Sensation and Perception

1. Unit Three:Cognition, Sensation, Perception, and States of ConsciousnessAdapted from: Prentice Hall Psychology Publishingandwww.authorstream.com/Presentation/hedaoorahul-749339-dreams-pptCachedand

2. Sensation and Perception • Sensation: The detection of physical energy emitted or reflected by physical objects; it 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. Ambiguous Figure • Colored surface can be either the outside front surface or the inside back surface • Cannot simultaneously be both • Brain can interpret the ambiguous cues two different ways

4. Ambiguous Pictures

5. The Riddle of Separate Sensations • Sense Receptors: Specialized neurons that convert physical energy from the environment or the body into electrical energy that can be transmitted as nerve impulses to the brain. • Doctrine of Specific Nerve Energies: Different sensory modalities exist because signals received by the sense organs stimulate different nerve pathways leading to different areas of the brain.

6. Measuring the Senses • Absolute Threshold • The smallest quantity of physical energy that can be reliably detected by an observer • Difference Threshold • The smallest difference in stimulation that can be reliably detected by an observer when two stimuli are compared; also called Just Noticeable Difference (JND).

7. Sensory Adaptations • Sensory Adaptation: The reduction or disappearance of sensory responsiveness that occurs when stimulation is unchanging or repetitious. • Sensory Deprivation: The absence of normal levels of sensory stimulation.

8. Sensory Overload • Selective Attention: The focusing of attention on selected aspects of the environment and the blocking out of others.

9. An Eye on the World • 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. • Dark Adaptation: The process by which visual receptors become maximally sensitive to light.

10. Structures of the Human Eye

11. Structures of the Retina

12. The Visual System is Not a Camera • Much visual processing is done in the brain. • Some cortical cells respond to lines in specific orientations (e.g. horizontal) • Other cells in the cortex respond to other shapes (e.g., bulls-eyes, spirals, faces) • Feature-detectors: Cells in the visual cortex that are sensitive to specific features of the environment.

13. How We See Colors • Trichromatic Theory • Opponent Process Theory

14. Trichromatic Theory • T. Young (1802) & H. von Helmholtz (1852) both proposed that the eye detects 3 primary colors • red, blue, & green • All other colors can be derived by combining these three

15. VS VS VS Opponent-Process Theory • A competing theory of color vision, which assumes that the visual system treats pairs of colors as opposing or antagonistic. • Opponent-Process cells are inhibited by a color, and have a burst of activity when it is removed.

16. Optical Tricks • http://www.echalk.co.uk/amusements/OpticalIllusions/illusions.htm

17. How Culture Influences What We Perceive

18. Perceptual Set • Perceptual Set refers to perceptual expectations that make particular interpretations likely to occur and that increase both speed and efficiency of the perceptual process • Influenced by personal experience including deprivation e.g., Dawson (1975) and coin size for wealthy and deprived children; Environmental conditions and noise Pollack (1963); kittens in cylinders Blakemore & Cooper (1970) • Stress can influence perception and

19. Depiction perceptions are impacted by education; limited education results in misperception of posters (Hudson, 1960) • People scan pictures differently based on reading and writing patterns e.g., Hebrew and English speakers use left-to-right strokes for writing and scan the same way; Arab speakers use right-to-left direction for writing and scan the same way • Scanning may also be impacted by drawing i.e., directions of drawing circles

20. Depth Perception • The organization of sensations in three dimensions • Perceiving three dimensional images is confusing for those from extreme poverty and without formal schooling; Education and training can change this (Leach, 1975; Nicholson et al., 1977)

21. Depth and Distance Perception • Binocular Cues: Visual cues to depth or distance that require the use of both eyes. • 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. • Monocular Cues: Visual cues to depth or distance that can be used by one eye alone.

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

23. Visual Illusions • Illusions are valuable in understanding perception because they are systematic errors. • Illusions provide hints about perceptual strategies • In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left.

24. Fooling the Eye • The cats in (a) are the same size • The diagonal lines in (b) are parallel • You can create a “floating fingertip frankfurter” by holding hands as shown, 5-10” in front of face.

25. Are People Equally Misled by Visual Illusions? • Non-Western and rural participants showed less susceptibility to the Ponzo illusion than Western and urban areas (Brislin, 1993) • Carpentered world hypothesis (Segall et al., 1966) people who are raised in an environment made by carpenters tend to interpret nonrectangular figures as representations of rectangular figures seen in perspective • Language impacts the labeling of colors and Europeans may lack words to describe vivid colors (Berry et al., 1992)

26. Certain visual perceptual skills might be related to things like retinal pigmentation (Pollack, 1963) • Colors may be more salient for political reasons e.g., red-China, perception of black and white in the U.S. and in other countries as bad and good (Best et. al., 1975; Williams & Best, 1990) • Jung saw this as a reflection of unpredictability and that nature may have endowed humans with this susceptibility

27. Hearing • Variations in hearing are due to physiological differences caused by age, education training, environmental conditions, and experience

28. Taste • Although people are capable of tasting sweet, sour, salty and bitter, people living near the equator prefer spicier foods than people in the north or south

29. Smell • Underarm secretions may impact the menstrual cycle (Cutler et.al., 1986)

30. Touch • Touch is about pressure, temperature, and pain • Anxiety increases pain • Fear, anger, or stress inhibits it • Prioreceptive sense helps people determine body position and movement

31. The Environment Within • Kinesthesis: The sense of body position and movement of body parts; also called kinesthesia. • Equilibrium: The sense of balance. • Semicircular Canals: Sense organs in the inner ear, which contribute to equilibrium by responding to rotation of the head.

