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