PART 1: SENSATION AND PERCEPTION/CH 4

Sensation & PerceptionPART I : Sensation & PerceptionPART I AP PSYCHOLOGY

Sensation : Sensation Sensation a process by which our sensory receptors and nervous system receive and represent stimulus energy You detect physical energy from your environment and encode it as neural signals

Sensation : Sensation Our sensory and perceptual processes work together to help us sort out complex processes

How Many Wolves? : How Many Wolves?

Perception : Perception Perception a process of selecting, organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

Perception : Perception According to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in what oredr the ltteers in a wrod are, the olny iprmoetnt tihng is that the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can still raed it wouthit porbelm. This is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

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Perception : Perception Selective Attention focus of conscious awareness on a particular stimulus Cocktail Party Effect

Sensation- Basic Principles : Sensation- Basic Principles Psychophysics study of the relationship between physical characteristics of stimuli and our psychological experience of them Gustav Fechner Published work that laid foundation for Wundt’s work

Topics in Psychophysics : Topics in Psychophysics Threshold dividing point between energy levels that do and do not have a detectable effect. Absolute Threshold minimum stimulation needed to detect a particular stimulus 50% of the time Just Noticeable Difference minimum difference between two stimuli required for detection 50% of the time AKA – Difference Threshold

Slide 12 : An absolute threshold is the minimal amount of sensory stimulation needed for a sensation to occur.

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JND: Weber’s Law : JND: Weber’s Law Weber’s Law Difference thresholds increase in proportion to the size of the stimulus Formula: JND is 1/30 of stimulus Weight Example Can you detect the difference between 30 & 31 oz of weight? Yes. 1/30 of 30 = 1 (JND) You can tell the difference between 30 & 31 because the JND is 1 and the difference in weight is one oz. Can you detect the difference between 90 & 91 oz of weight? No. 1/30 of 90 = 3 (JND) You cannot tell the difference in weight because there is only a 1 oz diff. You can only tell a difference in weight per every 3 ounce shift. You could tell the difference between 90 and 93, however.

JND: Fechner’s Law : JND: Fechner’s Law The magnitude of a sensory experience is proportional to the number of JND’ s that the stimulus causing the experience is above absolute threshold. 3 EQUAL INCREASES IN STIMULUS INTENSITY PRODUCE PROGRESSIVELY SMALLER DIFFERENCES IN THE MAGNITUDE OF THE SENSATION… AND SO FORTH. Light bulb phenomena- adding light doesn’t double the light in a room

Sensation- Thresholds : Sensation- Thresholds Signal Detection Theory predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) assumes that there is no single absolute threshold detection depends partly on person’s experience expectations motivation level of fatigue

4 Possible Outcomes in Signal Detection Theory : 4 Possible Outcomes in Signal Detection Theory Hits Detecting signals when present Misses Failing to detect signals when they are present False alarms Detecting signals when they are not present Correct rejections Not detecting signals when they are absent

SUBLIMINAL PERCEPTION : SUBLIMINAL PERCEPTION The registration of sensory input without conscious awareness Sensing something below your threshold for awareness

Sensation- Thresholds : Sensation- Thresholds Subliminal When stimuli are below one’s absolute threshold for conscious awareness

Subliminal Perception Research : Subliminal Perception Research James Vicary 1957 Popcorn and Theater Sparked more research on topic of sublimation

Slide 25 : Brian Key Commercial Subliminals Author on subject Backward Masking 80’s music

Slide 26 : Krosnik’s Empirical study 1992 Behavior modification and subliminal stimuli Perception without awareness can take place No evidence subliminal messages can mold behavior

Sensory Adaptation : Sensory Adaptation Gradual decline in sensitivity to prolonged stimulation Automatic built in human process Smell something strong- over time it seems to dissipate Tactile Sensory Adaptation

Slide 28 : The body receives information through the five main senses. The Five Human Senses Hearing Vision Taste Smell Touch

