Sensation and perception 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-bottum up Perception The process by which the brain organizes and interprets sensory information-top Down 1
Perceiving Our World Translation of information into sensory experience. Joel Carillet/iStockphoto L02 L03 L04 L05 L0 L07 L08 Transduction Sue Williams and Adrian G. Dyer Transduction: Translation of information from the environment into neural signals 2
Specific nerve energies Different sensory modalities exist because signals received by the sense organs (eyes etc..) stimulate different nerve pathways leading to different areas of the brain. Synesthesia A condition in which stimulation of one sense (hearing) also evokes another (vision) Sensory adaptation and deprivation Adaptation The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious Prevents us from having to respond continuously to unimportant information Deprivation The absence of normal levels of sensory stimulation. To some degree, Our response depends on our expectations and our interpretations. 3
Sensory overload Over-stimulation of the senses Can use selective attention to reduce sensory overload. The cocktail party phenomenon Selective attention: the focusing of attention on selected aspects of the environment and the blocking out of others. May also cause innattentional blindness What we see Hue Visual experience specified by color names and related to the wavelength of light Brightness Visual experience related to the amount of light emitted from or reflected by an object Saturation Visual experience related to the complexity of light waves 4
What we see An eye on the world 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 Aperture through which light reaches the retina 5
An eye on the world Retina Neural tissue lining the back of the eyeball s interior containing the receptors for vision Rods Visual receptors that respond to dim light Cones Visual receptors involved in color vision. Do not respond well in dim light. On reason it might be hard to find a red car in a dark parking lot. Structures of the retina
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 cortical cells 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 Huble and Wiesel s 1981 Nobel Prize 7
How we see colors: Trichromatic theory Young (1802) and von Helmholtz (1852) both proposed that the eye detects 3 primary colors Red, blue, and green All other colors derived by combination Color in context The way you perceive a color depends on the color surrounds. 8
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. Afterimages 9
Test of color deficiency 10
Form perception Gestalt principles describe the brain s organization of sensory building blocks into meaningful units and patterns. Gestalt principles Proximity Things close to one another are grouped together Closure The brain tends to fill in gaps to perceive complete forms 11
Gestalt principles Similarity Things that are alike are perceived together Continuity Seeing continuity in lines that could be interpreted as either continuous or abruptly shifting in direction. Depth and distance perception Binocular cues: visual cues 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 right and left eyes 12
Depth and distance perception Monocular cues: visual cues that can be used by one eye 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 inches in front of face. 13
The Müller-Lyer illusion 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 use of binocular depth cues. 14
Have you been to the Mystery Spot? SPOILER WARNING: :-) Habituation to a steep gradient Similar to an Ames room. See article on my site. http://www.exploratorium.edu/ h#p://www.illusionworks.com/ index.html Critical periods If infants miss out on experiences during a crucial period of time, perception will be impaired. When adults who have been blind since birth have vision restored, they may not see well. Other senses such as hearing may be influenced similarly. 15
3/20/13 Development of Perception Click on play bu#on to launch video in QuickTime player. L01 L02 L03 L04 L05 L0 L07 L08 How Does Sensation Lead to Perception? How Do We See? How Do We Hear? How Do We Feel Body Position, Touch, Temperature, and Pain? How Do We Process Smells and Tastes? Psych-socio-cultural influences We are more likely to perceive something when we need it. What we believe can affect what we perceive. Emotions, such as fear, can influence perceptions of sensory information. Expectations based on previous experiences can influence perception. Hello Walter! vs. Shallow Water. Perceptual set: a habitual way of perceiving, based on expectations All are influenced by culture. Rural Africans are less susceptible to the Muller-Lyer illusion because they live in a less carpentered world (round huts) 1
ESP or Extrasensory perception: The field of Parapsychology ESP - (telepathy, precognition) The ability to perceive something without ordinary sensory information. Has been studied extensively but studies have been poorly designed with inadequate precautions against fraud. After an exhaustive review, the National Research Council Concluded that there was No scientific justification.for the existence of parapsychological phenomena. BUT, the issue isn t gone is it? Many people really really WANT to believe in ESP. Perhaps for some good reasons, discussed next week. Consider the story of James Randi (The Amazing Randi), Dr. Andrew Weil, and Uri Geller. How Do We Feel Body Position, Touch, Temperature, L01 L02 and Pain? L03 L04 L05 L0 L07 L08 Summarize the mechanisms by which the somatosensory and chemical sense systems produce perception of body position, touch, temperature, pain, smell, and taste. Pp. 217-223 17
Body Position: The Vestibular System Facial nerve Cochlear nerve Cochlea Vestibular nerve Utricle Saccule Semicircular canals Argosy Publishing, Inc. L01 L02 L03 L04 L05 L0 L07 L08 How Does Sensation Lead to Perception? How Do We See? How Do We Hear? How Do We Feel Body Position, Touch, Temperature, and Pain? How Do We Process Smells and Tastes? The Sense of Touch Argosy Publishing, Inc. L01 L02 L03 L04 L05 L0 L07 L08 How Does Sensation Lead to Perception? How Do We See? How Do We Hear? How Do We Feel Body Position, Touch, Temperature, and Pain? How Do We Process Smells and Tastes? 18
Close Relationships and Pain pp. 231 In one study, women who were expecting an electric shock reported les pain showed reduced activity in emotional and arousing parts of the brain associated with pain when they held their partners hand. The reduction in pain was associated with the selfreported quality of their marriage. Healing at a Distance & ESP? Studies at the Institute for Noetic Sciences have provided evidence for potential for healing even thinking positive thoughts towards a loved one when they are pain. What do you think? http://noetic.org/research/project/ compassionate-intention-prayer-anddistant-healing/reading/ I think the methods look good and the results are intriguing. But remember, Science requires a skeptical stance.but speculation creates testable theories! 19
Write about it! Write All About It How might you personally use the knowledge that physical contact with a loved one can affect the way we experience pain? What other applications of this information do you envision? 20