PerceptionPertemuan 5

Matakuliah : L0014/PsikologiTahun : 2007

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PERCEPTION(1)http://en.wikipedia.org/wiki/Perception

• Definition :– is the process of acquiring, interpreting, selecting, and organizing sensory

information – The process of organizing and intepreting information received from the outside

world

• Perception is one of the oldest fields within scientific psychology, and there are correspondingly many theories about its underlying processes. The oldest quantitative law in psychology is the Weber-Fechner law, which quantifies the relationship between the intensity of physical stimuli and their perceptual effects. It was the study of perception that gave rise to the Gestalt school of psychology, with its emphasis on holistic approach. .

• Sensory is a system that consists of a sensory cell type (or group of cell types) that responds to a specific kind of physical phenomenon, and that correspond to a defined region (or group of regions) within the brain where the signals are received and interpreted

• Stimulus : any aspect of the outside world that directly influences our behavior or conscious experience

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1. Visual Perception2. Multisensory Integration3. Motivation, Emotion and Perception

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VISUAL PERCEPTIONPerceptual Organization

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VISUAL PERCEPTION

• What We perceive is often based on how sensory information is processes in our brains than what is in front of our eyes (Long & Toppino, 2004)

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VISUAL PERCEPTIONPerceptual Organization

1. Figure GroundPart of visual stimulus will be the center of our attention (figure) and the

rest will be the indistinct ground. Sometimes the figure and the ground can be reversed in our perception of the same stimulus

2. ContinuityThe lines or patterns that follow the smooth contour will be perceived as

part of a single unit3. Proximity

Parts of a visual stimulus that are close together will be perceived as belonging together

4. SimilarityParts of visual stimulus that are similar will be perceived as belonging

together5. Closure

The Incomplete figures of familiar objects will tend to be perceived as wholes

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FIGURE GROUND

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CONTINUITY

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PROXIMITY• This that are close together are usually perceived

as belonging together

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SIMILARITY (1)

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SIMILARITY (2)

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CLOSURE

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VISUAL PERCEPTIONDepth Perception

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VISUAL PERCEPTIONDepth Perception (1)

• Retina has 2 – dimensional surface : up – down, left – right• Monocular cues to depth perception can be perceived by

one eye

• 8 monocular cues :1. Texture gradient2. Linear perspective3. Superposition4. Shadowing5. Speed of movement6. Aerial perspective7. Accommodation8. Vertical position

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TEXTURE GRADIENT (1)

• The texture of object is larger and more visible up close and smaller the far away

• On curve surfaces, the elements of texture are more slanted when the surface does not squarely face us

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TEXTURE GRADIENT (2)

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TEXTURE GRADIENT (3)

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LINEAR PERSPECTIVE

• Objects cast smaller images on the retina when they are more distant

• The parallel line appear to grow closer together the farther away they are from us

• Objects with larger relative size appear to be closer than objects with smaller relative size

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SUPERPOSITION

• Closer objects tend to be partially in from of, or partially cover up, more distant objects

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SHADOWING

• The shadows cast by objects and highlights of reflected light suggest their depth

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SPEED OF MOVEMENTObject farther away appear to move across the field of vision more slowly than do the closer objects

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AERIAL PERSPECTIVE• Aerial perspective or atmospheric

perspective is the effect on the appearance of an object by the atmosphere between it and a viewer (or the technique of depicting this effect in a work of art, such as a landscape painting). As the distance between an object and a viewer increases, the contrast between the object and its background decreases. The contrast of any markings or details on the object also decreases. The colors of the object also become less saturated and shift towards blue.

• Aerial perspective was discovered and named by Leonardo Da Vinci, who used it in many of his works, such as the Mona Lisa, in order to suggest distance. In such early paintings the distant objects tend to be represented as gray-green.http://en.wikipedia.org/wiki/Aerial_perspective

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ACCOMODATION• The shape of the lens of the eye must change to

focus the visual image on the retina from stimuli that are different distances from the eye.

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VERTICAL POSITION

• When objects are on the ground, the farther they appear to be below the horizon, the closer they appear to be to us

• For the objects in the air, the farther they appear to be above the horizon, the closer they appear to be to us

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• Binocular Cues in depth perception can only perceived using two eyes

1. ConvergenceWhen both eyes are looking at an object in the center of

the visual field, they must angle inward more sharply for a near object than for a distant object

2. Retinal DisparityThe principle behind the old fashion stereopticon

VISUAL PERCEPTIONDepth Perception (2)

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CONVERGENCE• When both eyes are looking at an object in the

center of the visual field, they must angle inward more sharply for a near object than a distant object.

