•
Perception
Thresholds
threshold
(or
limen)‐‐the
point
when
a
psychological
and/or
physiological
effect
is
produced
• absolute
threshold‐‐the
least
amount
of
a
stimulus
needed
to
trigger
a
sensory
perception
(e.g.
a
candle
at
one
mile
away)
• difference
threshold
(or
just
noticeable
difference)‐‐the
least
amount
of
difference
between
two
stimuli
for
perception
to
occur
• Gustav
Fechner
elaborated
on
Ernst
Weber’s
work
to
create
Weber’s
Law
•
–
Weber’s
Law
states,
to
be
perceptibly
different,
two
stimuli
must
differ
by
a
constant
proportion,
not
a
constant
amount
of
the
original
stimulus
– this
is
related
to
difference
thresholds
David
Hubel
and
Torsten
Wiesel
are
best
known
for
feature
detection
theory
– the
visual
cortex
has
feature
detector
neurons
that
receive
information
from
individual
ganglion
cells
in
the
visual
field
and
respond
to
a
scene’s
specific
features
– feature
detection
cells
in
the
visual
cortex
pass
on
information
to
other
cortical
cells
that
respond
only
to
more
complex
patterns
– the
visual
cortex
has
feature
detectors
for
a
variety
of
images;
what
we
perceive
is
a
combination
of
these
features
•
our
brain
naturally
engage
in
parallel
processing—processing
many
things
at
once
•
the
visual
scene
is
divided
by
the
brain
into
sub‐dimensions—movement,
color,
depth,
form
•
visual
perception
requires
integrating
these
separate
pieces
–
the
process
of
facial
recognition
requires
the
combined
efforts
of
about
30%
of
the
cortex
–
interrupting
facial
recognition
with
magnetic
pulses
will
disrupt
this
process
and
people
are
unable
to
recognize
the
face
–
magnetic
pulses
do
not
work
with
object
recognition,
however
The
Eye
Diagram
p.
205
•
•
•
•
The
Eye
the
structures
of
the
eye
from
the
diagram
are
as
follows:
– lens:
focuses
the
image
onto
the
retina;
the
image
is
focused
upside‐down
on
the
retina
– pupil:
regulates
the
amount
of
light
entering
the
eye;
full
dark
adaptation
takes
about
30
minutes
and
light
adaptation
about
1
minute
– iris:
the
colored
part
of
the
eye
– cornea:
the
soft,
outer,
protective
covering
of
the
eye
– retina:
contains
photoreceptor
cells,
rods
(which
detect
brightness
contrasts)
and
cones
(which
detect
color)
– fovea:
an
area
of
the
retina
that
contains
all
cones
and
no
rods
– optic
nerve:
relays
visual
information
to
the
brain
– blind
spot:
where
the
optic
nerve
connects
to
the
back
of
the
eye
How
We
See
gathering
light
• light
reflected
off
objects
• color
is
collected
through
both
light
intensity
(brightness)
and
light
wavelength
(color)
within
the
eye
• reflected
light
enters
the
eye
through
the
cornea
and
pupil
• the
iris
muscles
regulate
the
pupil
to
open
or
close
• the
light
is
focused
by
the
lens
onto
the
retina
transduction
• transduction‐‐translating
incoming
stimuli
into
neural
signals
• rods
and
cones
fire
in
an
area
of
the
retina
• these
photoreceptor
cells
activate
the
next
layer
of
bipolar
cells
• these
bipolar
cells
activate
ganglion
cells
• axons
of
these
ganglion
cells
make
up
the
optic
nerve
• the
optic
nerve
sends
these
impulses
to
the
lateral
geniculate
nucleus
of
the
thalamus
• these
impulses
are
sent
to
the
visual
cortex
in
the
occipital
lobe
• feature
detectors
are
activated
to
determine
lines,
curves,
motion
and
other
features
of
the
object
Transduction
Diagram
p.
