Visual Perception There are two categories of cognitive processes that we use when we assign meaning to incoming information. What are they?

Visual perceptual principles Psychological factors

Visual Perceptual principles include: Gestalt Principles which enable us to perceive forms eg shapes and objects by grouping elements into whole entities Depth Perception which help us determine how far objects are away and enable us to translate 2-dimensional images into 3 dimensional objects Visual Constancies which allow us to perceive a visual stimulus as remaining stable and unchanging despite changes to the retinal image

Gestalt Principles Figure Ground Closure Similarity Proximity What are the four Gestalt principles? Figure Ground Closure Similarity Proximity

Figure Ground Camouflage We tend to separate the important aspects of the visual field (figure) from the surroundings (ground) When the contours are not clearly visible it is difficult to separate the figure from the background. What is it called when it the figure and the background blend together? Camouflage

Proximity What do you see? What do you see? Can you explain the difference? What principle is involved?

Similarity What do you see? What do you see here? Why? What Gestalt principle is involved in your perception?

Closure What do you see? Which principle is involved?

Depth Perception Binocular Monocular Depth cues which are internal and involve the eye and the brain and are known as primary cues. Depth cues which are external and part of the environment and are known as secondary cues. What are the two main types of depth perception cues? Binocular Monocular What is the difference? Binocular cues involve two eyes and monocular cues involve one eye.

Binocular Cues Convergence Retinal Disparity Binocular cues are primary cues and involve the eye. What are they? Convergence Retinal Disparity

What is convergence? Useful for object up to 6m away. To view objects close to us our eyes turn inwards(converge). Changes in muscle tension are detected and interpreted by the brain and used to determine the depth and distance of an object.

What is retinal disparity? As our eye are 6-7cm apart the retinas receive slightly different images. This is true for objects within 10 metres. The retinal images are fused together and compared by the brain. Any disparity between the images provides us with information about the depth of the object and its distance from us.

Monocular Cues Accommodation is a primary cue as it involves the eyes. It involves the focussing mechanism of the lens. What happens to the lens when the object is close? The ciliary muscle contracts and the lens bulges so the image is focussed on the retina What happens to the lens when the object is distant? The ciliary muscle relaxes which flattens the lens so the image is focussed on the retina Information about how much the lens bulges or flattens is used by the brain to determine depth and distance of an object

Monocular Cues Pictorial Cues are secondary cues as they occur in the environment What are the five pictorial cues? Linear Perspective Interposition Texture Gradient Relative size Height in the visual field

What cues for depth has this artist used?

Lady and Gentleman on Horseback, c. 1655 You will achieve the most vivid sense of depth if you view the painting monocularly and through a reduction screen (formed by your hand) to eliminate cues that attest to the actual flatness of the screen. List as many different pictorial depth cues as you can, indicating where they appear in the painting.

Hogarth's False Perspective (c. 1754). look at this picture monocularly. Note that in this picture the two- dimensional portrayal of three- dimensional space is rife with purposeful errors. Thus, it is filled with impossible or highly improbable figures, although they may not seem impossible at first glance. First, describe as many of the errors as you can and indicate the perceptual cues that give rise to the error (and how you know that they are errors). Next, describe what this picture tells you about pictorial cues and the two- dimensional representation of three- dimensional space

In this picture the figure in the white t-shirt was cut out and placed down near the feet of some of the people in the front. Why did you perceive that he was the same size as the people in the foreground of the original picture? Take a look at the photograph below. Do all the people in it all look reasonably the same size. Especially compare the near and far people in the photograph. Size constancy

What are the other types of visual constancy? Shape Brightness Orientation

Look at these figures are they possible?

Is this possible?