The Visual System: Sight : The Visual System: Sight Light- electromagnetic radiation traveling as a wave The spectrum of electromagnetic energy

Vision- Physical Properties of Waves : Vision- Physical Properties of Waves Light Waves 3 properties of light Wavelength Distance between peaks color Amplitude Height brightness Purity Mixtures of wavelengths Variation of mixtures Saturation (richness of color)

Vision- Physical Properties of Waves : Vision- Physical Properties of Waves

Vision : Vision Transduction conversion of one form of energy to another in sensation, transforming of stimulus energies into neural impulses Wavelength the distance from the peak of one wave to the peak of the next

Vision : Vision Hue dimension of color determined by wavelength of light Intensity amount of energy in a wave determined by amplitude brightness loudness

Vision: The Eye : Vision: The Eye

Vision : Vision Cornea– the outer covering of the eye Pupil- adjustable opening in the center of the eye

Vision : Vision Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

Vision : Vision Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina Acuity- the sharpness of vision

The Eye: A Living Optical Instrument : The Eye: A Living Optical Instrument 2 Purposes Channel Light House Neural tissue Creates an image of the visual world on the light-sensitive retina How?

Slide 39 : Light enters at cornea Cornea and Crystalline Lens form upside down image on retina Brain makes sense of image and transmits it to your awareness. LIGHT

Slide 40 : Lens Transparent eye structure Focuses light rays falling on the retina Soft tissue Accommodation Adjustments made to alter visual focus Close objects- fatter/rounder Distant objects- flatten out Cornea Transparent, curved layer in front of eye Bends incoming light rays

Focusing Problems : Focusing Problems Nearsightedness See well close up, not far away Light fall short of retina Cornea or lenses bend light too much or the eyeball is too long Farsightedness See well far away, not close up Light from close objects falls behind the retina Eyeball is too short

Vision : Vision Farsighted Nearsighted Normal Vision Vision Vision

IRIS & PUPIL : IRIS & PUPIL IRIS Colored ring of muscle Surrounds the pupil Regulates size of pupil opening PUPIL Black center of eye Opening in center of iris Helps regulate amount of light passing into rear chamber of eye

Constriction & Dilation : Constriction & Dilation Constriction When pupil constricts it Lets less light into eye Sharpens the image falling on the retina Dilation When the pupil opens it Lets more light in Image is less sharp Bright Light- pupils constrict Dim Light- pupils dilate

THE RETINA : THE RETINA The brain’s envoy in the eye Light sensitive surface in back of eye Contains rods and cones Has layers of bipolar cells and ganglion cells transmit visual info to brain

Optic Disk : Optic Disk Whole in retina where optic nerve fibers exit the eye Optic Disk

Visual Receptors: Rods & Cones : Visual Receptors: Rods & Cones

2 Types of Photoreceptors in the Retina : 2 Types of Photoreceptors in the Retina Rods peripheral retina detect black, white and gray twilight or low light Cones near center of retina fine detail and color vision daylight or well-lit conditions

Slide 49 : Rods Cones

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Rods Review : Rods Review Photoreceptors that detect black, white, and gray Detect movement Purpose Peripheral and dim-light vision Distributed through retina None in the fovea

Cones Review : Cones Review Photoreceptors that Detect color Find detail in daylight or in brighter conditions Fovea None in the periphery Don’t respond well in dim light Better visual acuity than rods

Fovea : Fovea Small are of the retina in the most direct line of sight Where cones are most concentrated for highest visual acuity in bright light

Dark and Light Adaptation : Dark and Light Adaptation Dark Adaptation Adjusting to the darkness Camping theater Light Adaptation Eyes become less sensitive to light in high illumination Why does this occur? Chemical changes in rods and cones Neural changes in the receptors and in retina

Information processing in the retina : Information processing in the retina Light strikes rods and cones Creates neural signals Signals sent along optic nerve Axons exit optic nerve through the optic disk Information sent to the brain

