Sensation and Perception

Unit 4AO lny srmat poelpe can raed this.docx

Unit Overview• Sensing the World: Some Basic Principles• Vision• Hearing• Other Senses• Perceptual Organization• Perceptual Interpretation• Is there Extrasensory Perception?

Click on the any of the above hyperlinks to go to that section in the presentation.

1. What are Sensation and Perception? What do we mean by bottom up processing and top-down processing?

• Sensation the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

• Perception the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

• Are one continuous process• “ We perceive the world not exactly as it is, but as it

is useful for us to perceive it ”

Introduction

• Bottom-up processing = starts at our sensory receptors and works up to the brain

• No Prior Knowledge

• Top-down processing = we construct perceptions drawing on experience and expectations.

• Prior Knowledge, stereotyping

The Forrest has Eyes – Bev Doolittle

The Forrest Has Eyes

• Bottom up processing : we receive sensory information on the horses and riders in the painting

• Top down processing: we perceive faces in the forests and rivers based on our experience and expectations of what faces look like.

2. How are we affected by selective attention?Selective Attention = the focusing of conscious awareness on a

particular stimulus.

- Cocktail Party Effect - Our ability to focus on a conversation in a crowded and loud environment.

- Cell Phone use and Car Accidents :

- Texting and Driving Statistics

Inattentional blindness

= failing to see visible objects when our attention is directed elsewhere.

Change Blindness = failing to notice a change

Selective Attention Test

3. What are the absolute and difference thresholds, and do stimuli below the absolute threshold have any influence?• Psychophysics = the study of relationships between the

physical characteristics of stimuli, such as their intensity, and our psychological experience of them.

• Absolute threshold = the minimum stimulation necessary to detect a particular stimulus 50% of the time.

• Signal detection theory = a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and altertness.

• Examples: • In war, failure to detect an intruder could be fatal. So soldiers on

guard, who are responsible for others lives, might be more likely to detect an almost imperceptible noise, because they will be more focused.

• TSA Scanners monitoring bags, Nurses monitoring ICU patients, Air Traffic Controllers watching the radar.

• How soon would you notice an incoming text if (1) you are expecting a particular one, (2) it is important that you detect it, (3) you are alert.

• Subliminal = below one’s absolute threshold for conscious awareness.

• Priming = the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.

• Difference threshold (JND) = the minimum difference between two stimuli required for detection. We experience the difference threshold as a just noticeable difference.

• Weber’s law = the principle that, to be perceived as different, two stimuli must differ by a constant percentage (rather than a constant amount).

Just noticeable difference

4. What is the function of Sensory Adaptation?• Sensory adaptation = diminished sensitivity as a consequence

of constant stimulation.

• After constant exposure to stimulus, our nerve cells fire less frequently.

• Examples: • You enter a neighbors living room and smell a musty odor. You

wonder how they can stand it, but after a few minutes you no longer notice it.

• Move your watch up your wrist by one inch. You will feel it but only for a few moments.

• So why if we stare at an object without flinching it doesn’t vanish from sight?

• Our eyes are constantly moving, flitting from one spot to another enough to guarantee that stimulation continuously changes.

• What if we could stop our eyes from moving?• Psychologists have devised an instrument that is a miniature projector

attached to a contact lens. When the eye moves, so does the image. So the stimulus is always the same.

• At first we would see the full picture but it would shift with time

Short Response

• 1. What are Sensation and Perception? What do we mean by bottom up processing and top-down processing?

• 2. How are we affected by selective attention?• 3. What are the absolute and difference thresholds, and

do stimuli below the absolute threshold have any influence?

• 4. What is the function of Sensory Adaptation?

Sensation and Perception: Vision, Hearing, and other

senses

Unit 4B

Vision

1. What is energy that we see as visible light?The Stimulus Input: Light EnergyUsing your book, define the words below

•Transduction (transform)•Wavelength•Hue (color)

• Wavelength

• Intensity• Wave amplitude

Electromagnetic Energy SpectrumWe see only a small portion of the spectrum of electromagnetic energy

The Eye: 2. How does the eye transform light energy into neural messages?Define the following terms

• Light enters the Cornea• Passes the: Pupil• And the: Iris• Goes to the: Lens which

• Accommodation focuses the image on the:

•Retina

The EyeThe Retina

•Rods and Cones

Rods:Black & WhitePeripheral detection

Cones: Color &Detail

Rods versus Cones

The Retina’s Reaction to Light 2. How does the eye transform light energy into neural messages?