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RETINAL DISPARITY

• Our eyes are couples of inches apart, they do not see the same view of 3-dimentional objects, especially when the object is close.

• The difference between the images on the 2 retinas is a key factor in depth perception

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VISUAL PERCEPTIONVisual Illusion

• Visual stimuli in which the cues used in visual perception create false perception

• An optical illusion is always characterized by visually perceived images that, at least in common sense terms, are deceptive or misleading. Therefore, the information gathered by the eye is processed by the brain to give, on the face of it, a percept that does not tally with a physical measurement of the stimulus source.

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VISUAL ILLUSIONS (1)

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VISUAL ILLUSIONS (2)

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VISUAL ILLUSIONS (3)

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PONZO ILLUSION• The Ponzo illusion is an optical illusion

that was first demonstrated by the Italian psychologist Mario Ponzo (1882-1960) in 1913.

• He suggested that the human mind judges an object's size based on its background.

• He showed this by drawing two identical lines across a pair of converging lines, similar to railway tracks. The upper line looks longer because we interpret the converging sides according to linear perspective as parallel lines receding into the distance.

• In this context, we interpret the upper line as though it were farther away, so we see it as longer – a farther object would have to be longer than a nearer one for both to produce retinal images of the same size.

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THE ZOLLNER ILLUSION• a classic optical illusion named

after its discoverer, German astrophysicist Johann Karl Friedrich Zöllner.

• In this figure the black lines seem to be unparallel, but in reality they are parallel. The shorter lines are on an angle to the longer lines. This angle helps to create the impression that one end of the longer lines is nearer to us than the other end.

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THE MϋLLER-LYER ILLUSION

• an optical illusion consisting of nothing more than an arrow.

• occurs because the visual system processes that judge depth and distance assume in general that the “angles in” configuration corresponds to an object which is closer, and the “angles out” configuration corresponds to an object which is far away.

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THE AMES ROOM (1)

• The distorted room seen above is named after the American ophthalmologist Adelbert Ames, Jr., who first constructed such a room in 1946. He based his design on a concept originally conceived by Hermann Helmholtz in the late 19th century.

• There are two illusions associated with the Ames Room. First the room appears cubic when viewed monocularly from a special viewing point (the true shape of the room is trapezoidal). Secondly, within an Ames Room people or objects can appear to grow or shrink when moving from one corner to the other.

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THE AMES ROOM (2)• When you look (through a peephole

-- to remove any cues from stereopsis) into an Ames Room, the room looks normal and cubic, but its true shape is cleverly distorted. The floor, ceiling, some walls, and the far windows are actually trapezoidal surfaces. Although the floor appears level, it is actually at an incline (the far left corner is much lower than the near right corner). The walls appear perpendicular to the floor, although they are actually slanted outwards.

This diagram shows how the Ames Room forms an identical image of a normal cubic room on your retina. If a straight line (representing a ray of light) is drawn from one corner of an imaginary cubic room to your eye, the corner can meet this ray at any point along its length and still appear cubic

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POGGENDORF ILLUSION• The Poggendorf illusion is one of the most

famous distortion illusions known. Although much has been written about it since its discovery in 1860, the underlying mechanism that gives rise to this effect is still not well understood.

•      An adequate explanation of the Poggendorf illusion must take all the above factors into account, as well as several others. For example, the Poggendorf illusion is not confined to two-dimensional representations: It also occurs with three-dimensional objects. Secondly, perspective cues can have a drastic effect on diminishing the effect of this illusion.

•      While the Poggendorf illusion is over 100 years old (it was discovered in 1860), there have been no end of theories to try to account for it. Recently, interactive versions have revealed new characteristics and variations of this illusion.  There is, unfortunately, no theory to date that will adequately account for all the variations perceived.

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VISUAL PERCEPTIONColor Perception

• The perception of color is based on more than the information that reaches the brain about the wavelengths of light that reach the cones

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COLOR PERCEPTION (1)

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COLOR BLIND

Color blindness, (also known as Dyschromatopsia) or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain chemicals.

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MULTISENSORY INTEGRATION

• Integrate and interpret information from multiple senses at the same time (Ernst & Bulthoff, 2004)

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MOTIVATION, EMOTION AND PERCEPTION

• Motivation influence perception– Hungry taste the food more delicious

• Emotion influence perception– Anxious hear the ambiguous statement more

threatening