Presentation on theme: "Sensation and perception"— Presentation transcript:
1 Sensation and perception 6Sensation and perception
2 6 Definitions Sensation Perception The detection of physical energy emitted or reflected by physical objectsOccurs when energy in the external environment or the body stimulates receptors in the sense organsPerceptionThe process by which the brain organizes and interprets sensory information
3 6Ambiguous figureColored surface can be either the outside front surface or the inside back surface.But not simultaneously bothThe brain can interpret the ambiguous cues in two different ways.
4 Riddle of separate sensations 6Riddle of separate sensationsSense receptorsSpecialized cells that convert physical energy into electrical energy that can be transmitted as nerve impulses to the brain
5 Sensation and perception 6Sensation and perception
6 Specific nerve energies 6Specific nerve energiesDifferent sensory modalities exist because signals received by the sense organs stimulate different nerve pathways leading to different areas of the brain.SynesthesiaA condition in which stimulation of one sense also evokes another
7 6Absolute thresholdThe smallest quantity of physical energy that can be reliably detected by an observer
8 6 Absolute thresholds Vision Hearing Smell Touch Taste A single candle flame from 30 miles on a clear nightHearingThe tick of a watch from 20 feet in total quietSmellOne drop of perfume in a 6-room apartmentTouchThe wing of a bee on the cheek, dropped from 1 cmTasteOne teaspoon of sugar in 2 gallons of water
9 6Difference thresholdThe smallest difference in stimulation that can be reliably detected by an observer when two stimuli are comparedAlso called the Just Noticeable Difference (JND)
10 Signal-detection theory 6Signal-detection theoryA psychophysical theory that divides the detection of a sensory signal into a sensory process and a decision process
11 Sensory adaptation and deprivation 6Sensory adaptation and deprivationAdaptationThe reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitiousPrevents us from having to respond continuously to unimportant informationDeprivationThe absence of normal levels of sensory stimulation
12 6 Sensory overload Over-stimulation of the senses Can use selective attention to reduce sensory overloadSelective attention: the focusing of attention on selected aspects of the environment and the blocking out of others
13 6 Vision What we see An eye on the world Why the visual system is not a cameraHow we see colorsConstructing the visual world
14 6 What we see Hue Brightness Saturation Visual experience specified by color names and related to the wavelength of lightBrightnessVisual experience related to the amount of light emitted from or reflected by an objectSaturationVisual experience related to the complexity of light waves
16 6 An eye on the world Cornea Lens Iris Pupil Protects eye and bends light toward lensLensFocuses on objects by changing shapeIrisControls amount of light that gets into eyePupilAperture through which light reaches the retina
17 6 An eye on the world Retina Rods Cones Neural tissue lining the back of the eyeball’s interior containing the receptors for visionRodsVisual receptors that respond to dim lightConesVisual receptors involved in color vision
18 Structures of the retina 6Structures of the retina
19 6Your turnYou have a hard time locating your red car at night, in the poorly lit mall parking lot. Why?1. Your rods are less sensitive to color in dim light.2. Your cones, which detect color, do not function well in dim light.3. Your ganglion cells receive insufficient overall stimulation to function.4. Your rods, which detect color, do not function well in dim light.
20 6Your turnYou have a hard time locating your red car at night, in the poorly lit mall parking lot. Why?1. Your rods are less sensitive to color in dim light.2. Your cones, which detect color, do not function well in dim light.3. Your ganglion cells receive insufficient overall stimulation to function.4. Your rods, which detect color, do not function well in dim light.
21 The visual system is not a camera 6The visual system is not a cameraMuch visual processing is done in the brainSome 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 detectorsCells in the visual cortex that are sensitive to specific features of the environment
22 Huble and Wiesel’s experiment 6Huble and Wiesel’s experiment
23 6Trichromatic theoryYoung (1802) and von Helmholtz (1852) both proposed that the eye detects 3 primary colorsRed, blue, and greenAll other colors derived by combination
24 Opponent-process theory 6Opponent-process theoryA competing theory of color vision, which assumes that the visual system treats pairs of colors as opposing or antagonisticOpponent-process cells are inhibited by a color, and have a burst of activity when it is removed.
27 Test of color deficiency 6Test of color deficiency
28 6Form perceptionGestalt principles describe the brain’s organization of sensory building blocks into meaningful units and patterns.
