1. Sensation and perception
Fatmah Sakran

2. Definitions Sensation:
The detection of physical energy emitted or reflected by physical objects
Occurs when energy in the external environment or the body stimulates receptors in the sense organs.
perception:
The process by which the brain organizes and interprets sensory information.

3. Stimulation Becomes Perception

4. Principles of sensation
Transduction -
Physical energy to neural signal
Sensory receptors – Specialized neurons that are activated by stimulation and transduce (convert) the incoming stimulus into electrochemical signals

5. Sensory pathway – Bundles of neurons that carry information from the sense organs to the brain
Sensory Adaption - refers to the fact that repeated or constant stimulation decreases the number of sensory messages sent to the brain, which causes decreased sensation.

6. Thresholds
Absolute threshold:- smallest strength of a stimulus tat can be detected
Difference threshold :- (jnd) smallest difference that can be detected

7. Thresholds Weber’s law –
The size of the JND is proportional to the intensity of the stimulus
The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low

8. Determining which stimuli will actually become sensation .
what the quality and impact of that sensation will be . and whether it grabs our interest

9. Comparison with personal standard
Signal Detection Theory
Signal detection theory – Perceptual judgment as combination of sensation and decision-making processes
Stimulus event
Neural activity
Comparison with personal standard
Action (or no action)

10. How Are the Senses Alike? How Are They Different?
- The senses all operate in much the same way, but each extracts different information and sends it to its own specialized processing region in the brain

11. vision purpose of the visual system
Transform light energy into an electrochemical neural response
Represent characteristics of objects in our environment such as size, color, shape, and location.

12. Anatomy of Visual Sensation

13. Distribution of Rods and Cones
Consentrated in peiphery
Approx. 120 million
Cones :-
concentrated in center of eye (fovea).
approx. 6 million
Blind spot:-
Point where the optic nerve exits the eye and where there are no photoreceptors.
region with no rods or cones

14. Differences Between Rods and Cones
Allow us to see in bright light
Allow us to see fine spatial detail
Allow us to see different colors
Rods
Allow us to see in dim light
Can not see fine spatial detail
Can not see different colors

15. Rods
Cones

16. Retinal Photoreceptors
Light passes through the retinal layers to reach the photoreceptors at the inner retinal surface.
Photoreceptors and bipolar cells conduct potentials to the ganglion cells, which in turn initiate action potentials which are transmitted to the thalamus.

18. How the Visual System Creates Color and Brightness
Wavelength
Intensity (amplitude)
Color
Brightness

19. How the Visual System Creates Color
Electromagnetic spectrum – -Entire range of electromagnetic energy, ---includes radio waves, X-rays, microwaves, and visible light
Visible spectrum – -Tiny part of the electromagnetic spectrum that is visible to our eyes
(INSERT IMAGE OF SPECTRUM HERE)

20. How the Visual System Creates Color
Trichromatic theory-
Based on 3 cone receptors
Explains initial stages of color vision
Opponent-process theory–
Based on bipolar cells
Colors in complementary pairs
Explains afterimages

21. Afterimages
Afterimages – Sensations that linger after the stimulus is removed
In the following slide, fix your eyes on the dot in the center of the flag

22. Complementary Afterimages

24. How the Visual System Creates Color
Color blindness – Vision disorder that prevents an individual from discriminating certain colors

25. Vision Test of Color Deficiency

26. The Sound Stimulus

27. Hearing: If a Tree Falls in the Forest...
The Physics of Sound
Frequency – Number of cycles completed by a wave in a given amount of time
Low Frequency
High Frequency

28. Hearing: If a Tree Falls in the Forest...
The Physics of Sound
Amplitude – Physical strength of a wave
High Amplitude
Low Amplitude

29. Decibel levels of different sounds

30. Hearing The Human Ear
Audition
The sense of hearing

31. How We Hear Sound Waves
Cochlea

32. Psychological Qualities of Sounds
Pitch – Sensory characteristic of sound produced by the frequency of the sound wave
Loudness – Sensory characteristic of sound produced by the amplitude (intensity) of the sound wave
Timbre – Quality of a sound wave that derives from the wave’s complexity

33. Position and Movement
Vestibular sense – Sense of body orientation with respect to gravity
Receptors in semicircular canals
Kinesthetic sense – Sense of body position and movement of body parts relative to each other
Receptors in joints, muscles, and tendons

34. Smell Olfaction – Sense of smell
Olfactory bulbs – Brain sites of olfactory processing
Pheromones – Chemical signals released by organisms to communicate with other members of the species

35. Other Senses Olfactory System
Structures responsible for the sense of smell

36. Other Senses Taste Buds
Nets of taste-receptor cells
This is a photograph of tongue surface (top), magnified 75 times.
10,000 taste buds line the tongue and mouth.
Children have more taste buds than adults do.
There are four primary tastes: sweet, salty, sour, and bitter.

