SENSASI DAN PERSEPSIPsikologi Umum 2Universitas Bunda Mulia
Sensation and Perception
Measuring the Sensory ExperienceSensationPerceptionExtrasensory Perception
Sensation & Perception Processes
Psychophysics
PsychophysicsThe study of the relationship between physical stimulation and subjective sensations.
Signal-Detection TheoryThe theory that detecting a stimulus is jointly determined by the signal and the subject’s response criterion.
Thresholds
Absolute ThresholdThe smallest amount of stimulation that can be detected
Just Noticeable DifferenceThe smallest amount of change in a stimulus that can be detected
Absolute Sensory ThresholdsVision: A single candle flame from 30 miles on a dark, clear nightHearing: The tick of a watch from 20 feet in total quietSmell: 1 drop of perfume in a 6-room apartmentTouch: The wing of a bee on your cheek, dropped from 1 cmTaste: 1 tsp. Sugar in 2 gal. water
The Electromagnetic Spectrum
The Electromagnetic Spectrum
Structures of the Human Eye
Visual Pathways
The Retina
Differences Between Rods and ConesDifferences Between Rods and Cones
Are numerous and found primarily in the peripheral retinaHave a lower threshold for activationHave lower acuityDo not process color
Are concentrated primarily in the foveaHave a higher threshold for activationHave higher acuityProcess color
RodsRods ConesCones
Hubel & Wiesel’s Experiment
Some cells in the visual cortex respond only to certain types of visual information
For example, a diagonal line moving up and down
These cells are called feature detectors
Trichromatic TheoryT. Young (1802) & H. von Helmholtz (1852) both proposed that the eye detects 3 primary colors
red, blue, & greenAll other colors can be derived by combining these three
Afterimages
The Color WheelSpectral colors vary from Violet-Blue to Red
470 to 700 nanometer wavelength
Purple and red-purple are non-spectral colors
Not found on the visible electromagnetic spectrum
Across the wheel, each color has its complement
Test of Color Deficiency
The Human Ear
Auditory LocalizationSounds from different directions are not identical as they arrive at left and right ears
LoudnessTimingPhase
The brain calculates a sound’s location by using these differences
Olfactory System
Taste Buds
Photograph of tongue surface (top), magnified 75 times10,000 taste buds line the tongue and mouth
Taste receptors are down inside the “bud”
Children have more taste buds than adults
Sensitivity to Touch
PerceptionMotivation and Attention:
We do not perceive everything in our environment; our motives greatly influences our perceptionDriving down the road, very hunger all you seem to notice is fast food billboards.Then you notice that the gas gauge is running on empty. How are your perception altered?
AttentionWe cannot possibly attend to and process all of the stimuli received by our sensory systemsDichotic listening exercises (Goodwin, 1988)Divided Attention
“cocktail party phenomenon” (Cherry & Bowles, 1960)
Basic Perceptual Abilities: Patterns and Constancies
Pattern PerceptionFeature detectorsFeature Analysis Theory of Pattern Perception (Lindsay & Norman, 1977)
Theory of pattern perception stating the we perceive basis elements of an object and assemble them mentally to create the complete object.
Basic Perceptual Abilities: Patterns and Constancies
Perceptual ConstancyShape ConstancySize Constancy
C.M. Turnbull (1961)Auditory Constancies
How are we able to recognize a melody, when it is played on different instruments and in different keys?
Shape ConstancyEven though these images cast shadows of different shapes, we still see the quarter as round
Depth Perception
The ability to perceive our world three –dimensionally. Two type of cues:
Binocular cuesAdjustments of the eye muscles Binocular Disparity
Monocular cuesSuperpositionTexture GradientLinear PerspectiveRelative Brightness
The Visual Cliff
Devised by Eleanor Gibson and Richard Walk (1960) to test depth perceptionGlass surface, with checkerboard underneath at different heights
Visual illusion of a cliffBaby can’t fall
Mom stands across the gapBabies aren’t afraid until about the age they can crawl
Gestalt Principle of Perceptual Organization
The founders of Gestalt psychologyMax WertheimerWolfgang KohlerKurt Koffka
We are born with the ability to organize the elements of our perceptual world in very predictable ways.The goal of these automatic processes is to produce the most complete perception of the environment.
Figure and Ground
“It may take a magician to pull a rabbit out of a hat, but we all possess sufficient magic to pull a duck out of a rabbit.”
R. N. Shephard, 1990
Figure and Ground
Principles of GroupingProximity
Seeing 3 pair of lines in ASimilarity
Seeing columns of orange and red dots in B
ContinuitySeeing lines that connect 1 to 2 and 3 to 4 in C
ClosuresSeeing a horse in D
Perception of MovementTheater marquees and electronic billboards suggestion that the words are moving across the sign. But are they?Apparent Motion
The illusion of movement in a stationary object.Movies, television, videocassette
Autokinetic effect
Perceptual Hypotheses and IllusionsPerceptual Hypothesis
Inference about the nature of stimuli received from the environment
Perceptual IllusionsMisperceptions or interpretations of stimuli that do not correspond to the sensations received.
The Ames RoomA specially-built room that makes people seem to change size as they move around in itThe room is not a rectangle, as viewers assume it isA single peephole prevents using binocular depth cues
Contemporary Issue and Findings
Parallel Processing (Friedman-Hill & Wolfe, 1995
Processing does not occur in a strictly sequential manner (Zeki, 1993)
Visual SearchFive different cones (Neitz, Neitz & Grishok,
1995)Application of Basic Research
Dyslexia
Perceptual Set
What you see in the center figures depends on the order in which you look at the figures:
If you scan from the left, see an old womanIf you scan from the right, see a woman’s figure
Context EffectsThe same physical stimulus can be interpreted differentlyWe use other cues in the situation to resolve ambiguitiesIs this the letter B or the number 13?
The Ponzo Illusion
Linear perspective provides contextSide lines seem to convergeTop line seems farther away
But the retinal images of the red lines are equal!
ParapsychologyGallop & Newport (1991) survey
93 percent believed in at least one paranormal or psychic phenomenon1/3 believed in reincarnation1/3 believed in communication with the dead½ believed that their dreams could predict event such as the death of a family member.
Parapsychology
J. B. Rhine conducted many experiments on ESP using stimuli such as these Zener CardsRhine believed that his evidence supported the existence of ESP, but his findings were flawed
Thinking Critically About ESP
Psychics exploit unquestioning minds“Psychic Abscam”(1983)“A psychic is an actor playing the role of a psychic”, Daryl Bem (1984)
Layton and Turnbull, clairvoyance experiment.Daryl Bem and Charles Honorton (1994) The Ganzfeld Procedure
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