Also, as the video proceeds, the apparent beat should change, as the sounds that you receive from left and right…
You should experience the tune to switch between two different tunes, in a similar way that a Gestalt switch happens in some visual experiences.
You should experience a 'Gestalt switch' between seeing the image as a book or cleavage.
You should have the visual experience of a man reaching down to get a book from a librarian. However, although the man reaching down is real, the library and the librarian are just a…
You should experience a 'Gestalt Switch' between seeing the church tower as a building, and seeing it as a chicken face.
You should experience a 'Gestalt switch' between seeing the image as a containing a pattern of squares versus a pattern of circles.
Many people perceive every second line being smooth and curved, and the others being angular, zigzag lines. However, there are no angular, zigzag lines in the image. Hovering your cursor…
Moving imageYou should experience a 'Gestalt Switch' between seeing the figure as an Eskimo or a face.
Moving imageMost observers report that the green square appears to “lag” the red square, i.e. the green square appears slightly to the left of the red square’s horizontal position. However, the green…
You should have the experience of red strawberries in the picture, but the picture doesn't contain any red colour.
You should have the visual experience of giant people seeming to stand on top of buildings. However, although people are real, they are not giants and the buildings they seem to be…
You should experience a sense of perceptual confusion as you note the paradoxical nature of the corners.
The tower on the right seems to lean more, so it is surprising, that these are actually two identical pictures of the tower side by side!
The black and white test figure will have taken on an illusory tinge of colour - the horizontal white stripes appear tinged red, while the vertical stripes appear green.
You should experience a 'Gestalt Switch' between seeing the figure as a young man or old man.
You should experience an image similar to the pink inducing circles in the region of the white inducing patch. It should exhibit inverted colours, appearing yellowish-green.
You should have the visual experience of a man riding a mythical bird. However, although the man is real, the bird is just a cleverly constructed 2D drawing on the pavement.
You should experience a 'Gestalt switch' between seeing the triangle as 'pointing' in each of the three directions corresponding to its angles.
When your eyes are closed and covered again, you should continue to experience the view through the window, or the lamp, or the computer screen, which will likely fade away quickly. This…
You should experience the beat as constantly speeding up. This is only illusory.
You should experience a 'Gestalt switch' between experiencing the triangles as pointing downwards and resting on the dark grey lower plane, or as pointing upwards and resting on a light…
Bright lines will appear to be coming from the centre. If you look at them directly, you will realise that they are not actually there.
In the first sound file, you should experience the pitch as ever increasing. In the second file, you should experience the pitch as ever decreasing. These are illusory experiences, for the…
You should have the visual experience of a man seeming to climb down into a 3D swimming pool. However, although the man is real, the swimming pool is just a cleverly constructed 2D drawing…
When you press your hands to the flat surface you should experience the flat surface as curved for a few seconds.
In the first few seconds you should notice that the dove appears red—a faint version of the red that was in the background of the first image. You are experiencing a positive afterimage…
You should have the visual experience of a woman seeming to stand on top of a crevasse. However, although the woman is real, the crevasse is just a cleverly constructed 2D drawing on the…
Moving imageYou should experience the dots in the test pattern as moving - even though they are stationary.
You should have the visual experience of a person seeming to crouch on a rock on top of a waterfall. However, although the person is real, the waterfall is just a cleverly constructed 2D…
A painted cupola makes an existing vault seem to open upwards.
A room’s walls appear to open through columns into the landscape beyond.
A short colonnade looks like a much longer passage.
A shallow space behind the altar appears to contain a deep, vaulted choir.
Short stage streets appear to run deep into an ancient city.
Scattered yellow marks join into three complete rings from one viewpoint.
A reflection makes visitors lying on the ground seem to climb a house.
Speckled wings repeat the tones and texture of tree bark.
A winter coat makes a white fox difficult to separate from snow.
The same shark presents a dark back from above and a pale belly from below.
Mottled skin and a fringe around the body help a gecko merge with its resting surface.
A cuttlefish can change both its skin pattern and its surface texture.
