Perception

Perception Perception is the process by which the brain analyses and makes sense of the incoming sensory information. Sensory information comes in to the brain through visual, auditory, olfactory, tactile (skin) and chemoreceptors in the sense organs. All the senses contribute to the perception of the world but visual perception is particularly important and will be focused on.

Visual perception Visual perception allows a person to do 3 things: To segregate objects from one another and from their background (segregation of objects). To judge how near or far various objects are situated from a person (depth perception). To recognise different objects.

Segregation of objects This is an important first stage in the development of visual perception which includes determining shape. It involves 2 important aspects of perception: The ability to organise into figure and ground The ability to organise into coherent patterns

Figure and ground In any visual picture the brain will organise the information perceptually into figure and ground. The figure or figures will stand out from the background especially if the image has obvious contrasting components. The rest of the image will form the ground. This distinction is sometimes easy to perceive but at other times it can be difficult. The brain will attempt to compare the image with previous images which may be dissimilar but might be very similar.

Coherent patterns The brain will attempt to organise visual stimuli into coherent patterns. Even dots and lines will be ordered into a relationship in an attempt to get a coherent pattern. The coherent patterns of organisation are thought to be along the lines of the following patterns: Proximity Similarity Closure Orientation Simplicity

Coherent patterns Proximity Visual stimuli that are close together are perceived as part of the same object. Stimuli that are further apart are perceived as separate objects Similarity Visual stimuli are organised into groups based on colour, size, shape, and tone If the stimuli are similar they will be grouped together, if not they will be grouped separately

Coherent patterns Closure If the visual stimulus is incomplete or partially hidden by another object the brain will fill in the missing pieces. This is the process of closure and gives perception of a whole object from pieces of a visual stimulus Orientation The brain will organise the perception of visual stimuli into one object if the elements of the group are all seen to be moving in the same direction at the same rate e.g. flocks of birds Simplicity The brain will organise visual stimuli into the simplest previously stored image.

Perception of distance Perception of distance relies on a number of visual cues including: Relative size Superimposition Relative height in the horizontal field Linear perspective Perception of distance is also possible due to the binocular disparity and perceptual constancy

Perception of distance Relative size - the further away an object is from the eye the smaller it is perceived to be. Superimposition – if an object partially blocks the view of another object, then the object that is blocked partially from view is perceived to be further away. Relative height in the horizontal field – the perception of objects that are grouped or linear and whose base is below the horizon is based on their height in the field. Their height in the field will appear to be higher (closer to the horizon) the further away they are. Linear perspective – parallel lines like tracks and rods seem to converge as they get further away

Binocular disparity This means that humans have two eyes which give a slightly different view of an object These 2 images will be more different the closer the object is, due to the way light travels in straight lines. The brain processes these, fusing them together to produce a binocular image. This enables depth and distance from the object to be judged more effectively than using only one image (monocular)

Perceptual constancy The brain has the ability to keep the visual perception stable despite changes in the view. This is particularly important in the perception of size and shape constancy

Perceptual constancy Size constancy Objects are perceived to remain constant in size even when the distant object changes. This is due to past experience, stored knowledge and the relative size cue. Shape constancy Objects are perceived to retain their shape even when the angle they are viewed from changes their image. This is thought to depend mostly on past experience and stored knowledge.

Recognition Object recognition is based on actual shape, perceived shape matching and perceptual set. Shape Object recognition is based on the objects physical properties including shape, colour and texture. Shape is considered to be the most important of these. In early learning the shape of an object allows it to be characterised and differentiated from other objects. This is stored in the long term memory. The general shape is the most important feature, with viewing and feeling the edge of the object also being important

Recognition Matching perceived shape The shape of a viewed object is compared to stored images for a match. If a match is found the shape is quickly identified. If no match is found a blank is drawn. The brain may recognise the object as similar to other stored images. It may infer that the image is related to other objects and group it with them until further information becomes available.

Perceptual set This is the brains ability to perceive some aspects of the available sensory information but ignore others. This is determined by an individual’s expectation, context and past experience, Expectation – the brain perceives the image in relation to what is expected based on past experience. Context – the brain perceives the image in relation to the surrounding image which gives it context. Past experience – the present image is perceived in relation to previous experience images. Recognition from a previous image will influence the perception of a new image or stimulus

What can you remember? What is perception? What 3 things does human visual perception allow? What are the 2 aspects of segregation? Name 3 of the ways patterns are organised by the brain? For each of these explain what the brain is doing. What are the visual cues for the perception of distance? What is binocular disparity? How does it help with the perception of distance? What 2 things about a viewed object does the brain keep constant? What are the 3 things that object recognition is based on? Explain how the brain uses these.

Consolidation on perception Complete points 1-7 on the summary Complete the matching test part 1 p115 in the multiple choice book Complete the multiple choice questions 1-6 in the multiple choice book pages 116-118.