Unit IV Sensation | Perceptionmrsyopsychology.weebly.com/uploads/9/3/1/7/9317682/unit... · 2018-11-07 · I.Basic Principles of Sensation and Perception Objectives: Contrast sensation

Unit IV Sensation | Perception

Module 16: Basic Principles of Sensation and PerceptionModule 17: Influences of PerceptionModule 18: VisionModule 19: Visual Organization and InterpretationModule 20: HearingModule 21: The Other Senses

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I.Basic Principles of Sensation and Perception

Objectives:

✤ Contrast sensation and perception, and explain the difference between bottom-up and top-down processing.

✤ Discuss how much information we can consciously attend to at once.

✤ Identify the three steps that are basic to all our sensory systems.

✤ Distinguish between absolute and difference thresholds, and discuss whether we can sense and be affected by stimuli below the absolute threshold.

✤ Explain the function of sensory adaptation.2

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Sensation

Process by which our sensory receptors and nervous systems 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.

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Bottom-up processing

Taking sensory information and works up to higher level processing.

✤ EX: Sensation

✤ What am I seeing?

✤ (eyes see the bowl and contents, nose smells chocolate, pickles, and hot sauce, stomach churns, face grimaces, head turns away) DETECT through SENSES

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Top-down processing

Constructs perceptions from the sensory input by drawing on our OWN experiences and expectations

✤ EX: Perception

✤ Guided by higher level mental processes

INTERPRET what our senses detectIs that something I’ve seen before?

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“Meanwhile in a silent, cushioned, inner world, our brain floats in utter darkness. By itself, it sees nothing. It hears nothing. It feels nothing. So how

does the world out there get it?”

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Is this you?

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Attention is POWERFULLY selective!

Selective Attention:

Focusing of conscious awareness on a particular stimulus

✤ Example: Cocktail Party Effect

✤ Ability to attend to only ONE voice among many (while detecting your own name)

✤ fMRI scans show that multi-tasking distracts from brain’s resources

✤ Our attention shifts back & forth while multi-tasking

http://tywkiwdbi.blogspot.com/2013/01/what-­‐do-­‐you-­‐notice-­‐about-­‐these-­‐photos.html11

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Selective InattentionInattentional blindness:

Failing to see visible objects when our attention is directed elsewhere

✤ Our conscious mind is in one place at a time

✤ https://www.youtube.com/watch?v=tXFsH__PIRA

Change blindness:

Failing to notice change in the environment

✤ A form of inattentional blindness

✤ Magicians manipulate our selective attention- “Out of sight, out of mind”

✤ http://www.msnbc.msn.com/id/38154937/ns/dateline_nbc-the_hansen_files_with_chris_hansen/

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Choice blindness?

What three steps are basic to all our sensory systems?

Transduction:

conversion of one form of energy so that our brain can use/make sense of it.

“R.T.D”

✤ RECEIVE sensory stimulation, often using specialized receptor cells.

✤ TRANSFORM that stimulation into neural impulses.

✤ DELIVER the neural information to our brain. 14

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Absolute Threshold

The minimum stimulation necessary to detect a particular light, sound, pressure, taste, or odor 50% of the time

✤ Can be tested by exposing each ear to varying sound levels

Single detection theory

A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise).

✤ Detecting a weak signal, depends not only on the signal’s strength but also our psychological state (our experience, expectations, motivation, and alertness)

✤ Seek to understand why people respond differently to the same stimuli

✤ Examples: teachers and cell phones, lonely speed daters being unselective, parents of newborn hearing faint whimper

“Faint stimuli”

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Subliminal

Stimuli you cannot detect 50% of the time (below your absolute threshold)

✤ Under certain conditions, you can be affected by stimuli so weak that you don’t consciously notice them

✤ Imperceptibly brief stimulus triggers weak response in brain. Only detected by brain scans.

Priming

The activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response

✤ Experiment: image or word is quickly flashed, then replaced by a masking stimulus that interrupts the brain’s processing before conscious perception

Much of our information processing occurs automatically, out of sight, off the radar of our conscious mind. DUAL PROCESSING!

“The heart has its reasons which reason does not

know.”

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Difference Threshold

Minimum difference a person can detect between 2 stimuli 50% of the time (just noticeable difference- jnd)

✤ Weber’s law

The principle that to be perceived as different, two stimuli must differ by a constant minimum percentage; not a constant amount

Examples: Quarters, envelopes, & shoes. 20

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JND? 21

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Sensory Adaptation

Diminished sensitivity as a consequence of constant stimulation

✤ When we are constantly exposed to a stimulus that does not change, we become less aware of it because our nerve cells fire less frequently

✤ Influences our perceptions of emotions (see Fig.16.9 p.160)

✤ Examples: watch on wrist, smelly moth ball home, stinkies

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We perceive the world not exactly as it is, but as it is useful for us to perceive it.

