Sensation

1
Sensation PerceptionDay 1
2
Scientific Names for the Seven Senses (You
Should Know These)

• Seeing Visual
• Hearing Auditory
• Tasting Gustatory
• Smelling Olfactory
• Sense of Touch Tactile
• Balance Vestibular
• Body Sense Kinesthetic

3

• Sensation
• Information coming into our brain from our
  sensory receivers
• Perception
• The way the brain organizes and interprets the
  data received by our senses

Can you have sensation without perception?
Prosopagnosia Complete sensation in the absence
of perception
4

• Selective Attention the idea that we are only
  aware of a small percentage of what we experience

5
Selective Attention

• The most famous example to illustrate selective
  attention is known as the cocktail party effect.

6
Selective Attention

• Inattentional Blindness
• Failing to see something because our attention is
  elsewhere

• Change Blindness
• Failing to notice changes in the environment

7
Bottom-up Processing

• Analysis of the stimulus begins with the sense
  receptors and works up to the level of the brain
  and mind.

Letter A is really a black blotch broken down
into features by the brain that we perceive as an
A.
8
Top-Down Processing

• Information processing guided by higher-level
  mental processes as we construct perceptions,
  drawing on our experience and expectations.
• Top Down Processing explains how our expectations
  and prior experiences guide our perceptions.

THE CHT
9
Bottom Up Vs. Top Down

• What do you see?

10
Bottom Up vs. Top DownWhat do You See?
Optical Illusion Girlfriend
11
Psychophysics

• Psychophysics study of the relationship between
  physical characteristics of stimuli and our
  psychological experience of them
• Light - brightness
• Sound - volume
• Pressure - weight
• Taste - sweetness

12
Thresholds

• Absolute Threshold
• Minimum stimulation needed to detect a particular
  stimulus 50 of the time.

Subliminal Messages Messages presented below
absolute thresholds not consciously perceived
13
Subliminal Messages

• Some have argued that humans still pick up
  these messages that influence our unconscious.
  Do these messages have suggestive powers?
• Skeptics argue Subliminal Messages are heavily
  influenced by top down processes.
• Example Feeling hungry during subliminal
  advertisements.

14
Subliminal Messages

• What does the research say?

15
Difference Threshold Amount of change needed to
notice that a change has occurred.
Webers Law The greater or stronger the
stimulus, the greater the change required to
notice that a change has occurred. The two
stimuli must differ by a constant minimum
percentage (rather than a constant amount), to be
perceived as different. JND just noticeable
difference
16
Sensation Thresholds

• Signal Detection Theory predicts how and when we
  detect the presence of a faint stimulus (signal)
  amid background stimulation (noise)
• Assumes that there is no single absolute
  threshold because the idea of a threshold ignores
  the decision-making ability of the test subject.
• What might a persons detection of a stimulus
  depend on?

17
Signal Detection Theory

• There are four possible stimulus/response
• Hit Stimulus is presented and observer responds
  Yes
• Miss Stimulus is presented and observer responds
  No
• False alarm Stimulus is not presented and
  observer responds Yes
• Correct rejection Stimulus is not presented and
  observer responds No

18
Sensory Adaptation

• Diminished sensitivity as a consequence of
  constant stimulation.

Put a band aid on your arm and after awhile you
dont sense it.
19
Now you see, now you dont
20
The EYE vision
21
David HUBEL Torsten WIESEL
key name

• Discovered that most cells in the visual cortex
  only respond to particular features. For example,
  maybe a cell responds only to lines at this \
  angle.

Wiesel was awarded the 1981 Nobel prize in
Medicine and Physiology. His Nobel Lecture was
entitled 'The postnatal development of the visual
cortex and influence of environment. Wiesel
recognized that covering one eye of a young
animal could cause that eye to lose its
connection to the visual cortex.
22
Feature Detection
Nerve cells in the visual cortex respond to
specific features, such as edges, angles, and
movement.
Ross Kinnaird/ Allsport/ Getty Images
23
The Eye
24
Biology of Vision Know the Steps

1. Light enters the eye through the cornea
   (transparent protector) and passes through the
   pupil (small opening/hole).
2. The size of the opening (pupil) is regulated by
   the iris the colored portion of your eye that
   is a muscular tissue which widens or constricts
   the pupil causing either more or less light to
   get in.

25
(No Transcript)
26
Biology of Vision Know the Steps

1. Behind the pupil, the lens, a transparent
   structure, changes its curvature in a process
   called accommodation, and focuses the light rays
   into an image on the light-sensitive back surface
   called the retina where image is focused.

27
Biology of Vision Know the Steps

1. Image coming through activates photoreceptors in
   the retina called rods and cones (process
   information for darkness and color).
2. As rods and cones set off chemical reactions they
   form a synapse with bipolar cells which
   transducts light energy into neural impulses.
3. The action potential travels along the ganglion
   cells which send information up the optic nerve
   (bundle of neurons that take information from
   retina to the brain)

28
Biology of Vision Know the Steps

• The Optic Nerve carries neural information to be
  processed by the Thalamus (sensory switchboard).
• Thalamus sends information to the visual cortex
  which resides in the occipital lobe.
• The brain then constructs what you are seeing and
  turns image right side up.

29
Parts of Retina

• Fovea central focal point of the retina, where
  cones cluster.
• Cones photoreceptor located near center of
  retina (fovea)
• fine detail and color vision
• daylight or well-lit conditions
• Rods photoreceptor located near peripheral
  retina
• detect black, white and gray
• twilight or low light
• Bipolar Cells create visual neural impulses

30
Most Common Errors In Vision

• Acuity the sharpness of vision
• Nearsightedness
• nearby objects seen more clearly
• lens focuses image of distant objects in front of
  retina
• Farsightedness
• faraway objects seen more clearly
• lens focuses near objects behind retina

31
(No Transcript)
32
(No Transcript)
33
COLOR vision
34
Physical Characteristics of Light

• Wavelength

• hue/color

Different wavelengths of light result in
different colors.
Green
Violet
Indigo
Blue
Yellow
Orange
Red
400 nm
700 nm
Long wavelengths
Short wavelengths
35
Amplitude
intensity/brightness
36
COLOR mixing

• Subtractive Color Mixing
• mixing pigments (like paint). Result is

Additive Color Mixing mixing different colored
lights. Result is
37
Retina

• Retina The light-sensitive inner surface of the
  eye, containing receptor rods and cones in
  addition to layers of other neurons (bipolar,
  ganglion cells) that process visual information.

38
Photoreceptors
Lets do a little experiment to map our rods
cones
E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969
39
Thomas YOUNG Hermann HELMOLTZ
key name

• Trichromatic color theory (RGB) - some cones are
  especially sensitive to red, some to green, some
  to blue

40
Typical cases of Color Blindness support the
Trichromatic theory.
41
Opponent Process Theory There are three opponent
channels red vs. greenblue vs. yellow black
vs.white
While the trichromatic theory defines the way the
retina of the eye allows the visual system to
detect color with three types of cones, the
opponent process theory accounts for mechanisms
that receive and process information from cones.
42
Opponent Process Theory
Gaze at the middle of the flag. When it
disappears, stare at the dot and report whether
or not you see Britain's flag.
What just happened is called a NEGATIVE AFTERIMAGE