Introduction to Psychology Sensation & Perception Pr BARAKAT Summer Session

1. Introduction to Psychology Sensation & Perception • Pr BARAKAT • Summer Session

2. Sensation: your window to the world Perception: interpreting what comes in your window.

3. Learning Outcomes • Define and differentiate between sensation and perception • Identify the parts of the eye, describe the properties of light and the theories of color vision • Describe how visual perception is organized • Identify the parts of the ear; explain the sense of hearing • Describe the kinesthetic and vestibular senses • Explain why psychologists are skeptical about extra sensory perception

4. What are Sensation and Perception? • The stimulation of sensory receptors and transmission of sensory information to the central nervous system • The process by which sensations are organized and interpreted to form an inner representation of the world • E.g., Recognizing people from their hair, etc., but not face

5. Absolute Threshold • Weakest amount of a stimulus that can be distinguished from no stimulus at all • Detected 50% of the time

6. 2. Absolute Threshold • Weakest amount of a stimulus that can be distinguished from no stimulus at all • Detected 50% of the time

7. Difference Threshold • Minimum difference in magnitude of two stimuli required to tell them apart • Detected 50% of the time • Standard of difference - Light – 2% of intensity - Weight – 2% of weight - Sound – one-third of 1% change in pitch (frequency) -Taste – 20% difference in saltiness

8. Influences on Perception • Stimulus characteristics and psychological factors interact to influence whether a stimulus is detected • Psychological factors such as learning, motivation, and psychological states (attention) • Perceptual set- what we expect to perceive • Attention (Inattentional blindness) • Social perception

9. Transduction & Adaptation Transduction Adaptation After a time, the sensory receptors grow accustomed to constant, unchanging levels of stimulus-sights, smell, etc. Therefore, we notice it less & less. • Sensory receptors- detect and respond to one type of sensory stimulus- light, smell, etc. • the sensory receptors convert the sensory stimulation into neural impulses.

10. Transduction • Transforming signals into neural impulses • Information goes from the senses to the thalamus , then to the various areas in the brain

11. Sensory Adaptation • Decreased responsiveness to stimuli due to constant stimulation. Do you feel your underwear all day?

12. Cocktail-party phenomenon • The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. • A form of selective attention.

13. Energy Vs. Chemical senses Energy Senses Chemical Senses

14. Vision • Our most dominating sense. • Visual Capture

15. Vision & Light • Spectrum of electromagnetic energy • Vary in wavelength • Human eyes can perceive only a very thin band of electromagnetic waves, known as the visible spectrum (400 – 700 nanometers) • Within visible light, color is determined by wavelength

16. The Visible Spectrum

17. Phase One: Gathering Light • The height of a wave gives us it’s intensity (brightness). • The length of the wave gives us it’s hue (color). • The longer the wave the more red. • The shorter the wavelength the more violet.

18. Phase II: Getting the light in the eye

19. Phase III: Transduction

20. Transduction (Cont.) • Order is Rods/Cones to Bipolar to Ganglion to Optic Nerve. • Sends info to thalamus- area called lateral geniculate nucleus (LGN). • Then sent to cerebral cortexes. • Where the optic nerves cross is called the optic chiasm.

21. Phase Four: In the Brain • Goes to the Visual Cortex located in the Occipital Lobe of the Cerebral Cortex • Feature Detectors • Parallel Processing We have specific cells that see the lines, motion, curves and other features of this turkey. These cells are called feature detectors.

22. Color Vision Two Major Theories

23. Trichromatic Theory Three types of cones: • Red • Blue • Green • These three types of cones can make millions of combinations of colors. • Does not explain afterimages or color blindness well.

24. Opponent-Process theory The sensory receptors come in pairs. • Red/Green • Yellow/Blue • Black/White • If one color is stimulated, the other is inhibited.