207
•
•
•
•
•
The
Visual
Cortex
information
travels
from
the
eyes
to
various
parts
of
the
brain:
– the
thalamus
– the
visual
cortex
of
the
occipital
lobe
Hubel
and
Wiesel
have
developed
the
feature
detection
theory‐‐there
are
certain
cells
in
the
visual
cortex
that
are
sensitive
to
certain
features
of
a
stimulus
they
determined
there
were
three
types
cells
in
the
visual
cortex:
– simple‐‐provide
information
about
the
position
and
boundaries
of
a
stimuli
– complex‐‐provide
advanced
information
about
position
such
as
movement
– hypercomplex‐‐provide
abstract
information
such
as
shape
or
size
Color
Perception
subtractive
color
mixtures
deal
primarily
with
mixing
pigments
(e.g.
blue
and
yellow
mixed
together
make
green)
additive
color
mixtures
deal
primarily
with
mixing
lights
(e.g.
combining
a
green
and
red
light
will
give
you
yellow)
•
•
•
•
•
•
•
•
•
•
•
•
there
are
two
main
theories
of
color
perception:
– trichromatic
(or
Young‐Helmholtz)
theory:
all
color
perception
derives
from
three
different
color
receptors
in
the
retina
(usually
red,
blue
and
green);
while
this
theory
can
physically
recreate
the
spectrum
of
colors,
much
like
your
TV
set
does,
it
cannot
explain
color
blindness
or
negative
afterimages
– opponent
process
theory:
three
sets
of
color
receptors
(blue‐yellow,
red‐green,
black‐white)
respond
to
determine
the
color
you
experience;
explains
both
color
blindness
(which
tends
to
be
either
blue‐yellow,
red‐green,
or
full
color
blindness)
and
negative
afterimages;
this
was
proposed
by
Ewald
Hering
– there
are
typically
three
types
of
color
blindness:
blue‐yellow,
red‐green
and
complete
color
blindness
Adaptation
and
Habituation
adaptation‐‐the
process
by
which
you
sensory
systems
adjust
to
changes
in
the
environment
(e.g.
light
and
dark
adaptation)
habituation‐‐the
process
by
which
you
“tune
out”
distracting
stimuli
in
your
environment
dishabituation‐‐the
process
by
which
you
suddenly
“tune
back
in”
to
new
stimuli
(such
as
someone
calling
your
name)
Signal
Detection
Theory
signal
detection
theory‐‐how
distractions
and
interference
effect
how
we
perceive
the
world
response
criteria
(or
receiver
operating
characteristics)‐‐the
combination
of
signal
detection
theory
and
motivational
aspects
critical
in
detecting
certain
stimuli
and
what
we
expect
to
perceive
false
positive‐‐perceiving
a
stimulus
that
is
actually
not
there
false
negative‐‐not
perceiving
a
stimulus
that
is
actually
there
Attention
selective
attention—consciously
attending
to
a
particular
stimulus
and
disregarding
other
stimuli
selective
inattention—being
inattentive
to
all
but
a
small
amount
of
stimuli;
being
blind
to
inconsequential
stimuli
inattentional
blindness—inability
to
notice
visual
stimuli
when
our
attention
is
drawn
elsewhere
change
blindness—inability
to
notice
changes
in
the
surrounding
environment
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Broadbent’s
filter
theory‐‐the
idea
that
we
can
selectively
attend
to
certain
stimuli
and
disregard
other
information
(e.g.
talking
to
your
friend
in
a
noisy
restaurant);
an
all‐or‐nothing
filter
the
cocktail
party
phenomenon‐‐adjusts
Broadbent’s
filter
theory
from
an
“all‐or‐nothing”
filter
to
one
that
includes
dishabituation
(e.g.
at
the
restaurant
with
your
friend,
if
someone
calls
your
name
you
will
no
longer
filter
out
that
stimuli)
selection
attention
has
been
tested
through
dichotic
listening
experiments
in
which
subjects
are
presented
with
two
competing
messages
simultaneously
and
are
asked
to
attend
to
only
one
of
the
messages;
they
are
usually
successful
in
this
task
Perception
Processes
bottom­up
processing
usually
involves
data;
it
is
our
ability
to
take
individual
components
of
a
stimulus
and
to
put
it
together
according
to
fixed
rules
into
a
whole
pattern
top­down
processing
usually
involves
concepts;
it
is
our
ability
to
see
a
whole
concept
and
then
break
it
down
into
its
component
parts
Perception:
2D
Objects
in
3D
superposition‐‐when
one
object
overlaps
another
object;
we
see
one
object
as
being
in
front,
one
in
back
relative
size‐‐an
object
is
expected
to
grow
smaller
on
the
retina
the
further
away
it
becomes
linear
perspective‐‐when
two
line
converge
on
the
horizon
to
indicate
depth
or
distance
Perception:
Constancy
constancy­­the
ability
to
maintain
a
consistent
perception
of
an
object
– size
constancy‐‐knowing
that
an
object
maintains
a
consistent
size
regardless
of
our
distance
from
it
– shape
constancy‐‐knowing
that
an
object
maintains
a
consistent
shape
regardless
of
the
angle
at
which
we
perceive
it
– brightness
constancy‐‐knowing
that
an
object
maintains
a
consistent
color
despite
changing
light
conditions
Perception:
Depth
Perception
texture
gradient‐‐objects
appear
sharp
and
textured
up
close
but
less
sharp
and
detailed
further
away
motion
parallax‐‐variations
in
motion
and
speed
(e.g.