Before the information is sent to the brain : Before the information is sent to the brain Processing goes on in the retina before the info goes to the brain 100 million rods and cones combine and travel along 1 million axons in the optic nerve Receptive field- retinal area that affects the firing of that cell Lateral Antagonism- occurs when neural activity in a cell opposes activity in surrounding cells

Vision and the Brain : Vision and the Brain Light falls on the eye but you see with your brain How does visual information get to the brain? Axons Optic Chiasm Two Pathways Thalamus (way station of the brain) Magnocellular channel Parvocellular Channel Superior Colliculus (in midbrain) Parallel Processing Simultaneously extracting different kinds of info from the same input

Visual Information Processing : Visual Information Processing Parallel Processing simultaneous processing of several aspects of a problem simultaneously

Processing Visual Information : Processing Visual Information Ganglion cells— neurons that connect to the bipolar cells, their axons form the optic nerve Bipolar cells— neurons that connect rods and cones to the ganglion cells Optic chiasm— point in the brain where the optic nerves from each eye meet and partly crossover to opposite sides of the brain

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Information Processing in the Visual Cortex : Information Processing in the Visual Cortex Primary Visual Cortex- occipital lobe Hubel and Wiesel Research done with cats Nobel Prize Identified special types of cells in PVC Simple clues Complex cells Why is this research important? Specializations Feature detectors

Color Vision : Color Vision Lights are mixtures of various wavelengths Longest wavelengths= red Shortest wavelengths= violet Three Parts of Light Wavelength- hue Amplitude- brightness Purity- saturation 2 kinds of color mixtures Subtractive- removal of some wavelengths of light Additive- color mixing by superimposing light

Color Mixing : Color Mixing Two basic types of color mixing subtractive color mixture example: combining different color paints additive color mixture example: combining different color lights

Subtractive Color Mixture : Subtractive Color Mixture +

Additive Color Mixture : Additive Color Mixture By combining lights of different wavelengths we can create the perception of new colors Examples: red + green = yellow red + blue = purple

Color Blindness : Color Blindness Most people with color-deficient vision are not color blind. Dichromate Not completely color blind Make due with only two color channels Most common dichromate is red-green deficient

Color Blindness : Color Blindness Photo and clips seen by normal person. Photo and clips are seen by a yellow-blue blind person. Photo and clips are seen by a totally color blind person. Photo and clips seen by a red-green blind person.

Slide 68 : Color Vision Some people cannot tell the difference between certain colors. The most common form is the inability to see the colors of red or green.

Color-Deficient Vision : Color-Deficient Vision People who suffer red-green blindness have trouble perceiving the number within the design

Color Vision : Color Vision Our visual system interprets differences in the wavelength of light as color Rods are color blind, but with the cones we can see different colors This difference occurs because we have only one type of rod but three types of cones

Trichromatic Theory of Color Vision : Trichromatic Theory of Color Vision Researchers found that by mixing only three primary lights (usually red, green and blue), they could create the perceptual experience of all possible colors This led Young and Helmholtz to propose that we have three different types of photoreceptors, each most sensitive to a different range of wavelengths

Visual Information Processing : Visual Information Processing Trichromatic (three color) Theory of Color Vision Young and Helmholtz three different retinal color receptors red green blue

Opponent Process Theory of Color Vision : Opponent Process Theory of Color Vision Edward Hering Some aspects of our color perception are difficult to explain by the trichromatic theory alone Example: afterimages if we view colored stimuli for an extended period of time, we will see an afterimage in a complementary color

Opponent Process- Afterimage Effect : Opponent Process- Afterimage Effect

ComplementaryAfterimages : ComplementaryAfterimages

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Opponent-Process Theory : Opponent-Process Theory To account for phenomena like complementary afterimages, Herring proposed that we have two types of color opponent cells red-green opponent cells blue-yellow opponent cells Black-white opponent cells