37. Taste

38. The Skin Senses
Protects against surface injury, holds in bodily fluid, and helps regulate body temperature
Touch
Warmth
Cold
Pain

39. Other Senses The Thermal Grill
Temperature
When a person grasps two braided water pipes – one with cold water running through it and one with warm water – the sensation is “burning hot” and painful.
There are two separate pathways for warmth and cold.

40. Other Senses Pain Gate-control Theory Psychological control
Theory that the spinal cord contains a neurological “gate”that blocks pain signals for the brain when flooded by competing signals.
Psychological control
Mind over sensation, distraction

41. Other Senses Coordination Kinesthetic System Vestibular System
Structures distributed throughout body that sense position and movement of body parts.
Vestibular System
The inner ear and brain structures that afford a sense of equilibrium.

42. Keeping the Signals Straight
Synesthesia
Rare condition in which stimulation in one sensory modality triggers sensations in another sensory modality.
Each sensory system designed to operate separately from the others.
Selective Adaptation
A decline in sensitivity to a stimulus as a result of constant exposure.

43. What is the Relationship Between Perception and Sensation?
Perception brings meaning to sensation, so perception produces an interpretation of the external world, not a perfect representation of it

44. Perception Perceptual Organization Perceptual Constancies
Depth and Dimension
Perceptual Set
The World of Illusions

45. Perceptual Organization Reversible Figures
Drawings that one can perceive in different ways by reversing figure and ground.
Gestalt Psychology
School of thought rooted in the idea that the whole is different from the sum of its parts.

46. Perceptual Organization Gestalt Laws of Grouping
Proximity
Seeing 3 pair of lines in A
Similarity
Seeing columns of orange and red dots in B
Continuity
Seeing lines that connect 1 to 2 and 3 to 4 in C
Closure
Seeing a horse in D

47. Perceptual Organization Identifying Objects
Geons (geometric icons) are simple 3D component shapes.
A limited number are stored in memory.
Geons are combined to identify essential contours of objects.

48. Perceptual Constancies
Size Constancy
The tendency to view an object as constant in size despite changes in the size of the retinal image.
Shape Constancy
The tendency to see an object as keeping its form despite changes in orientation.

49. Perceptual Constancies The Ames Room
A specially-built room that makes people seem to change size as they move around in it
The room is not a rectangle, as viewers assume it is.
A single peephole prevents using binocular depth cues.

50. Perceptual Constancies Shape Constancy
Even though these images cast shadows of different shapes, they still are seen as round.

51. Depth and Dimension Depth Perception Convergence Binocular Disparity
The use of visual cues to estimate depth and distance.
Convergence
A binocular cue involving the turning inward of the eyes as an object gets closer.
Binocular Disparity
A binocular cue whereby the closer an object is, the more different the image is in each retina.

52. Depth and Dimension Monocular Depth Cues
Distance cues that enable the perception of depth with one eye.
Relative Image Size
Texture Gradient
Linear Perspective
Interposition
Atmospheric Perspective
Relative Elevation
Familiarity

53. Depth and Dimension The Visual Cliff
Devised by Eleanor Gibson and Richard Walk to test depth perception in infants and animals.
Provides visual illusion of a cliff.
Caregiver stands across the gap.
Babies are not afraid until about the age they can crawl.

54. Perceptual Set
What is seen in the center figures depends on the order in which one looks at the figures:
If scanned from the left, a man’s face is seen.
If scanned from the right, a woman’s figure is seen.

55. Perceptual Set Context Effects
The same physical stimulus can be interpreted differently depending on perceptual set, e.g., context effects.
When is the middle character the letter B and when is it the number 13?

56. The World of Illusions The Müller-Lyer Illusion
Illusion in which the perceived length of a line is altered by the position of other lines that enclose it

57. The World of Illusions The Ponzo Illusion
Illusion in which the perceived line length is affected by linear perspective cues.
Side lines seem to converge
Top line seems farther away
But the retinal images of the red lines are equal.

58. Extrasensory Perception
The Case for ESP
The Case against ESP
The Continuing Controversy

59. The Case for ESP Extrasensory Perception (ESP)
The ability to perceive something without ordinary sensory information.
This has not been scientifically demonstrated.
Parapsychologists distinguish between three types of ESP:
Telepathy – Mind-to-mind communication
Clairvoyance – Perception of remote events
Precognition – Ability to see future events

60. The Case against ESP ESP Cards
J. B. Rhine conducted many experiments on ESP using stimuli such as these.
Rhine believed that his evidence supported the existence of ESP, but his findings were flawed..

61. The Continuing Controversy
The ganzfield procedure
Researchers disagree about the reliability of studies done to replicate the ganzfield test.

62. Thank you