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II: Influences on Perception

Objectives:

✤ Explain how our expectations, contexts, emotions, and motivation influence our perception.

✤ List the claims of ESP, and discuss the conclusions of most research psychologists after putting these claims to the test.

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✤ Describe what you saw. Keep in mind, that this is a police investigation and that your testimony can be used in a court of law.

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1 . P a s t e x p e r i e n c e s“ S t a r s p a n g l e d _ _ _ _ _ _ _ _ _ _ _ _ _ _ ”

2 . M o o d s , A t t i t u d e s , a n d V a l u e s

H a v i n g a b a d d a y a n d “ t h i n g s ” s e e m t o s n o w b a l l

3 . N e e d sI f y o u ’ r e h u n g r y , y o u t h i n k a b o u t …

4. What the group believes

W e h a v e a t e n d e n c y t o , “ g o a l o n g w i t h t h e c r o w d . ”

S E E I N G – H E A R I N G – T O U C H I N G – T A S T I N G – S M E L L I N G

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Perceptual Seta mental predisposition to perceive one thing and not the other (top-down processing)

✤ Can influence what we hear, taste, feel, and see

✤ Through experiences we form concepts, or schemas that organize and allow us to interpret unfamiliar information

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Perceptual Set

✤ Examples:

✤ Pilot: Cheer up “Gear Up”

✤ Vinegar in beer- tastes better. Until…..

✤ Stereotypes about gender. Newborn David or Diana? Without color cues blue or pink- difficult identifying gender.

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Context Effectsa stimulus may trigger radically different perceptions (in others), partly because of our differing perceptual set, but also because of the immediate context.

✤ The brain can work backward in time to allow a later stimulus to determine how we perceive an earlier one. (top-down processing)

✤ “eel is on the wagon” perceive the first word as wheel

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Emotion and Motivation

✤ Our emotional context, as well as our motivation, can create expectations and color our interpretation of events and behaviors

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ESP

The controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition

Parapsychology

The study of paranormal phenomena, including ESP and psychokinesis

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Testable forms of ESP

Telepathy

Mind-to-mind communication

Clairvoyance

Perceiving remote events, such as a house on fire in another state

Precognition

Perceiving future events, such as a unexpected death in the next month

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Premonitions or Pretensions?

Can psychics see the future? Can psychics aid police in identifying locations of dead bodies? What about psychic predictions of the famous Nostradamus?

✤ The answers to these questions are NO! Nostradamus’ predictions are “retrofitted” to events that took place after his predictions.

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Putting ESP to Experimental Test

In an experiment with 28,000 indivduals, Wiseman attempted to prove whether or not one can psychically influence or predict a coin toss. People were able to correctly influence or predict a coin toss 49.8% of the time.

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Claims to ESP

Skeptics argue:

1. to believe in ESP you must believe the brain is capable of perceiving with out sensory input

2. researchers have been unable to replicate ESP Phenomena under controlled conditions

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III: Vision

Objectives:

✤ Describe the characteristics of visible light, and explain the process by which the eye transforms light energy into neural.

✤ Describe how the eye and the brain process visual information.

✤ Discuss the theories that help us understand color vision.

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The Wavelengths we see

What we see as light is only a tiny slice of a wide spectrum of electromagnetic energy, which ranges from gamma rays as short as the diameter of an atom to radio waves over a mile long. The wavelengths visible to the human eye (below) extend from the shorter waves of blue-violet light to the longer waves of red light. 38

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Light Energy

Two physical characteristics of light help determine our sensory experience of them.

✤ Wavelength

The distance from one wave peak to the next determines its perceived hue (the color we experience)

✤ Intensity (amplitude)

The amount of energy in light waves determined by a wave’s amplitude (height) influences brightness

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(a) Waves vary in wavelength (the distance between successive peaks). Frequency, the number of complete wavelengths that can pass a point in a given time, depends on the wavelength. The shorter the wavelength, the higher the frequency. Wavelength determines the perceived color of light (and also the pitch of sound). (b) Waves also vary in amplitude (the height from peak to trough). Wave amplitude determines the brightness of colors (and also the loudness of sounds). https://www.youtube.com/watch?v=l8_fZPHasdo 41

Light rays reflected from a candle pass through the cornea, pupil, and lens. The curvature and thickness of the lens change to bring nearby or distant objects into focus on the retina. Rays from the top of the

candle strike the bottom of the retina, and those from the left side of the candle strike the right side of the retina. The candle’s image on the retina thus appears upside down and reversed. 42

Retinal Processing

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Part of EYE Function

Cornea Light enters the eye through the cornea. Protects the eye and bends light to provide focus.

