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Psychology unit 1 chapter 3 - Visual perception principles

Units 1 and 2 jacaranda by john grivas and linda carter
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Visual perception principles
Rules that we apply to visual information to assist our organization and interpretation of the information. They can be classified as three categories: Gestalt principles, depth principles and perceptual constancies.
Gestalt principles
Gestalt is German for form/shape. Gestalt principles refer to ways we organize a visual image by grouping them together or perceiving them as a whole. We fill in the gaps. Principles include: figure-ground organization, closure, similarity and proximity.
Figure-ground organization
When we distinguish between the figure and the ground. The 'figure' is the foreground which stands out from the background, which is the 'ground'. This is when we separate the figure from the ground using a 'contour', a boundary between the two. It is usually perceived as belonging to the figure. Images which the contour can belong to the figure or the ground, are called reversible figures. e.g. vase + 2 faces. Camouflage is when the contour is indistinguishable. Culture can influence figure-ground organization.
Closure
Closure is when we ignore gaps in an image and fill in the gaps.
Similarity
The tendency to perceive parts of an image that have similar features (such as size or shape) as belonging to a group. e.g. footy teams with uniforms on the football field.
Proximity
The tendency to perceive parts of a visual image which are positioned close together as belonging together in a group. e.g. letters grouped together can be perceived as a word.
Depth perception
The ability to accurately estimate the distance of objects.
Depth cue
Sources of information from the environment (external) or from within our body (internal) that help us to perceive depth. There are two types of depth cues: binocular and monocular.
Binocular depth cues
Requires the use of both eyes. Especially important in determining close objects. There are two binocular depth cues: convergence and retinal disparity.
Convergence
Involves the brain detecting depth from changes in tension in the eye muscles when they turn inwards to focus on close objects.
Retinal disparity
Refers to the very slight difference (disparity) between each of the retinas due to the angles from which they view the visual information. The two images are compared in the brain and this determines depth.
Monocular depth cues
Requires one eye, but can also operate with both eyes. Monocular depth cues include: accommodation and pictorial cues.
Accommodation
Involves the automatic adjustment of the lens using ciliary muscles to focus an object depending on its distance.
Pictorial cues
Artists use these to create depth and distance on a two dimensional surface. These include: linear perspective, interposition, texture gradient, relative size and height in the visual field.
Linear perspective
The convergence of lines as they go back into the distance.
Interposition
Also called overlap, is when one object partially blocks another and is perceived in front of the blocked object.
Texture gradient
Refers to the gradual reduction of detail as a surface recedes into the distance.
Relative size
Refers to the tendency to perceive the largest object as being closer, however the objects must be the same size in real life. We take into account past experiences that let us judge their size.
Height in the visual field
Refers to the location of objects in vision, objects that are closer to the horizon are perceived as more distant.
Perceptual constancies
Refers to the tendency to perceive an object as remaining constant despite any changes that may occur in the image. These include size shape and brightness constancies.
Size constancy
Size constancy involves recognising that an object's actual size remains the same, even though the size of the image changes. e.g. train coming towards you gets bigger but we perceive it as the same size in real life.
Shape constancy
Shape constancy is the tendency to perceive an object as maintaining its shape despite any change in shape of the image of the object on the retina. e.g. the angle of which we view the clock face changes, and subsequently the image changes as well, but we perceive the clock as being constant in shape.
Brightness constancy
The tendency to perceive an object as maintaining its level of brightness in relation to its surroundings. e.g. the brightness in the room changes, but we perceive that all the objects remain the same colour.