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Chapter 3-12

PSYCH207 Chapter Notes - Chapter 3-12: Retrograde Amnesia, Anterograde Amnesia, Sensory Memory

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Module 3: Perception - pp. 56 - 96
Perceiving Objects and Recognizing Patterns
Perception: the interpretation of sensory information to yield a meaningful description or
the central problem of perception is explaining how we attach meaning to the sensory
information we receive
the vast topic of perception is subdivided into visual perception, auditory perception,
olfactory perception, haptic (touch) perception, and gustatory (taste) perception
each subject is a distal stimulus
for a living organism to process information about these stimuli, it must first receive that
information through one or more sensory systems - e.g. the visual system
the reception of information and its registration by a sense organ make up the proximal
the meaningful interpretation of the proximal stimulus is the percept - your interpretation
that the stimuli are trees, cars, people, and so forth
percepts are not the same things as proximal stimuli
Gestalt Approaches to Perception
the segregation of the whole display into objects (also called the figure) and the
background (also called the ground) is an important process known to cognitive
psychologists as form perception
Gregory who studied the phenomenon subjective contours (illusory contours) believed
that this relatively complex display is subject to a simplifying interpretation the perceiver
makes without even being aware of making it
Gestalt principles of perceptual organization: laws that explain the regularities in the
way people come to the perceptual interpretations of stimuli. The emphasis is on the
apprehension of whole structures rather than on the detection and assembly of parts of
othe principle of proximity, or nearness → we group together things that are nearer
to each other
othe principle of similarity → group those elements that are similar
othe principle of good continuation → we group together objects whose contours
form a continuous straight or curved line
othe principle of closure → mentally filling the gap to see a closed, complete whole
othe principle of common fate → elements that move together will be grouped
Law of Pragnanz: this law states that of all possible ways of interpreting a display, we will
tend to select the organization that yields the simplest and most stable shape or form
Bottom-Up Processes
bottom-up (or data-driven) essentially means that the perceiver starts with small bits of
information from the environment that she combines in various ways to form a percept
in top down (also called theory-driven or conceptually driven) processing, the perceiver’s
expectations, theories, or concepts guide the selection and combination of the
information in the pattern recognition process
bottom-up processes are relatively uninfluenced by expectations or previous learning
(the so called higher-level processes)

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Template Matching
templates: a stored pattern or model to which incoming information is matched in order
to be recognized and classified
every object, event, or other stimulus that we encounter and want to derive meaning
from is compared to some previously stored pattern, or template
the process of perception thus involves comparing incoming information to the templates
we have stored, and looking for a match
template-matching models thus have to explain how and when templates are created
and how we keep track of an ever growing number of templates
Featural Analysis
instead of processing stimuli as whole units, we might instead break them down into
their components, using our recognition of those parts to infer what the whole represents
the parts searched for and recognized are called features
Neisser had participants perform a visual search task in which researchers presented
them with arrays of letters. The researchers asked them to respond if they detected the
presence of a particular target, such as the letter Q. Shown an array participants took
much longer to find a Z than they did to find a Q. The nontarget letters in array (A) all
share features like straight and angular lines, whereas those in array (B) share features
such as roundness. Similarity between the target letter (Z or Q) and the nontarget letters
can make the search much harder
Selfridge developed a model for the perception of letters that was based on featural
analysis. The model was called Pandemonium
the model illustrates a number of important aspects of featural analysis. Some features
matter more than others in pattern recognition.
Prototype Matching
one that attempts to correct some of the shortcomings of both template-matching and
featural analysis models is known as prototype matching
such models explain perception in terms of matching an input to a stored representation
of information, as do template models
in this case, however the stored representation, instead of being a whole pattern that
must be matched exactly or closely, is a prototype, an idealized representation of some
class of objects or events
they do not require that an object contain any one specific feature or set of features to be
instead, the more features a particular object shares with a prototype, the higher the
probability of a match
prototype models take into account not only an object’s features or parts but also the
relationships among them
Top-Down Processes
context effect: the effect on a cognitive process of the information surrounding the
target object or event. Sometimes called “expectation effect” because the context is
thought to set up certain expectations in the mind of the cognitive processor
Marr believed that visual perception proceeds by constructing three different mental
representations, or sketches
othe first, called a primal sketch, depicts areas of relative brightness and darkness
in a 2D image as well as localized geometric structure

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oonce a primal sketch is created, the viewer uses it to create a more complex
representation, called a 2 ½-D (two and a half dimensional) sketch
ousing cues such as shading, texture, edges, and others, the viewer derives
information about what the surfaces are and how they are positioned in depth
relative to the viewer’s own vantage point at that moment
o3D sketch of the visual scene involves both recognition of what the objects are
and understanding of the meaning of the visual scene
Change Blindness
a recent area of research in visual perception that provides a startling demonstration of
the role of top-down processes in perception concerns a phenomenon known as change
one of the first demonstration of change blindness, the inability to detect changes to an
object or scene especially when given different views of that object or scene, came from
the lab of UBC
The Word Superiority Effect
participants could much more accurately identify letters presented in the context of
words than the same letters presented alone or in the context of nonwords
letters are apparently easier to perceive in a familiar context (a word than in an
unfamiliar context or in no context at all
A Connectionist Model of Word Perception
presented by McClelland and Rumelhart (1981)
the model assumes that input - whether written, spoken, or of higher level, such as
arising from the context or the observer’s expectations - is processed at several different
levels, whether in terms of features, letters, sounds or words
each level of processing is assumed to form a representation of the information at
different level of abstraction, with features considered less abstract than letters, and
letters less abstract than words
Direct Perception
constructivist approach to perception: it describes people as adding to and distorting
the information in the proximal stimulus to obtain a percept, a meaningful interpretation
of incoming information. people are not seen as passively taking in all the available
information; instead, they are seen as active selectors, integrators, and constructors of
direct perception, the light hitting the retina contains highly organized information that
requires little or no interpretation
organisms directly perceive not only shapes and while objects but also each object's
affordances - the “acts or behaviours permitted by objects, places, and events”- in other
words, the things offered by the environment to the organism
Disruptions of Perception: Visual Agnosias
impairments in the ability to interpret (although seeing) visual information
apperceptive agnosia - able to process a very limited amount of visual information, they
can see contours or outlines of a drawing or object but have a very difficult time
matching one object to another or categorizing objects
associative agnosia - patients with this deficit can match objects or drawings and copy
drawings, but tend to do so very slowly and very, very carefully, almost point to point
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