29 6 Gestalt principles Proximity Closure Things close to one another are grouped togetherClosureThe brain tends to fill in gaps to perceive complete forms
30 6 Gestalt principles Similarity Continuity Things that are alike are perceived togetherContinuitySeeing continuity in lines that could be interpreted as either continuous or abruptly shifting in direction.
31 6Your turnWhich Gestalt principle is illustrated by the fact that we see columns of dots rather than rows in this diagram?1. Similarity2. Proximity3. Closure4. Continuity
32 6Your turnWhich Gestalt principle is illustrated by the fact that we see columns of dots rather than rows in this diagram?1. Similarity2. Proximity3. Closure4. Continuity
33 Depth and distance perception 6Depth and distance perceptionBinocular cues: visual cues that require the use of both eyesConvergenceTurning inward of the eyes, which occurs when they focus on a nearby objectRetinal disparityThe slight difference in lateral separation between two objects as seen by the right and left eyes
34 Depth and distance perception 6Depth and distance perceptionMonocular cues: visual cues that can be used by one eye
35 The Müller-Lyer illusion 6The Müller-Lyer illusion
36 6Color in contextThe way you perceive a color depends on the color surrounds.
37 6The Ames roomA 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.
38 6Visual constanciesThe accurate perception of objects as stable or unchanged despite changes in the sensory patterns they produceShape constancyLocation constancySize constancyBrightness constancyColor constancy
39 6 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.
40 6 What we hear Loudness Pitch Timbre The dimension of auditory experience related to the intensity of a pressure wavePitchThe dimension of auditory experience related to the frequency of a pressure waveTimbreThe dimension of auditory experience related to the complexity of a pressure wave
42 Auditory localization 6Auditory localizationSounds from different directions are not identical as they arrive at left and right ears.LoudnessTimingPhaseThe brain calculates a sound’s location by using these differences.
43 6 Other senses Taste: savory sensations Smell: the sense of scents Senses of the skinThe mystery of painThe environment within
44 Taste: savory sensations 6Taste: savory sensationsPapillaeKnoblike elevations on the tongue, containing the taste budsTaste budsNests of taste-receptor cells
45 6 Taste buds 10,000 taste buds line the tongue and mouth Receptors are down inside the “bud”.Children have more taste buds than adults.
46 6 Four tastes Five basic tastes Salty, sour, bitter, sweet, and umamiDifferent people have different tastes based on:GeneticsCultureLearningFood attractiveness
47 Smell: The sense of scents 6Smell: The sense of scentsAirborne chemical molecules enter the nose and circulate through the nasal cavity.Vapors can also enter through the mouth and pass into nasal cavity.Receptors on the roof of the nasal cavity detect these molecules.
50 Gate-control theory of pain 6Gate-control theory of painExperience of pain depends in part on whether the pain gets past a neurological “gate” in the spinal cord.
51 Neuromatrix theory of pain 6Neuromatrix theory of painThe matrix of neurons in the brain is capable of generating pain (and other sensations) in the absence of signals from sensory nerves.
52 The environment within 6The environment withinKinesthesisThe sense of body position and movement of body partsEquilibriumThe sense of balanceSemicircular canalsSense organs in the inner ear, which contribute to equilibrium by responding to rotation of the head
53 Inborn abilities: The visual cliff 6Inborn abilities: The visual cliffGlass surface, with checkerboard underneath at different heightsVisual illusion of a cliffBaby can’t fallMom stands across the gap.Babies show increased attention over deep side at age 2 months, but aren’t afraid until about the age they can crawl.
54 6Critical periodIf 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.
55 Psychological and cultural influences 6Psychological and cultural influencesWe 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.Perceptual set: a habitual way of perceiving, based on expectationsAll are influenced by culture.
57 6PrimingA method used to insure unconscious processes, in which a person is exposed to information and is later tested to see whether the information affects behavior or performance on another task or in another situationFindings suggest simple primes influence perception, memory, thinking, and decision-making.
58 Perception vs. persuasion 6Perception vs. persuasionAlthough subliminal priming can influence judgments and preferences, research doesn’t support its success in major levels of persuasion.
59 Extrasensory perception 6Extrasensory perceptionESPThe ability to perceive something without ordinary sensory informationHas not been scientifically demonstrated
60 6ParapsychologyJ. B. Rhine conducted many experiments on ESP using stimuli such as these.Rhine believed his evidence supported ESP, but his findings were flawed.