This document summarizes key concepts related to sensation and perception. It discusses the five traditional senses of vision, hearing, touch, taste, and smell. It describes sensation as the detection of stimuli by sensory receptors and perception as how the brain interprets these sensations. Sensory thresholds and adaptation are explained. Factors that influence perception like beliefs, emotions, and context effects are also summarized.

1. Sensation and Perception

2. Sensation
• The process of detecting a stimulus (something that attracts
the attention of a sensory organ)
• the stimulation of sensory receptors and the transmission of
sensory information to the central nervous system
Five Traditional Senses:
• Vision
• Hearing
• Touch
• Taste
• Smell

3. Sensation Sensory Receptors: located
in the sensory organs
• cells that convert physical energy in the environment or
the body to electrical energy that can be transmitted as
nerve impulses to the brain
• Eyes
• Ears
• Nose
• Tongue
• Hands

4. Thresholds
• minimum amount of any given sensation that has to be
present for us to notice it
• E.g: Ticking of a watch from 20 ft away
Absolute Threshold:
• minimum amount of a stimulus that is necessary for us to
notice it 50% of the time
• 1 drop of perfume in a small house
Just Noticeable Difference: (Difference Threshold)
• Smallest amount of difference in amount of stimulation that a
specific sense can detect (difference in shades of two colors)
E.g: Smallest difference in the shades of red your eye can see

5. Cont..
Sense Absolute threshold
smell A drop of perfume diffused throughout a six-room
apartment
Taste One teaspoon of sugar in two gallons of water
Touch An insect’s wing falling on your cheek from a height of
about half an inch
Hearing The tick of a watch at 20 feet in a quiet room
sight A candle flame 30 miles away on a clear, dark night

6. Sensory Adaptation
• process by which we become less aware of weak stimuli
• if a stimulus is unchanging, we become desensitized to it
• We adapt to lying on a beach by becoming less aware of
weak stimuli like the sounds of the ocean
• We adapt to living near a highway by becoming less aware
of the sounds of traffic

7. Sensory Overload
• Can use selective attention to reduce sensory overload
• Selective Attention focusing of attention on selected
aspects of the environment and the blocking out of others

8. The Eye
• Cornea
Protects eye and bends light toward lens
• Lens
Focuses on objects by changing shape.
• Iris
Controls amount of light that gets into eye.
• Pupil
Widens or dilates to let in more light.

9. The Eye
• Retina
Neural tissue lining the back of the eyeball’s interior, which contains the
receptors for vision.
• Rods
Visual receptors that respond to dim light.
• Cones
Visual receptors involved in color vision. Most humans have 3 types of cones.

10. The Ear
• Loudness
The dimension of auditory experience related to the
intensity of a pressure wave.
• Pitch
The dimension of auditory experience related to the
frequency of a pressure wave.
• Timbre
The distinguishing quality of sound; the dimension of
auditory experience related to the complexity of the pressure
wave.

11. The Ear
• Auditory Localization:
Sounds from different directions are not identical as they
arrive at left and right ears
• Loudness
• Timing
• Phase
The brain calculates a sound’s location by using these
differences.

12. The Ear
• Three theories on how we perceive sound:
• Frequency Theory
Neural impulses are stimulated more with higher frequencies of air
waves
• More plausible for small frequencies, rather than high frequencies
because we can hear freqs higher than the maximum rate of neural
firing (1,000 neurons a second)
• Place Theory
Different frequencies of air waves activate different places along the
basilar membrane
• Volley Theory
Neurons fire out of sequence to add up to a certain Hz

13. Smell
• Olfaction Lock-and-key
• Detects molecules in the air
• Olfactory receptors (i.e., the locks) are built so that only
molecules (the keys) with particular shapes will fit in
particular receptors
• Receptors send neural signals to the brain, passing the
thalamus (memory) and the limbic system (emotions)
along the way
• This is why odors often trigger emotional memories

14. taste
Process
• Sense of taste combines with the sense of smell to produce perception of
flavor of food
• Research suggests that neural impulses for both senses converge to some
degree in brain area associated with the perception of flavor
• When the sense of smell is blocked, we have a harder time detecting most
flavors

15. Skin Senses Touch
• Skin is the body’s largest sensory organ
• Millions of skin receptors mix and match to produce
specific perception
• Four basic types of sensations
• Pressure
• Warmth
• cold
• pain

16. Skin Senses Temperature
• Two separate sensory systems – one for signaling warmth
and the other for signaling cold
• Also have distinct spots on the skin that register only
warmth or cold
• If you activate both at the same time, the person
perceives ‘hot’!

17. Skin Senses Pain
Pain serves a function
• it warns us of impending danger Endorphins
• Neurotransmitters in the brain that have a pain-killing
effect
Gate-control theory
• Pain impulses can be inhibited by closing of neural gates
in the spinal cord

18. Body Senses
Kinesthetic sense
• Provides info about position of joints, muscles, limbs
• Gives us control over body movements
Vestibular sense
• Provides info about body’s orientation relative to gravity
and head’s position in space
• Helps us maintain balance
• Relies on semicircular canals in the inner ear

19. Perception:
• process by which the brain organizes & interprets sensory
information
• uses sensory information to form a meaningful pattern
• final, organized, meaningful experience of sensory information
An example:
• Have you ever started the car and had to quickly turn down the
volume on the radio from where it was set last time you were in the
car?
• The level of energy (I.e., loudness) of the radio hasn’t changed
• (the volume know remains in the same place as when you last had it
on),
• but your perception of the loudness has changed drastically!

