1 - Visual Agnosia: A deficiency in the ability to recognize visual information despite
being able to see.
2 - Associative Agnosia: A form of visual agnosia marked by a difficulty naming
3 - Time Spaces: The perceptual experience of time units such as days of the week
or months of the year as occupying special locations outside of the body.
4 - Perception: Processing sensory information such that it produces a meaningful
understanding of the information.
5 - Stimulus: An entity in the external environment that can be perceived by
6 - Theory of Ecological Optics: The proposal that perception involves directly
absorbing the visual information present in the environment.
7 - Ambient Optical Array (AOA): All the visual information that is present at a
particular point of view.
8 - Texture Gradients: Gradual changes in the pattern of a surface that is normally
assumed to be uniform, which provides information about surface characteristics
such as whether the surface is receding or curved.
9 - Topological Breakage: The discontinuity created by the intersection of two
10 - Scatter-Reflection: The degree to which light scatters when reflected from a
11 - Transformation: In the theory proposed by Gibson, the change of optical
information hitting the eye when the observer moves through the environment.
12 - Optic Flow Field: The movement of objects or of the observer through the
environment produces changes in what is seen.
13 - Percept: Meaningful interpretation of sensory information.
14 - Memory Trace: The trace that an experience leaves in the brain.
15 - Höffding Function: When an experience makes contact with a memory trace,
resulting in recognition.
16 - Pattern Recognition: The ability to recognize an event as an instance of a
particular category of events.
17 - Template: A model against which a stimulus is compared to determine whether
it belongs to a particular category.
18 - Prototype: A model that posses all the typical characteristics of its class.
19 - Template-Matching Theory: Comparing a stimulus with template; when they
match the stimulus is recognized as belonging to that category.
20 - Multiple-Trace Memory Model: Traces of each individual experience are recorded
in memory. No matter how often a particular kind of event is experienced, a
memory trace of the event is recorded each time.
21 - Probe: Secondary memory can be activated by means of a probe from primary
22 - Echo: When a probe goes out from primary to secondary memory, memory traces
are activated to the extent that they are similar to the probe. Chapter3:Perception.Cognition
23 - Feature Detection theory: Detecting patterns on the basis of their individual
24 - Pandemonium: A model of pattern recognition consisting of three levels: data,
cognitive demons, and decision demons.
25 - Feature: A component or characteristic of a stimulus.
26 - Cognitive Demon: A feature detector in the pandemonium model that decides
whether the stimulus matches its pattern.
27 - Decision Demon: A feature detector in the pandemonium model that
determines which pattern is being recognized.
28 - Contrast Energy: The degree of contrast between letters in a word and the
background they appear on leading to the relative ease with which a stimulus
can be discriminated from the background against which it is displayed.
29 - Sequelching: The tendency of the nervous system to inhibit the processing of
30 - Geons: The basic geometric shapes that comprise objects.
31 - Recognition by Components (RBC): A model of perception based on subdividing
objects into a basic set of geometric shapes.
32 - Recoverability: the degree to which geons can be made out in a degraded image
of an object.
33 - Top-Down (User-Driven) Processing: When perception (or other cognitive
processes) is driven by expectations and prior knowledge.
34 - Context Effects: The influence that the situation plays on the perception of a
35 - Bottom-Up (Data-Driven) Processing: When perception (or other cognitive
processes) results from the combination of individual pieces of sensory
36 - Moon Illusion: The tendency for the moon to appear larger when on the horizon
than when high in the sky.
37 - Apparent-Distance Theory: An explanation for the moon illusion; it posits that
the moon on the horizon appears larger because ‘distance’ cues lead the
observer to perceive it as being nearer that the zenith moon.
38 - Angle-of-Regard Theory: A theory developed to explain the moon illusion, which
states that the zenith moon appears smaller than the horizon moon because a
person has to raise his or her eyes or head to view it.
39 - Jumbled word Effect: The ability to read words in sentences despite having
mixed up letters in the middle of some words.
40 - Parallel Distributed processing (PDP): A model of perception that proposes that
different features are processed at the same time by different units connected
together in a network.
41 - Word Superiority Effect: It is easier to identify a letter (e.g. D) if it appears in
a word (e.g. WORD) than if it appears alone.
42 - Empirical Theory of Colour Vision: The proposal that colour perception involves
not only the processing of wavelengths of light but also the influence of prior
experiences about how different lighting conditions affect the appearance of the
colours of objects.
43 - McGurk Effect: The auditory experience of the syllable ‘da’ when seeing a mouth
silently saying ‘ga’ while the same time hearing a voice say ‘ba’. Chapter3:Perception.Cognition
44 - Change Blindness: The common failure of people to notice changes to an object or
45 - Grand illusion of Perception: The experience of a clear and detailed picture of
the world in one’s visual field.