25. Afterimages

26. Perceptual Dimensions of Color • Afterimage • Persistent sensation of color are followed by perception of the complementary color when the first color is removed • Colour-Blindedness • Trichromat • Normal color vision • Monochromat • Totally color blind • Dichromat • Partial color blindness • Discriminate between two colors (red & green, or blue & yellow) • More common in males (sex-linked trait)

27. Visual Perception • Process used to organize sensory impressions caused by the light that strikes our eyes • Sensation is a mechanical process • Perception is an active process • Involves experience, expectations and motivations

28. End of the First Part

29. SECOND PART Perceptual Organization

30. 1. Visual Perception • Process used to organize sensory impressions caused by the light that strikes our eyes • Sensation is a mechanical process • Perception is an active process • Involves experience, expectations and motivations

31. Perceptual Organization (Cont.) Figure – Ground Perception Ambiguous, unstable figures, we shift back & forth

32. Gestalt Rules for Perceptual Organization • Common Fate • Elements moving together are grouped together (runners) • Closure • Fit bits of information into familiar patterns; • Perception of a complete figure, even when there are gaps in sensory information • Proximity • Nearness of objects • Similarity • Similarity of objects • Continuity (Series of points having unity)

33. Hearing Our auditory sense

34. We hear sound WAVES • The height of the wave gives us the amplitude of the sound. • The frequency of the wave gives us the pitch of the sound.

35. The Ear

36. Transduction in the ear • Sound waves hit the eardrum then anvil then stirrup then oval window. • Everything is just vibration. • Then the cochlea vibrates. • The cochlea is lined with mucus called basilar membrane. • In basilar membrane, there are hair cells. • When hair cells vibrate they turn vibrations into neural impulses which are called organ of Corti. • Message Sent then to thalamus up auditory nerve. It is all about the vibrations!!!

37. Pitch Theories Place Theory and Frequency Theory

38. Place Theory • Different hairs vibrate in the cochlea when they receive different pitches. • So some hairs vibrate when they hear high and other vibrate when they hear low pitches.

39. Frequency Theory • All the hairs vibrate but at different speeds.

40. Deafness Conduction Deafness Nerve (sensorineural) Deafness The hair cells in the cochlea get damaged. Loud noises can cause this type of deafness. NO WAY to replace the hairs. Cochlea implant is possible. • Something goes wrong with the sound and the vibration on the way to the cochlea. • You can replace the bones or geta hearing aid to help.

41. The Skin SensesTouch & Pressure • Sensory receptors in skin fire when skin surface is touched • Active touching • Some areas of the body are more sensitive • Nerve endings are more densely packed • More sensory cortex is devoted to perception of sensations

42. Touch & Pressure (Cont.) • Receptors located in our skin. • Gate Control Theory of Pain

43. Temperature • Receptors are located just beneath the skin • Skin temperature increases – receptors for warmth fire • Skin temperature decreases – receptors for cold fire • Sensations for temperature are relative

44. Pain • Receptors in skin are stimulated • Pain is usually sharpest where nerve endings are densely packed • Pain can be felt deep within body • No nerve endings for pain in the brain

45. Pain (Cont.) • Prostaglandins • Facilitate transmission of pain message • Heighten circulation to injured area (inflammation) • Pain-relieving drugs inhibit production of prostaglandins • Emotional response and response to stress affect degree of pain

46. Example (Phantom Limb Pain) • 2 out of 3 combat veterans with amputated limbs report phantom limb pain • May involve activation of nerves in the stump of missing limb • May also involve reorganization of motor and somatosensory cortex

47. Gate Theory of Pain • Nervous system can only process a limited amount of stimulation • Rubbing the pained area competes for neural attention • Closes the “gate” on pain messages to the brain

48. Acupuncture • Ancient Chinese method of pain control • Research shows it stimulates nerves to the hypothalamus releasing endorphins • Endorphins are similar in structure and effect to morphine

49. Taste • We have bumps on our tongue called papillae. • Taste buds are located on the papillae (they are actually all over the mouth). • Sweet, salty, sour and bitter.

50. Vestibular Sense • Tells us where our body is oriented in space. • Our sense of balance. • Located in our semicircular canals in our ears.