20. Influences on Perception
• Our needs affect our perception because we are more
likely to perceive something we need
• Our beliefs can affect what we perceive
• Emotions, such as fear, can influence perceptions of
sensory information
• All are influenced by our culture.
• Expectations based on our previous experiences influence
how we perceive the world.

21. Perceptual Set
• What you see in the centre figures depends on the order in which you look at
the figures:
• If you scan from the left, see an old woman
• If you scan from the right, see a woman’s figure

22. Context Effects
• The same physical stimulus can be interpreted differently
• We use other cues in the situation to resolve ambiguities
• Is this the letter B or the number 13?

23. Rules of Perceptual Organization
• Gestalt Principles of Vision:
• notes the various ways people make sense of sensory
information through:
• Figure-Ground
• The recognition of objects against a background
• What we perceive as the object & perceive as the
background influence our perception

24. Cont..

25. Rules of Perceptual Organization
Proximity
• Grouping together visual & auditory stimulus which are near
to one another
• Marks near one another tend to be grouped together
• What do you see?- 3 rows of dashes or 36 dashes
Similarity
• Tendency to group elements together that look alike
• Marks that look alike tend to be grouped together
• What do you see?- 3 columns of red or a 4 x 6 pattern

26. Rules of Perceptual Organization
Closure
• We tend to fill in gaps in what your senses tell you
Continuity
• Marks that tend to fall along a smooth curve or a straight
line tend to be grouped together
• People prefer to see smooth continuous
patterns not disrupting ones

27. Depth and Distance
Binocular Cues:
• Visual cues to depth or distance that require the use of both eyes.

28. Cont..
Convergence:
• Turning inward of the eyes, which
they focus on a nearby object.
Retinal Disparity:
• The slight difference in lateral
two objects as seen by the left eye
eye.

29. Depth and Distance
Monocular Cues
• visual cues to depth or distance that can be used by
one eye alone.
• Cues create the illusion of three dimensions or depth
on two-dimensional or flat surfaces
• Cause certain objects to appear more distant than
others

30. Visual Constancies
• The accurate perception of objects as stable or unchanged despite changes in
the sensory patterns they produce.
• Size constancy
• Color constancy
• Brightness constancy
• Shape constancy

31. Size Constancy
• the tendency to perceive an
object as being of one size no
matter how far away the object
is

32. Color Constancy
• the tendency to perceive an object
as keeping their color
• even though different light may
change the appearance of their color

33. Brightness Constancy
• the tendency to perceive an object as being equally bright
• even when the intensity of the light around it changes

34. Shape Constancy
• the knowledge that an item has only one shape
• no matter what angle you view it from
• even though these images cast shadows of different shapes, we still see the
quarter as round

35. Illusion or perceptual illusion
• The misperception of the true characteristics of an object or an
image.
• Illusory Contours: How Many Triangles Do You See?
• The Gestalt principles of perceptual organization contribute to
the illusion of triangular contours in this image.
• you instantly reverse figure and ground so that the black circular
regions become the ground,
• while the white region is visually favored as the figure.
• . The images produce a second intriguing illusion:
• The pure white illusory triangle seems brighter than the
surrounding white paper

37. The Müller-Lyer Illusion
• Compare the two photographs.
• Which corner line is longer?
• Now compare the two line drawings.
• Which center line is longer?
• In reality, the center lines in the photographs and the line drawings
are all exactly the same length
• which you can prove to yourself with a ruler

38. moon illusion
• A visual illusion involving the misperception
that the moon is larger when it is on the
horizon than when it is directly overhead.
The Moon Illusion Dispelled
• The moon illusion is subjectively very
compelling.
• When viewed on the horizon, the moon
appears to be much larger than when it is
viewed higher in the sky.
• But as this time-lapse sequence of the moon
rising over the Seattle skyline shows, the size
of the moon remains the same as it ascends
in the sky.

39. Extra Sensory Perception
• Extrasensory perception (ESP) is perception that occurs
independently of the main physical senses
• (sight, hearing, touch, taste and smell or, indeed, perceptual
processes such as proprioception)
• In some ways the term is vague but it is generally used to imply
a source of information that is unknown to modern science

40. Types
• Telepathy
• Clairvoyance
• Precognition and Retrocognition
• Experimental evidence
a) Restricted-choice experiments
b) Free-response experiments

41. Telepathy
• the source of information is another person’s mind
• The principle requirement of telepathic transmission is that the information transfer
cannot be explained by any known physical process
• Often the demonstration involves information transfer over large distances
• Unlike physical information transfer, telepathy is not subject to the weakening of the
signal the further you move away from the source
Clairvoyance
• we can propose clairaudience where the source of information is auditory rather than
visual
• Clairaudience is an alleged psychic ability to hear things that are beyond the range of
the ordinary power of hearing
• such as voices or messages from the dead
Precognition and retrocognition
• clairvoyance or clairaudience concerns things in the future or the past the these are
referred to as precognition and retrocognition respectively
• Dreams have sometimes been related to precognition
• Retrocognitions can be about recent events
• (e.g. the perpetrator of a recent murder) or distant events (e.g. historic events)
Retrocognition is different from past life regression

42. Experimental evidence
• experiments fall into two broad categories
• Restricted-choice experiments
• The receiver must make a decision about what is being transmitted from a
small set of known possibilities
Free-response experiments
• Here the sender will choose an item from a large but finite set of possible
stimuli
• The receiver is not told anything about the nature of the chosen stimulus
The remote viewing you participated in was a free-response set up.