32. Perception of Time • Westerners tend to define time w/ precise measurement • Mediterranean Arabs have 3 types of time i.e., no time at all, now, and forever • Akbar (1991) sees Westerners emphasizing time as a commodity bought and sold for consumption, but in Africa time connects all e.g., Swahili sasa indicating immediacy and zamani indicating a warehouse of time including the ancestors

33. People who feel time pressure move faster than those who don’t e.g., Tokyo 20.7 seconds to cover 100’, London 21.6; New York 22.5; Jakarta 27.2 (Levine & Wolff, 1992) • Some studies indicate age seems to bring a release from those constraints, but this research is inconsistent

34. Consciousness and Culture • Consciousness refers to subjective awareness of one’s own sensations, perceptions and other mental events; • Consciousness is reflected in the beliefs of Moslems, Jewish, Christian, Hindu, Buddhist and other thoughts • Monists believe body and soul are inseparable • Dualists believe body and soul are independent

35. Additional Ideas • Individual consciousness may be dependent on cultural factors (Piaget, 1963; Vygotsky, 1932; Wundt, 1913) • Hallowell (1955) thought people lived within a behavioral environment i.e., a mental representation of time space, and the interpersonal world e.g., Ojibwa Indians whose behavioral environment included self, others, gods, relatives and deceased ancestors therefore, when contemplating a moral action, they think of possible impacts on all including dead ancestors

36. Consciousness in the West • Not necessarily linear • Existentialism & symbolism in literature • Marquez’s Cien Años de Soledad • Cubism and primitivism in painting • Modernism in music

37. Sleep and Cultural Significance of Dreams • Sleep is a nonwaking state of consciousness characterized by general unresponsiveness to the environment and general physical immobility • Responsiveness to external stimulation diminished • Dreams are story-like sequences of images occurring during sleep

38. Bourguignon (1954) • Monophasic cultures value cognitive experiences that take place only during normal waking phases and don’t incorporate dreams into social perception and recognition • Associated with materialistic worldview on psychological experience • Polyphasic cultures value dreams and treat them as part of reality • Associated with the spiritual or traditional view

39. What are dreams? • People used to view dreams as messages from God or as omens of the future • Today we study them as psychological events • Freud was particularly interested in dreams and dream interpretations

40. Dreams tend to reflect expectations • Different cultures view the purpose of dreams differently i.e., as some sort of spiritual information or as latent content reflecting soicocultural reality

41. Types of Dreams • Recurring Dreams • Happen repeatedly • Usually relates to a personality issue, insecurity, or sometimes a preoccupation (something you think about a lot or are very concerned with) • Predictive Dreams • ‘déjà vu’ type dreams where you dream about something that eventually occurs • Unproven and unreliable

42. Types of Dreams (Cont.) • Lucid Dreams • Dreaming while knowing that you are dreaming • Sometimes you can control what happens in your dream • Two Levels of lucid dreams • ‘High Level’ = Dreamer is aware he/she is dreaming and asleep in bed… knows characters and situations aren’t real • ‘Low Level’ = Dreamer is aware he/she is dreaming, but not that he/she is asleep and safe in bed. Often think that dreams and characters are real.

43. Nightmares and Night Terrors • Nightmares • Scary or violent dreams that result from some anxiety which bursts through into dreams • Especially in childhood • Often can relate to past experiences which still cause concern or anxiety • Occur during REM sleep & are usually remembered

44. Nightmares and Night Terrors • Night Terrors • Occur during Stage 4 of NREM sleep & are not remembered • Can’t wake someone up from a night terror… usually takes 10-20 minutes to wake them • Usually not a situation, just panic that strickes while sleeping and accompanied by movement and screams • Children ages 2-6 have these the most common

45. Freud’s Dream Symbolism

46. Freud’s Dream Symbolism

47. More Dream Analysis

48. Beyond Altered States of Consciousness • Altered States of Consciousness (ASC) refers to phenomena that are different from waking consciousness and include mystic perceptual and sensory experiences like meditation, hypnosis, trance and possession (Ward, 1994) • Trance is a sleeplike state with reduced sensitivity to stimuli, loss or alteration of knowledge and automatic motor activity • Mass religious ceremonies, collective prayers, rock concerts, political gatherings can result in trances

49. Trances • Visionary trances are when someone experiences hallucinations • More common in men of hunter-gatherer societies • Possession trances are when someone reports that their body has been capture by one or more spirits • More common in women of non-hunter-gatherer societies • Mass hysteria e.g., Lee & Ackerman (1980) West Malaysia college; Salem witches

50. Meditation • A quiet and relaxed state of tranquility where a person achieves an integration of thoughts, perceptions, and attitudes • Looking for liberation from self or an expansion of conscious awareness • Can reduce stress