Pupil Light then passes through the pupil, a small adjustable opening

Iris (very distinctive)A ring of muscle tissue that forms the colored portion of the eye around the pupil and constricts in response to light intensity and even inner emotions

LensThe transparent structure behind the pupil that changes shape to help focus images on the retina. The lens focuses the rays by changing its curvature in a process called accommodation.

RetinaThe light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

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The Lens: Accommodation (adjustments)

The process by which the eye’s lens changes shape to help focus near or far objects on the retina.

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Nearsighted

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Farsighted

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RETINA Function

Photoreceptors - Rods and Cones- Retina cells that respond to light

Rods - Most sensitive to light and dark changes- Retinal receptors that detect black, white, and gray- Rods are more numerous than cones in periphery of retina

Cones

- Not sensitive to light; most sensitive to (green, red, blue)- Signals from cones sent to brain which then translates these messages into the

perception of color- Only works in bright light- Color vision, fine details- “Color blind” does not have a particular type of cone in the retina or the cone

may be weak

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Optic Nerve - The nerve that carries neural impulses from the eye to the brain

Fovea

- Central region of retina = most clear vision- No rods; only cones (packed together closer)- Blood vessels and nerve fibers go around fovea providing a direct path to the

photoreceptors

Blind Spot

- This is where the optic nerves come together and exit the eye on the way to the brain

- Part of the retina that does not contain photoreceptors- Any image that fills on this region you will not see

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Receptors in the Human Eye: Rod-Shaped Rods and Cone Shaped Cones

Cones Rods

Number 6 million 120 million

Location in retina Center Periphery

Sensitivity in dim light Low High

Color Sensitivity High Low

Detail sensitivity High Low

When you enter a darkened theater or turn off the light at night, your eyes adapt. Your pupils dilate to allow more light to reach your retina, but it

takes 20 minutes or more before your eyes fully adapt.52

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How do the eye and the brain process visual information?

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after processing by your retina’s

nearly 130 million receptor rods and cones

info travels to bipolar

cells

then to ganglion

cells

through axons making up the optic nerve to

thalamus

where the axons synapse with

neurons that run to the visual

cortex

in the occipital lobe at the back

of your brain

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Feature Detection

Nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement

Specialized neurons in the occipital lobe’s visual cortex receive information form individual ganglion cells in the retina

These cells pass this information to other cortical areas, where team of cells (supercell clusters) respond to more complex patterns

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https://www.youtube.com/watch?v=y_l4kQ5wjiw

Nerve  cells  in  the  visual  cortex  respond  to  specific  features,  such  as  edges,  angles,  and  movement.  

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Parallel ProcessingOur brain computes multiple things at once; a scene is analyzed the brain divides it into subdimensions— motion, form, depth, color—-and works on each aspect simultaneously

Other neural teams integrate the results, comparing them with stored information and enabling perception

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Visual Information Processing

SceneRetinal processing:

Receptor rods and cones —> bipolar cells

—> ganglion cells

Feature Detection: Brain’s detector cells respond to

specific features — edges, lines, and angles

Parallel processing: Brain cell teams

process combined information about

motion, form, depth, color

Recognition: Brain interprets the constructed image based on information from stored images

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What theories help us understand color vision?

✤ Young-Helmholtz trichromatic theory

The theory that the retina contains three different color receptors—one most sensitive to red, one to green, one to blue, which when stimulated in combination, can produce the perception of any color

Most people with color-deficient vision are not actually “color blind.” They simply lack function red or green sensitive cones or sometimes both. (monochromatic or dichromatic)

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Ishihara Test

http://www.webexhibits.org/causesofcolor/2.html  62

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✤ Opponent-process theory

The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green

If there is a red and green marble competing going through a narrow tube both cannot travel at once (they are opponents)

However red and blue travel in separate channels, so we can see a reddish-blue magenta

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Can be see when we look at after images!

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Cones

Retinal Ganglion Cells

✤ Opponent-process theory

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Opponent Process- Afterimage EffectThey are caused by fatigued cells in the retina responding to light.

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