Translucent tissues reduce the visual barrier between a small frog and its surroundings.
Rounded leaf pairs resemble the pebbles around them.
Leaf-like appendages turn a fish’s silhouette into an apparent tangle of seaweed.
A crab borrows living cover from its habitat instead of relying only on its own colour.
Mottled feathers make the boundary between bird and ground difficult to follow.
Loose fibres soften the recognisable outline of a human body.
Paint changes the contrast and familiar visual pattern of exposed skin.
An irregular surface replaces the crisp edges of the object underneath.
A manufactured observation post is made to look like an ordinary tree.
Bold geometric paint changes how a ship’s shape and heading are judged.
Repeated face-like patterns on fabric try to redirect a face detector towards decoys around the wearer.
A deliberately designed shirt print can make a tested person detector miss a wearer who remains visible to people.
A pattern spread across a garment explores how clothing can confuse a person detector from different angles.
Graphic makeup and hair explore how a visible face can fall outside a particular detector’s expectations.
A flat glass plate reconstructs light from a still life. Move sideways and the objects reveal a different view, as though you were looking through a window.
A lamp illuminates a flat plate and an image appears to occupy depth. The light returns towards the viewer from a recorded structure inside the holographic material.
A hologram becomes visible in ordinary white light. Move sideways to explore depth; move vertically and its colour changes through the spectrum.
A figure appears on an empty stage, transparent enough for the scenery to show through. Its real source is hidden elsewhere.
A shallow frame seems to contain a deep tunnel of lights. A single row of LEDs becomes a chain of reflections that fades into the distance.
Gorillaz’s animated band members appear to perform on stage. Musion’s holographic presentation turns video into an apparently present performer.
Madonna appears to share the stage with Gorillaz during the 2006 Grammys. Her opening appearance is a projected recording, followed by Madonna performing live with her dancers.
A building seems to fold, open or gain impossible depth. Precisely aligned projected images turn its real façade into a moving trompe-l’œil.
Ghosts and skeletons appear in darkness, grow larger and seem to approach the audience. Hidden magic lanterns turn painted slides into an unsettling moving spectacle.
A ghost shares the stage with a living actor, then fades away. Victorian ghost shows turned hidden performers and sheets of glass into public spectacles of apparent presence.
A painted room appears to recede into the wall, although its apparent back wall projects towards the viewer.
Several projecting surfaces join into a convincing painted space whose depth can reverse as the viewer moves.
Three angels gather around a table in a space whose furniture opens towards the viewer instead of following a single distant vanishing point.
A desk opens across a collage of photographs made from different positions. Its surfaces belong to a walk around the subject rather than a single camera view.
An optical illusion is an image or scene that creates a difference between its physical features and the way it is perceived. Context, perspective, contrast and visual adaptation can all contribute to the effect.
Vision interprets light using surrounding shapes, colours, depth cues and prior experience. Illusions reveal situations in which these normally useful processes produce surprising interpretations. Different illusions involve different mechanisms.
Through Mirror includes size and geometry illusions, light and colour effects, ambiguous figures, impossible objects, motion illusions and hidden contours. The collection also explores illusion art, architecture, fractals, animal camouflage and other senses.
Open an entry for its viewing instructions, explanation, history and sources. Gallery images can be enlarged, reversible pictures can be rotated, and animations play when selected. Some demonstrations link to their original source.
An architectural illusion changes the apparent shape, depth or extent of a real place through painting, perspective, geometry or reflection. Its effect often depends on where the observer stands.
The cathedral’s famous apparent dome is a painted illusion by Antonino Emanuele, dating to 1739. The painting makes a flat ceiling appear to rise into a dome from the intended viewpoint.
Forced perspective changes scale and alignment to suggest a different depth or size. Borromini’s corridor at Palazzo Spada uses a compressed construction that appears longer from its intended viewing position.