Visual Information ProcessingFeature Detection

•Feature detectors: cells that activate and respond to specific features

Visual Information ProcessingParallel Processing

•Parallel processing: the brain divides a scene into sub dimensions such as color, movement, form and depth

• Blind sight

Visual information processing

Color Vision•Young-Helmholtz trichromatic (three color) theory:

• The eye has 3 color receptors• Red, green, blue• When the cones are stimulated in

combination, we see diffrerent colors

• Ex, yellow = green + red cones

Color Vision

• Opponent-process theory: • We see one color because the other

is off.

• Three sets of opposite colors

• Red-green• Blue-yellow• Black-white

• Afterimage

After image: stare at the center for 1 min.

Summary:

Color Processing happens in two stages:•Retina’s green, red and blue cones respond to stimuli•Then signals are processed by nervous systems opponent (opposite) process cells.

•How we see color - Colm Kelleher

1. Define all the key terms from pages 124 – 133 (18 total)

2. What is energy that we see as visible light?

3. How does the eye transform light energy into neural messages?

4. How does the brain process visual information?

5. What process takes place when we recognize a face?

6. What two theories help us understand color vision?

Hearing: Define key terms pg 134-150 (15)

2. How does the ear transform sound energy into neural messages? Read page 135, F 4.19

Hearing Loss and Deaf Culture:3. What are the two types of common hearing loss? And how do cochlear implants help? (Read pg 138)

•Hearing loss• Conduction hearing loss• Sensorineural hearing loss• Cochlea implant• Cochlear Controversy

Living in a Silent World

• 4. Describe the challenges faced by deaf people who have been separated from a supportive society.

• Read Close Up on page 139

Biopsychosocial approach to pain:5. Outline the Biopsychosocial approach to pain. (pgs 143-145)

Taste:6. List the survival functions of Basic Taste.

•Sweet, sour, salty and bitter• Umami

•Taste buds• Chemical sense

•Age and taste

Smell (olfaction): 7. Ho do we experience smell?

Summary1. Define key terms pg 134-150 (14)

2. How does the ear transform sound energy into neural messages?

3. How does the ear transform sound energy into neural messages?

4. Describe the challenges faced by deaf people who have been separated from a supportive society.

5. Outline the Biopsychosocial approach to pain.

6. List the survival functions of Basic Taste.

Sensation and Perception:Perceptual Interpretaion

Unit 4C

1. Perceptual OrganizationHow does our brain Organize Sensory Information?

Gestalt

• Gestalt – an organized whole

• Gestalt psychologist emphasize our tendency to integrate pieces of information in to meaningful wholes.

• Hence we perceive a cube instead of blue circles containing white lines.

Form PerceptionFigure and Ground

•Figure-ground – organizing our visual field into objects (figures) that stand out from their surroundings (background)

Form Perception

•Grouping• Proximity – we group nearby figures together• Similarity – we group similar figures together• Continuity – We perceive smooth continuous patterns.

• Connectedness – we connect uniform and linked figures.

• Closure – We fill in the gaps to complete objects

Depth Perception2. How do we Perceive distance and depth (use your eyes)

• Depth perception= the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance.

• Visual Cliff

Binocular Cues : use 2 eyes

Convergence – Refers to signals sent from muscles that turn the eyes.

To focus on near or approaching objects, these muscles turn the eyes inward.

The brain uses the signal sent from these muscles to determine the distance of the object.

Binocular Cues : use 2 eyes

• Retinal Disparity - Depth cue that depends on the distance to the eyes. Because of their different positions, each eye receives a slightly different image. The difference between the right and left eyes’ images is the retinal disparity. The brain interprets a large retinal disparity to mean a close object and a small retinal disparity to mean a distant object.

Mononocular Cues : Use 1 eye

• Monocular cues• Relative height – we perceive objects higher in our field of vision as farther

away• Relative size - The larger of the two objects will appear closer and the

smaller will appear farther away.• Interposition - Results when objects overlap. The overlapping object appears

closer and the object being overlapped appears farther away• Linear perspective - Parallel lines come together, or converge, in the

distance. • Relative motion – As we move, objects that are stable appear to move. • Light and shadow – brighter objects seem closer, dimmer seem farther.

Perceptual Constancy

•Perceptual Constancy - perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change.

Perceptual ConstancyShape and Size Constancies

•Size constancy•Moon illusion•Ponzo illusion

Perceptual Set

•Perceptual set = a mental disposition to perceive one thing and not another.• Mental predisposition• Schemas• Nacirema