46 - Feature Integration Theory (FIT): Before we can attend to objects in the world
we must extract the features that make up these objects.
47 - Preattentive Processing: Automatic extraction of features before an object can
48 - Feature Binding: The combining of visual features by attention to form whole
49 - Attentive Processing: Combining features into a whole object through attention.
50 - Pop-Out: Grab attention.
51 - Blind Spot: A region in the eye where the optic nerve leaves the retina; it does
not contain any photoreceptors.
52 - Perceptual Completion (Filling-In):
53 - Gestalt Psychology: A branch of psychology that focuses on dealing with wholes
rather than parts.
54 - Bi-Stable Figures: Images from which to separate percepts can be formed.
55 - Figure-Ground Segmentation: Perceptual organization of a scene such that one
element becomes the foreground (figure) and the other element(s) become(s)
the background (ground).
56 - Holistic: Focusing on the whole configuration of an object. Chapter3:Perception.Cognition
57 - Atomistic: Focusing on the features or components of objects.
58 - Organizational Principles: The rules that explain the ways in which people are
able to perceive whole objects or events from individual parts.
59 - Group: The way in which individual parts are combined to form a whole.
60 - Principle of Experience: A principle of Gestalt organization stating that elements
are grouped based on the prior experience and knowledge or the observer.
61 - Denotivity: the degree to which an object is meaningful and familiar to an
62 - Principle of Proximity: Things that are near one another are grouped together.
63 - Principle of Closure: Things that form closed shapes are grouped together.
64 - Principle of Good Continuation: Things that form continuous lines are grouped
65 - Principle of Similarity: Things that are similar are grouped together.
66 - Principle of Common Fate: Things that are moving in the same direction are
67 - Ceteris Paribus: A Latin term that means ‘when all is equal’.
68 - Gestaltist’s Error: The assumption that whole objects should always dominate
over the elements of an image.
69 - Apperceptive Agnosia: A form of visual agnosia marked by a difficulty matching
or categorizing objects.
70 - Optic Ataxia: A neural deficit in which the patient can identify objects but is
unable to accurately interact with them manually. Chapter3:Perception.Cognition
71 - Prosopagnosia: An impairment in the ability to recognize faces despite intact
recognition of other objects.
72 - Skin Conductance Response: The small increase in the conductivity of the
surface of the skin when an individual is aroused by seeing a familiar object or
73 - Capgras Syndrome: A condition marked by the belief that significant others have
been replaced by imposters, doubles, robots, or aliens.
Perception researchers explore a wide variety of fascinating phenomena. Here are
(1) Visual agnosia: This phenomenon relates to a set of perceptual experiences.
Theses experiences can occur to someone who has sustained a head injury or a
stroke, for example.
Context: You wake up, after some kind of brain trauma, and your able to see all the
objects that surround you, but you can’t recognize or identify any of them.
Visual agnosics don’t have a sensory impairment; they just can’t cognitively
interpret the information they see. Actual example reported by H. Lissauer: the
patient. Lissauer reported a description of an 80-years-old patient experiencing
perceptual deficits, as a result of brain damage. Here is a sample of the type of
responses the patient gave when presented with simple visual objects:
(Object presented: a lamp containing a light) Patient: A figure.
Interviewer: What does it represent?
Patient: That, I can’t guess. It could be a man. But the figure only goes up to there (shows
the length of the light). The other (shows the lamp) is something fixed, a base.
Interviewer: Is it really a man and not perhaps a column?
Patient: No, here are his head and his legs. Here is even a bent leg (shows the bent wick of
the light). Chapter3:Perception.Cognition
(For other examples see page 49).
Note that the patients sometimes identify some objects correctly, thus demonstrating
that visual recognition is not always completely impaired. Visual agnosia is also specific to
the visual domain. When presented with everyday objects (like a brush), patients can
identify them by means of using other senses (like touch).
One form of agnosia is associative agnosia, where patients have trouble identifying objects
that they see even though they have the visual ability to reproduce the objects by drawing
them. (see figure 3.2 – studied by Rubens and Benson)
(2) When individuals with time spaces hear or see the names of various units of time such
as days, weeks, and months, they experience seeing them in spatial patterns external to
themselves. Francis Galton has studied these perceptual experiences. (Experience of time
space is illustrated in figure 3.3) That example implies an individual that experiences the
months in an oval form, which is seen 30 cm in front of her face. Other individuals
experience their time spaces as surrounding them at about waist height; for some, their
time space rotates with them every time they rotate their torso. It goes wherever they
These experiences occur automatically and therefore, can’t be consciously inhibited.