The collection explores Gary Fisher’s Optical Interactions as a laser transmission example, Matthew Schreiber’s Cassadaga (Spirit Pond) as a reflection hologram, and Stephen Benton’s Sphere as an early white-light transmission example. Diagrams explain each method, with links to the artists’ archives or original exhibition catalogue.
Optical holography encodes and reconstructs a light wavefront using an interference pattern. Pepper’s Ghost and Musion Eyeliner instead reflect an image into the audience’s view, making it appear to occupy the stage. Both can create a convincing presence, but their optical mechanisms differ.
A row of LEDs sits between a rear mirror and a partially reflective front panel. Repeated reflections create successive virtual images that appear farther away. Each loses light, so the apparent tunnel fades even though the frame is shallow.
Musion documents Gorillaz at the November 2005 MTV Europe Music Awards in Lisbon and lists the band’s 2006 Grammy Awards appearance in its portfolio. Eyeliner uses angled transparent foil and video imagery to create the stage illusion.
Projection mapping aligns light with a real object or building. Content that adds convincing perspective, shading or motion can turn that surface into a trompe-l’œil: it seems to gain depth or change shape. URBANSCREEN’s 555 KUBIK is an architectural example.
Her first appearance alongside Gorillaz was prerecorded footage presented through Musion’s reflected-video system. Musion director James Rock described filming it three weeks before the show. The performance then moved to Madonna appearing live with her dancers, so it combines a virtual appearance with a real performer.
Camouflage changes how an observer detects or recognises an organism or object. It includes matching a background, breaking up an outline, masquerading as something else, borrowing cover and confusing judgments of shape or direction.
No. Plants such as Lithops resemble stones. People use camouflage in clothing, face paint, netting, disguised structures and painted ships. Some designs also challenge how computer vision models detect people or faces.
Background matching reduces the visual contrast between an object and its surroundings. Masquerade makes an object resemble something the observer may ignore, such as a leaf, a stone or a tree.
Dazzle patterns were intended to confuse judgments of a ship’s form and course while it remained visible. Their historical effectiveness is difficult to establish; they are different from background matching.
No. Visibility depends on the background, light, distance, movement and the observer’s sensory abilities. A photograph illustrates appearance but does not establish effectiveness in every setting.
Face-like prints can act as decoys for a specific face detector, as explored by HyperFace. The original prototype used a scarf and targeted an older OpenCV detector. Producing false face detections does not prove that the real face is missed or that its identity cannot be matched. A generic face-pattern shirt has no established protective effect.
HyperFace adds face-like decoys around a person. Adversarial shirt research designs prints to change a person detector’s decisions; those prints need not resemble faces. Some studies use a chest patch, while others cover shirts, skirts and dresses with an all-over texture.
Face detection locates a face in an image. Face recognition compares a face with stored identities. Person detection locates the whole person. Confusing one of these tasks does not by itself establish that the other tasks have failed.
No universal effect is established by these examples. Results depend on the target model, camera viewpoint, movement, lighting and fabric deformation. The original HyperFace and CV Dazzle looks targeted older face detectors. The diagrams here explain the ideas and are not tested camouflage patterns.
A fractal is a mathematical structure with detail or related patterns across different scales. Some fractals repeat an exact construction; others show more varied forms of self-similarity.
Not necessarily. Through Mirror includes fractals because their repetition, intricate boundaries and nested patterns challenge visual intuition. Their geometry does not have to create a perceptual error.
The Mandelbrot set is defined by repeatedly applying a mathematical rule to complex numbers and checking whether the results remain bounded. Images show its intricate boundary and related patterns at different scales.
Trompe-l’œil means deceiving the eye. In painting, carefully arranged perspective, shading and familiar objects can make a flat surface appear to contain real depth or objects.
Anamorphosis is a distorted image that becomes recognisable from a particular viewpoint or with an appropriate reflective surface. Holbein’s The Ambassadors includes a skull revealed by an oblique view.
Arcimboldo arranged recognisable objects such as fruit, flowers and books into the features of a face. Some works also reveal a second interpretation when the painting is turned upside down.
