Perception and Attention
Advanced Cognitive Psychology
PSY 421, Fall 2004
Overview
 Misperception – An Example
 Sensation
 Perception
 Attention
(Mis)Understanding Visual Perception
 Assignment – draw
lines from the eye to the
object and explain how
the eye “sees” the
object
Extramission Theory of Visual Perception
 Jane E. Cottrell and
Gerald A. Winer (multiple
publications)
 Extramission Theory =
there are emanations from
the eyes during the act of
seeing
 Intromission Theory =
there is only input to the
visual system and that this
information alone allows
people to see.
Percent Responding
Intromission
Extromission
1st
graders
54%
49%
3rd
graders
60%
70%
5th
graders
31%
51%
College
students
88%
33%
Our Class
22.5%
67.5%
Sensation, Perception, and Attention
 How the cognitive system “registers” information
 Sensation = physiological process that occurs
when information is encountered
 Perception = psychological processes involved
in the immediate organization and interpretation
of sensations (influenced by our previous
knowledge, expectations, and biases)
 Attention = processes devoted to the monitoring
of internal and external events, information,
objects, etc.
Sensations
 Physiological reaction to encountering information (system is
stimulated)
 Processes in which physical energy from the environment is
transduced into neural responses that represent basic information
about the stimulation received by the sensory receptors.
 Sensory systems respond consistently; our experiences (our
perceptions) are different most of the time
 Sensory information and “tools”
 Visual system = light waves; fovea, receptive field, receptors (rods
and cones), ganglion and bipolar cells
 Auditory system = sound waves, frequency and intensity; pinna,
tympanic membrane, bones of the middle ear, cochlea, hair cell
receptors
 Olfaction = odor molecules, hair cell receptors
 Gustation = chemicals, papillae, taste buds
 All systems have neural components that take the sensory
“messages” to the brain
Perception
 Registering information/stimuli and apply prior
knowledge and experience to interpretation of that
information
 Processing of this information can happen in two
ways:


Bottom-up or Data-Driven Processing = flow of
information from the stimulus to the brain (neural
activity), to interpretation or identification
Top-Down or Conceptually-Driven Processing =
processing starts with previous knowledge influencing
what we see, hear, touch, taste, smell
Perception and Psychophysics
 Reminder: Psychophysics involves studying the
relationship between the physical aspects of the stimulus
and how the stimulus is perceived
 Thresholds – way of describing stimulus energy and how
it impacts the detection of the stimulus


Absolute Threshold – amount of stimulus energy needed to
detect the stimulus 50% of the time
Difference Threshold – amount of change in stimulus
energy that is detectable 50% of the time
 Sensitivity – knowledge that a stimulus was
perceived/detected
 Response Bias – willingness to report that a stimulus was
perceived/detected
 Signal Detection Theory – both sensitivity and response
bias characterize your perceptual experiences
The Box – Signal Detection Theory
The Stimulus is…
Your
decision –
You say
the
stimulus
is…
Present
Present
Absent
Hit
False Alarm
Miss
Correct Rejection
(liberal)
Absent
(conservative)
Cool Aspects of Perception
 Harold and the Purple
Crayon
 http://www.hbofamily.co
m/programs/jam/harold.
html
More Cool Aspects
 McGurk Effect – visual influence on speech
perception


Hear one syllable (ba) and see an image of
someone pronouncing another syllable (ga)
When these are different, the sound hear is a
combination of the two syllables (ba–da--ga)
 Synethesia – input to one sensory system
stimulates a reaction from another sensory
system (e.g., pitch and color)
 Subliminal Perception or Perception without
Awareness
(PAY) Attention
 Voluntary Control – we are in control of how
we deal with incoming information
 Limited Capacity – we cannot effectively
attend to (monitor) all events occurring
around us at the same time
 Selective Attention
 Divided Attention
Theories of Attention
 Gateway Theories – attention is a filter
 Dichotic listening tasks and speech shadowing
 Early Selection Theories


Filter Model of Attention (Broadbent, 1958)
Opposing evidence


Cocktail Party Phenomenon
Treisman (1960) – perception vs. meaning
 Attenuation Theory (Treisman, 1960)
 Late Selection Theories
Gateway Theories of Attention
 Early Selection
 Message 1 (attended)
x
Sensory
Memory
Meaningful
processing
Response
Meaningful
processing
Response
x
 Message 2 (unattended)
 Attenuation
 Message 1 (attended)
Sensory
Memory
 Message 2 (unattended)
 Late Selection
x
 Message 1 (attended)
Sensory
Memory
Meaningful
processing
Response
x
 Message 2 (unattended)
Early
Late
Attention as Capacity
 Attention is limited and must be allocated
according to the demands of the situation
 This is the idea of attentional “resources”
 Is there one resource type; are there multiple
types (perhaps based on modality)?
 Issue regarding capacity – can we overload
our attentional system? (i.e., run out of
attentional resources)
Multimode Theory of Attention
 Attention is flexible in
that people can shift
from early modes of
attention (processing
physical characteristics
of stimuli) to late modes
(processing meaning)
 Johnston and Heinz
(1978)
Response
Time
180
160
140
120
100
80
60
40
20
0
One List
Male/Female
Lists
Meaningful
Lists
Type of List
Automaticity
 Automatic Processing = some activities
require very little attention; usually the result
of practice.
 Examples: Stroop Effect and Visual Search
Studies
 Action slips = behaving in the absence of
attention
Putting it all together
Perception
Information