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Chapter 4

Chapter 4

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University of Toronto St. George

Chapter 4 - Representation and Knowledge in Long-term Memory Role of Knowledge in Cognition Knowledge is often thoughts of as made of facts, techniques and procedures that cultures develop. Knowledge may come to a person consciously or unconsciously Knowledge is defined as information about the world that is stored in memory, ranging from everyday to the formal It is essential for the competing functioning of mental processes and also plays a role in perception and attention Without knowledge, we cannot categorize things. Categorization is the ability to establish that a perceived entity belongs to a particular group of things that share key characteristics. Failure to categorize, makes a person similar to a camera that can register an image but cannot interpret it Once we are able to categorize an object to a category, further knowledge becomes available about the category. Categorization then allows to draw inferences; provides the ability to expand on the information explicitly present in the image Without knowledge, a person cannot perform an action because he/she would not know how to perform an action Without knowledge, one cannot complete the partial perception of an image, as in when a word is hidden yet we are able to perceive it, therefore knowledge affects perception A memory is useless without knowledge because we would fail to draw useful inferences from the memory Understanding of language requires knowledge; it helps us put together words and understand the meanings of the words Knowledge helps us draw on the principle of transitivity; a relation between three elements such that if it holds between the first and second and it also holds between the second and third it must necessarily hold between the first and third i.e. if A = B, and B = C then A = C This idea of transitivity through knowledge enables sophisticated thought Representations and their Formats Knowledge relies on representations Representation is a physical state that stands for an object, event or concept. It tends to carry the information about what it stands for Memories and Representations A memory helps if it can form a representation There are two criteria for the formation of a representation: i. The intentionality criterion: A representation must be constructed intentionally to stand for something else. Information in the brain may be store consciously or unconsciously mostly we do not try to remember the information presented to us, we just tend to remember it because we have the unconscious motive to remember information about experience. This process has an evolutionary basis, therefore there is a natural intention to remember the information whether we try to consciously process it or not ii. The information carrying criterion: A representation must carry information about what it stands for because it will allow us to categorize the loose images as a single representation. Representations lay the groundwork for knowledge and allow more sophisticated thought processing Four possible formats for Representation An aspect of representation is its format; the type of coding employed. Format refers to the elements that make up a representation, their arrangement and the processes that operate on them to extract information Representations are of two types: i. Modality specific: They make use of perceptual or motor systems ii. Amodal: It resides outside the perceptual and motor modalities Another aspect of a representation is its content; the information it conveys Modality Specific Representations: Images An image has three elements: i. A spatiotemporal window: Our visual system, like a camera, captures the image within a spatiotemporal window. Temporally, the scene is not captured continuously over time but just in one slice of time when the shutter is open. The amount of information captured depends on the spatiotemporal window ii. Storage units: An image contains an array of storage units which are laid out in a grid. Each storage unit is sensitive to the light impinging on it and has its own spatiotemporal window through which it capture information bounded within a spatial and temporal region. iii. Stored information: Across storage units, the collective information specifies the content of the image Additional research shows that human brain actually has images in it The pattern of brain activation on the brains surface roughly depicts the shape of the stimulus presented. The reason is that the cortex of early visual processing area is laid out like the pixels of image and similarly it responds to capture the image. When the neurons within that arrangement fires, the pattern of activation forms a topographical map; the spatial layout of the brain is similar to the layout in space Neural evidence: Research shows that visual images are topographically mapped in the brains occipital lobe. Removal of right occipital lobe resulted in loss of left visual field and within the brain the image size reduced to half of its original size Behavioural evidence: A study was conducted where people were asked to construct mental images and indeed they were able to construct images with perceptual qualities Brain images are not as accurate as a camera image but there is not that uniform level of detail in every aspect of the image but visual attention allows better representation of certain areas and not so good for others Our mental imagery also makes use of the size in the spatial location and then draws the size of the mental image relative to the size of other objects e.g. the study with elephant and goose, goose and fly Therefore, depending on where we focus attention the interpretation of an object varies Mental images are representations within a processing system that interprets them in specific ways to understand the imasgery Modality Specific Representations: Feature Records Sophisticated representation uses the idea of categorizing meaningful entities A meaningful entity is an object or event that plays an important role in an organisms survival or pursuit of goal The meaningful representations are derived from images In a study, it was noticed that the neurons of a frog are particularly sensitive to small objects moving within the visual field and different populations of neurons work to detect different features. Such ability to detect the features such as small, round and moving are important for the survival of a frog Feature is a meaningful sensory aspect of a stimulus Organis
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