1. Sensation and Perception

2. Sensation

3. Can you read the following?
.rat eht saw tac ehT
tHeBOyrAnfAst.

4. Sensation
Stimulus- any aspect of or change in the environment to which an organism responds
Sensation- what occurs when a stimulus activates a receptor
Perception- the organization of sensory information into meaningful experiences

5. Processing
Bottom-Up Processing- analysis that begins with the sense receptors and works up to the brain’s integration of sensory information
Top-Down Processing- information processing guided by higher-level mental processes
as when we construct perceptions drawing on our experience and expectations

6. Threshold
Laws of sensation are found by figuring out how much of a stimulus is necessary for a person to sense it
Absolute threshold- the weakest amount of a stimulus that a person can detect half the time
Our senses: vision (candle flame= 30 miles); hearing (watch ticking 20 feet); taste (1 tsp of sugar in 2 gallons of water); smell (1 drop of perfume in 3 room house); touch (bee’s wing falling a distance of 1 cm onto your cheek)
Humans are limited

7. Thresholds 25 50 75 100 Low Absolute threshold Medium25 50 75
100
Low
Absolute
threshold
Medium
Intensity of stimulus
Percentage
of correct
detections
Subliminal
stimuli
Thresholds

8. Sensory Differences and Ratios
Difference threshold- the smallest change in a physical stimulus that can be detected half the time
Depends more on change than the absolute size
Weber’s law- the larger or stronger a stimulus, the larger the change required for a person to notice that anything has happened to it
Some people are more sensitive to these changes

9. Sensory Adaptation
Senses are most responsive to change, instead of constants
Our senses “get used” to stimuli

10. Signal- Detection Theory
= the study of people’s tendencies to make correct judgments in detecting the presence of stimuli
No single absolute threshold for a stimulus
Depending on ability to block other stimuli, affects ability to sense stimulus

11. The Senses

12. Senses Five main senses: vision, hearing, taste, smell, and touch
Also skin senses
Two internal senses
Vestibular- regulates sense of balance
Kinesthetic- sense of movement and body position

13. Vision
Light enters the pupil (opening in the iris that regulates the amount of light entering the eye)
Reaches the lens (flexible structure that changes its shape to focus light on the retina (innermost coating of the back of the eye, containing the light-sensitive receptor cells- rods and cones)
Rods and cones change light into neuronal impulses to send along the optic nerve (nerve that carries impulses from the retina to the brain’s occipital lobe

14. Vision continued

15. Vision continued
Blind spot= point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there
Psychological factors for pupil size
Disgusted= smaller
Like something= larger
Afraid= open wide

16. Vision continued Light- form of electromagnetic radiation
Objects absorb and reflect light
Color Deficiency- hereditary
When a person’s cones do not function properly
Most see some colors

18. Vision continued
Binocular fusion- the process of combining the images received from the two eyes into a single, fused image
Retinal disparity- the differences between the images stimulating each eye
Nearsightedness (eyeball is too long) vs. farsightedness (eyeball is too short)

19. Hearing
Vibrations of the air (sound waves) pass through bones to reach inner ear with hairlike cells
Hair cells change vibrations into neuronal signals that travel through auditory nerve to the brain

20. Hearing continued
Loudness is from heigh of sound waves measured in decibels (0-140)
damages hearing
Pitch depends on frequency of waves
Deafness- conduction (hearing aids) vs. sensorineural (cochlear implant)

22. Smell and Taste (chemical senses)
Gaseous molecules enter your nose in vapors to reach membrane in nasal passages with receptors that send messages through olfactory nerve
Taste
Liquid chemicals stimulate receptors on taste buds
Four experiences- sour, salty, bitter, sweet
Most of taste is produced by sense of smell
Also by warmth, cold, and pressure

23. Skin Senses (touch) Receptors tell: pressure, warmth, cold, and pain
Sensitivity varies based on amount of receptors
Some are sensitive to hot or cold stimuli

24. Skin Senses (touch): Pain
Functions as emergency system
Relies on many stimuli
Gate control theory- we can lesson some pains by shifting our attention away from the pain impulses or by sending other signals to compete with the pain signals

25. Perception

26. Components
Translating a physical stimulus into the language of the nervous system (neural impulses)
Comprehending the basic components of the stimulus, such as shape, size and color
Organizing the components into an understandable explanation

27. Gestalt
=the experience that comes from organizing bits and piece of information into meaningful wholes
Principles- proximity, continuity, similarity, simplicity, closure

29. Gestalt continued
Figure-ground perception- perceptual organization that is the ability to discriminate between a figure and its background
Perceptual inference- filling in the gaps if what our senses tell us
Example- seat is solid

30. Learning to Perceive We learn to perceive
Size of a human face...actual face
Active involvement in environment is important for accuracy
Influenced by our needs, beliefs, and expectations
Subliminal messages- brief auditory or visual messages that are presented below the aboslute threshold
Concerns about subliminal advertising

31. Depth Perception
=ability to recognize distances and three-dimensionality, develops in infancy
Monocular depth cues- cues that can be used with a single-eye
Relative height, interposition, light and shadows, texture-density gradient, linear perspective, relative motion
Motion parallax- the apparent movement of stationary objects relative to one another that occurs when the observer changes position
Binocular depth cues-depends on both eyes
Convergence, retinal disparity

32. Constancy and Illusions
Constancy- the tendency to perceive certain objects in the same way regardless of changing angle, distance, or lighting
Illusions- perceptions that misrepresent physical stimuli
Cues are distorted so that our brains cannot correctly interpret space ,size, and depth cues

35. ESP
=Extrasensory Perception, an ability to gain information by some means other than the ordinary senses
Clairvoyance, telepathy, psychokinesis, precognition

36. EXTRA TOPICS
The survival of many animals is dependent upon their senses. For example, deer have a heightened sense of smell that allows them to detect predators.
Research the sensory skills of one of the following and write a one-page summary on how the animal uses the sense as a primary means of survival.
Hearing in dogs, dolphins, or bats
Smell in lobsters, honeybees, or ants
Vision in predatory birds like hawks or owls

37. EXTRA TOPICS
Psychologists usually apply Weber’s law and sensory adaptation to one of the five senses, such as taste. Do you think the same concept can be applied to the effects of the media upon behavior? For example, does the prevalence of violence on television make people less shocked by violence in general? Or does the use of disrespectful language make people less courteous in their day-to-day lives/ find at least two magazine or newspaper articles on the subject and write summaries of the points made by the articles.

38. EXTRA TOPICS
Stroop Effect

39. EXTRA TOPICS
Our perception of ourselves is based, in large parge, on our mirror image, since this is the image we see most frequently. Lewis Carroll, the author of Alice in Wonderland, was fascinated by words that appeared the same when viewed in a mirror. Print the following words in block, capital letters: BEECH, COOKBOOK, BOX. hold the paper in the mirror.
Now turn the paper upside down.
Think of other words that would look the same when turned upside down and viewed in a mirror

40. EXTRA TOPICS
Research ESP and prepare a chart showing the different types of ESP experiences that you have uncovered. Present this chart and an overview of opinions on ESP.
Do you think parapsychology is a legitimate offshoot of psychology?

41. EXTRA TOPICS
Search the internet for information and examples of optical illusions. Present examples to the class and explain how the illusions were created.