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Chapter 4

Chapter 4 Notes

Course Code
George Cree

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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
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:

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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 brain’s 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

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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 brain’s 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
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
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
organism’s 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
Organisms very well detect the features that need to respond to and do not respond to
every bit of information like a pixel. The neurons just do not capture the aspect of a
image but interpret the region of the image as an important feature.
When the feature-detecting neurons become active, they categorize the part of an
image as a meaningful feature
Feature detection is not just carried by individual neurons but by a population of
neurons and they may be sensitive to more than one feature
The feature detection allows graded reponse (one that varies in degree) than an all-
or-nothing response
Feature detecting neurons successfully make up a representation since they meet the
criteria of intentionality (intention to detect a particular feature for the achievement of
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