Geometric illusions change the apparent size, length, angle or alignment of shapes. Surrounding lines and perspective cues can make equal lengths look unequal or parallel lines appear tilted.
Yes. The horizontal boundaries are parallel, but the alternating arrangement of light and dark tiles makes them appear to slope.
Follow the entry’s instructions, then compare the relevant lengths with a ruler or cover the surrounding context. This can separate the physical measurement from the visual impression.
The visual system judges a surface in relation to nearby contrast and apparent lighting. The same image value can look lighter or darker depending on its surroundings.
Yes. The labelled squares have the same grey value. The depicted shadow and checkerboard context make them appear different; isolating the squares reveals the match.
Mach bands are apparent light and dark strips near changes in brightness. They illustrate how the visual system responds to contrast at boundaries.
A colour afterimage is a lingering visual impression after looking away from a coloured stimulus. Adaptation in the visual system can make a different colour appear against a neutral background.
Colour perception depends partly on surrounding colours and contrast. An unchanged patch can look different when placed in a different visual context.
Use the viewing instructions on the entry page. Look at the specified point, then shift to the suggested neutral area. You can stop whenever you wish; the effect varies between viewers.
An ambiguous figure supports more than one interpretation of the same image. A viewer may switch between the interpretations even though the picture stays unchanged.
The same outline can be read as a duck facing one direction or a rabbit facing the other. The shape that looks like a beak can also look like ears.
The central region can be seen as a vase, while the surrounding regions can be seen as two facing profiles. The shared boundary changes meaning as foreground and background switch.
An impossible object is a drawing whose parts suggest familiar three-dimensional shapes but cannot all connect as they appear to. The contradiction becomes clearer when you trace the whole structure.
It cannot exist as the ordinary solid the drawing suggests. A specially arranged model can create the appearance from one viewpoint, but its actual structure differs from the pictured object.
The drawing joins plausible stair segments into an apparent loop that continually rises or falls. In ordinary space, a closed circuit cannot gain height at every step and return to its starting level.
Certain arrangements of contrast and pattern can produce apparent movement, especially away from the centre of attention. A motion illusion does not always require an animated image.
No. The silhouette has ambiguous depth cues and can be interpreted as turning in either direction. Its perceived rotation does not establish a personality type or a dominant brain hemisphere.
No. Through Mirror initially shows still previews. Open a demonstration and select Play animation when you want to see it move.
Illusory contours are apparent edges that are not explicitly drawn. Surrounding shapes can make a viewer perceive a continuous boundary or a surface.
The bright triangle appears to have clear edges, but those edges are not drawn. The surrounding cut-out shapes suggest a triangle covering parts of them.
Vision uses the relationships between visible edges and surfaces to interpret partially hidden objects. Illusory-contour demonstrations show how a coherent shape can be perceived from incomplete cues.
An auditory illusion is a surprising perception of sound influenced by context, arrangement or interpretation. Examples include ambiguous melodies, apparent changes in pitch, and the virtual barber shop’s impression of a haircut happening around you.
Entries explain the effects and provide listening demonstrations. For Virtual Barber Shop, use stereo headphones with the left and right sides correctly placed, then play the embedded demonstration.
Spatial sound gives audio a sense of direction and distance in three-dimensional space. Binaural audio delivers this through two headphone channels that reproduce cues reaching each ear, including timing, loudness and filtering by the head and outer ears. The virtual barber shop uses these cues to place a barber around your head. Binaural beats are a different effect: nearby tones presented separately to each ear create a perceived beat.
A tactile illusion is a surprising experience of touch or bodily sensation. Adaptation, neighbouring stimulation, body position and expectations can influence what is felt.
Some demonstrations explore touch alone, while others involve interactions between touch and vision. The entry’s instructions explain which senses and conditions are involved.
A multisensory illusion involves interactions between senses. What a person sees, hears or feels can change how information from another sense is interpreted.
The McGurk effect occurs when seeing speech movements influences the speech sound a listener perceives. Combining mismatched visual and auditory speech can produce a different perceived syllable.
