1. Sensation and Perception

2. Sensation
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
(eyes, ears, nose, tongue, hands)
Definition
cells that convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain

4. Sensation Five Sensory Receptors: Temperature Pressure Pain Balance
Motion

5. Perception Perception:
process by which the brain organizes & interprets sensory
information
using 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!

6. The Process

7. Thresholds Definition:
minimum amount of any given sensation that has to be present for us to notice it
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)
Smallest difference in the shades of red your eye can see

8. Sensory Adaptation 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

9. Sensory Overload Definition: Overstimulation of the senses.
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

10. “Our Visible Spectrum”
Light
“Our Visible Spectrum”
Red Orange Yellow Green Blue Indigo Violet
Hue determines color
Depends on length of the distance from one peak to the next on the wave
Brightness
Lightness and luminance; the visual experience related to the amount of light emitted from or reflected by an object.
Saturation
Vividness or purity of color; the visual experience related to the complexity of light waves.

11. 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.

12. 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.

13. The Ear Loudness Pitch Timbre
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.

14. The Ear

15. 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.

16. 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

17. 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

18. Taste Detects molecules of substances that have dissolved in saliva
Taste Buds
Clusters of hair-like receptor cells
Within each bud is a cluster of 50 to 150 receptor cells
We have about 10,000 (most on tongue)
Four types: sweet, sour, salty & bitter

19. taste
The 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

20. 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, and pain

21. 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’!

22. 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

23. Sensitivity to touch

24. Body Senses Kinesthetic sense Vestibular 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

25. 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.

26. 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

27. 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?

28. 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

29. 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

30. 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

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

32. Depth and Distance
Convergence: Turning inward of the eyes, which occurs when they focus on a nearby object.
Retinal Disparity: The slight difference in lateral separation between two objects as seen by the left eye and the right eye.

33. 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

34. 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

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

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

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

38. 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

39. Visual Illusions
Illusions are valuable in understanding perception because they are systematic errors that reveal our experiences
Illusions provide hints about perceptual strategies.
In the Ponzo Illusion (above) side lines seem to converge and top line seems farther away, but the retinal images of the red lines are equal!
In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left.