Which theory is correct? : Which theory is correct? Our current view of color vision is that it is based on both the trichromatic and opponent process theory George Wald-Nobel Prize Winner 3 types of cones Each sensitive to a different band of wavelengths (colors) Supports the trichromatic theory Other Research Cells in retina and visual cortex respond positively to red versus green and blue versus yellow Ganglion cells in retina are excited by green and inhibited by red Supports the opponent processing theory

Overview of Visual System : Overview of Visual System The eye is like a camera, but instead of using film to catch the light we have rods and cones Cones allow us to see fine spatial detail and color, but cannot function well in dim light Rods enable us to see in dim light, but at the loss of color and fine spatial detail Our color vision is based on the presence of 3 types of cones, each maximally sensitive to a different range of wavelengths

Perceiving Forms, Patterns, and Objects : Perceiving Forms, Patterns, and Objects

REVERSIBLE FIGURES : REVERSIBLE FIGURES Drawing compatible with two interpretations that can shift back and forth Based on your perception, you will see one or the other

Jazz lady : Jazz lady

Donkey or Seal? : Donkey or Seal?

Duck or Rabbit? : Duck or Rabbit?

Duck or Rabbit : Duck or Rabbit

Face or Dragon? : Face or Dragon?

Young Lady or Old Lady? : Young Lady or Old Lady?

Young Woman or Old Lady? : Young Woman or Old Lady?

Old Man, Old Lady, Young Lady : Old Man, Old Lady, Young Lady

Mirror or Devil Face? : Mirror or Devil Face?

Angel bats : Angel bats

How do you perceive forms? : How do you perceive forms? Subjectively More than receiving signals (sensory input) Involves the interpretation of those signals (sensory input) Not just as simple as S-R psychology

Our Interpretation of Stimuli : Our Interpretation of Stimuli Expectation Provided Information or Cues Perceptual Set Readiness to perceive a stimulus in a particular way Organization Feature Analysis

Perceptual Set: A readiness to perceive a stimulus in a particular way : Perceptual Set: A readiness to perceive a stimulus in a particular way Selection What you focus your attention on can effect your perceptual set Inattentional Blindness (AKA-change blindness) Failure to see fully visible objects or events in a visual display

Inattentional Blindness : Inattentional Blindness

Feature Analysis: Assembling Forms : Feature Analysis: Assembling Forms Process of detecting specific elements in visual input and assembling them into a more complex form. Bottom-Up Processing Top-Down Processing Subjective contours

Bottom-Up Processing : Bottom-Up Processing Analysis that begins with the sense receptors and works up to the brain’s integration of sensory information Progresses from individual elements to whole elements. Detect specific features of stimulus Combine specific features into more complex forms Recognize Stimulus

Top-Down Processing : Top-Down Processing Information processing guided by higher-level mental processes Progresses from the whole to the individual parts Formulate perceptual hypothesis about the nature of the stimulus as a whole Select and examine features to check hypothesis Recognize stimulus As when we construct perceptions drawing on our experience and expectations

Subjective Contours : Subjective Contours Top-Down Processing You perceive contours (boundaries) where none exist

Invisible Triangle : Invisible Triangle

Looking at the whole picture: Gestalt Principles : Looking at the whole picture: Gestalt Principles “the whole can be greater than the sum of its parts” Top-Down Processing at work in Gestalt Psychology EX: Phi Phenomenon The illusion of movement created by presenting visual stimuli in rapid succession Picture book Motion pictures

Motion Perception : Motion Perception Phi Phenomenon an illusion of movement created when two or more adjacent lights blink on and off in succession. (Christmas lights)

Figure and Ground: Organization in the visual system (top-down) : Figure and Ground: Organization in the visual system (top-down) People organize visual perceptions by dividing visual displays into what is there (figure) and the backdrop (ground) Figure More presence Seem closer Ground Appear farther away Less prominent

Perceptual Organization : Perceptual Organization Figure and Ground--organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Goblet or Faces? : Goblet or Faces?

Faces or Vases? : Faces or Vases?