in
a
car,
close
object
appear
to
whiz
by
but
distant
objects
appear
to
be
moving
slower)
retinal
disparity
(or
stereopsis)‐‐the
slight
difference
in
visual
information
taken
in
through
both
of
our
eyes
figure­ground­­the
ability
to
separate
on
object
or
figure
from
its
background
Perception:
Gestalt
Perception
proximity‐‐if
objects
are
close
to
each
other
they
are
perceived
as
being
together
similarity‐‐similar
objects
are
typically
grouped
together
continuation‐‐the
perception
of
continuous
patterns
that
flow
in
the
same
direction
and
in
the
same
manner
subjective
contours‐‐seeing
objects
or
images
as
outlined
by
their
contours
closure‐‐our
desire
to
see
objects
as
complete,
even
in
the
absence
of
actual
stimuli
law
of
pragnanz‐‐perception
will
always
be
as
simple,
regular
and
symmetrical
as
possible
Perception:
Motion
of
Light
real
motion­­this
involves
actually
moving
the
light
(e.g.
spotlights)
phi
phenomenon­­when
lights
are
flashed
in
different
locations
so
that
they
appear
to
be
moving
(e.g.
theater
marquees)
induced
motion‐‐when
it
appears
a
light
is
moving
but
actually
everything
around
the
light
is
moving
•
•
•
•
•
•
•
•
•
autokinetic
effect‐‐in
a
dark
room
a
point
of
light
appears
to
move
because
there
is
no
frame
of
reference
for
it
Perception:
Cultural
Effects
several
rules
that
were
once
though
innate
may
actually
be
learned
some
cultures
do
not
use
linear
perspective‐‐images
using
this
technique
are
not
seen
as
three
dimensional
how
someone
perceives
an
optical
illusion
depends
on
culture
carpentered
cultures
are
fooled
by
this
illusion,
non‐carpentered
cultures
are
not
because
they
do
not
use
right
angles
and
corners
Extrasensory
Perception
extrasensory
perception
is
one
form
of
paranormal
phenomena
the
three
most
testable
forms
of
ESP:
– telepathy—mind‐to‐mind
communication
– clairvoyance—perceiving
remote
events
– precognition—perceiving
future
events
also
included
in
psychokinesis
– mind
over
matter
most
skepticism
on
ESP
revolve
around
two
issues:
– to
believe
in
ESP
you
must
believe
the
brain
is
capable
of
perceiving
without
sensory
input
– ESP
phenomena
under
controlled
conditions
cannot
be
replicated
AP
Check
AP
students
in
psychology
should
be
able
to
do
the
following:
• Discuss
basic
principles
of
sensory
transduction,
including
absolute
threshold,
difference
threshold,
signal
detection,
and
sensory
adaptation.
• Describe
sensory
processes
(e.g.
hearing
(pp.
217­220),
vision,
touch
(pp.
224­225),
taste
(pp.
229­
231),
smell
(pp.
231­233),
vestibular
(p.
234),
kinesthesis
(pp.
233­234),
pain
(pp.
227­229)),
including
the
specific
nature
of
energy
transduction,
relevant
anatomical
structures,
and
specialized
pathways
in
the
brain
for
each
of
the
senses.
• Explain
common
sensory
disorders
(e.g.
visual
and
hearing
impairments
(pp.
220­223)).
• Describe
general
principles
of
organizing
and
integrating
sensation
to
promote
stable
awareness
of
the
external
world
(e.g.
Gestalt
principles,
depth
perception).
• Discuss
how
experience
and
culture
can
influence
perceptual
processes
(e.g.
perceptual
set
(pp.
257­
259),
context
effects
(pp.
260­261)).
• Explain
the
role
of
top­down
processing
in
producing
vulnerability
to
illusion.
• Discuss
the
role
of
attention
(pp.
237­239)
in
behavior.
• Challenge
common
beliefs
in
parapsychological
phenomena
(pp.
266­268).