People with time space often report to use them like a calendar to remember important
Cognitive psychologists studying perception investigate:
1 How sensory information is processed,
2 How conscious experiences related to the senses emerge, and
3 How information in the environment guides action in the world.
Note that perception can occur in any modality and involve any of our sensory
organs. A critical distinction to keep in mind is about the dependency of perception Chapter3:Perception.Cognition
on both the external environment (i.e. the stimulus) and the internal knowledge of
Perception as a Function of the Environment
Gibson’s theory of ecological optics focused on the idea that in real-world
situations, the sensory organs receive a complex array of information that can be
directly apprehended and used to guide actions. “Perception is the function of
stimulation and stimulation is a function of the environment” (Gibson). He didn’t see
the need for the organism to create complex internal mental representations of
objects; rather, he argued that perception is accomplished mostly by the sensory
Gibson pointed to the patterns in light that reflected from surfaces and the objects
around us. He referred to this as ambient optical array (AOA), or the ambient array. He
1 From every viewing point, a unique pattern of light enters the eyes because it is
reflected from and emitted by a unique combination of surfaces.
2 Environment is textured and textures consist of repeated patterns, which
formed texture gradients. (See figure 3.4: the change in the pattern, which is
normally believed to consist of equally sized stones, is interpreted as a surface that
is going away from the observer, with smaller stones being perceived as being
smaller because they’re far away).
3 When two different textures intersect, they create a discontinuity in the
pattern called topological breakage. Topological breakage provides useful indicator
for edges of objects.
4 Different degrees of smoothness reflect light in different ways and the nature
of the reflected light thus provides useful information about the smoothness of
the surface. (See figure 3.5: a rough surface reflects light more widely than a
smooth surface). How widely light is scattered is referred to as scatter- Chapter3:Perception.Cognition
reflection. Scatter-reflection from object tells us a lot about the nature of the
A critical aspect of Gibson’s paradigm was that he included observer and
environment motion as a fundamental component of perception. He argued that
much of the classical theories and experiments relied on the assumption of a fixed,
An example of that is a trapezoidal frame can be made to appear rectangular, but
as soon as you let the observer move, even subtly, the illusion vanishes. Gibson
believed that as the observer moves, the entire optical array undergoes a change.
This change in the way of all surfaces project light on the retina is referred to as
transformation of the optic array. The focus on movement led to the concept of
the optic flow field (the continually changing pattern of information in the AOA
that results from the movement of objects or the observer through an
An every day example is the view from you car while driving. When you look out the
front windshield while driving, the objects straight in front of you if you’re facing
the direction you are moving appear almost stationary while near objects closest to
the edges of your visual field appear to be moving by quickly.
Gibson was strongly reacting against studies that relied on visual illusions as a
means of learning about perception. He believed that illusions revealed aspects of
vision that were not particularly relevant for everyday life; he was more interested
in studying situations where an individual is moving and directly picking up
information from a complex, changing world.
Gibson’s contributions were vital in pulling attention away from the simplified, reductionist
stimuli of his time and to the dynamic, meaning-laden environment of the real world, urging
new approaches to understanding the relations between environment, perception, and
Theories of pattern recognition differ from Gibson’s view in at least two ways:
1. (1) They don’t consider the complex array of light information reflecting from all
surfaces and objects. The focus is primarily on specific objects or patterns.
2. (2) They focus on how it is that we build internal representation of objects during
the process of recognition, while Gibson focused on how information is directly
The phrase pattern recognition came from computer science, where it refers to a
computer ability to identify configurations such as the account numbers on bank cheques.
People are also able to identify many configurations with which they are presented.
Recognizing a configuration involves contact between the emerging percept and memory
(see figure 3.7). This process is called the Höffding Function. Suppose you are shown the
latter ‘a’ on one occasion: we can imagine a sequence of events whereby you are forming a
percept of the letter ‘a’, and then a memory trace of the letter is formed. In order to
recognize the letter ‘a’ your emerging perception of ‘a’ must somehow make contact with
the memory trace of ‘a’.
According to the Oxford Dictionary, the word template originally meant a ‘gauge or a guide
to be used in bringing a piece of work to its desired shape’. Such a guide might have edges
corresponding to the outline of the finished product. For example, is you were painting
letters, you might make a cut-out, or a stencil, of the letters you wanted to paint: the cut-
out is the template. It is possible that we store templates in our memory that correspond
to the standard forms of the configurations we see. The process of template matching
would involve comparing the current configuration with the standard in memory. The
standard can be a specific memory of an object or a prototype of the object, which is the Chapter