1 Unit 4 Sensation & Perception. 2 Sensation and Perception Sensation – An early stage of...

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Unit 4Unit 4

Sensation & Perception

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Sensation and PerceptionSensation and Perception

Sensation – An early stage of perception in which neurons in a receptor create an internal pattern of nerve impulses that represent the conditions that stimulated it – either inside or outside the body

Perception –A process that makes sensory patterns meaningful and more elaborate

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The brain senses the world indirectly because the sense organs convert stimulation

into the language of the nervous system: neural

impulses

How Does StimulationHow Does StimulationBecome Sensation?Become Sensation?

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TransductionTransduction

Transduction – Transformation of one form of energy into another – especially the transformation of stimulus information into nerve impulses

Receptors –Specialized neurons that are activated by stimulation and transduce (convert) it into a nerve impulse

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TransductionTransduction

Sensory pathway – Bundles of neurons that carry information from the sense organs to the brain

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Sensory AdaptationSensory Adaptation

Sensory adaptation – Loss of responsiveness in receptor cells after stimulation has remained unchanged for a while

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ThresholdsThresholds

Absolute threshold – Amount of stimulation necessary for a stimulus to be detected,

Difference threshold – Smallest amount by which a stimulus can be changed and the difference be detected (also called just noticeable difference – JND)

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Approximate Perceptual Thresholds of the Approximate Perceptual Thresholds of the 5 senses5 senses

Light – A candle flame at 30 miles on a dark, clear night

Sound – The tick of a mechanical watch under quiet conditions at 20 feet

Taste - one teaspoon of sugar in 2 gallons of water

Smell - on drop of perfume diffused into the entire volume of a three bedroom apartment

Touch – The wing of a bee falling on your cheek from a distance of 1 centimeter.

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Weber’s law – The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low

Fechner’s law – S = k log RS = sensation

R = stimulus

k = constant that differs for each sensory modality

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Fechner’s law – Fechner’s law –

Also affects stimulus detection

States that an increase in the physical magnitude of a stimulus progressively produces smaller increases in perceived magnitude.

Now you try to explain that in ENGLISH!!

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Steven’s power law – S = kla

S = sensation

k = constant

l = stimulus intensity

a = a power exponent that depends on the sense being measured

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Steven’s Power LawSteven’s Power Law

More accurate than Fechner’s law

Covers a wider variety of stimuli.

Like pain and temperature

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Signal Detection TheorySignal Detection Theory

Signal detection theory – Perceptual judgment as combination of sensation and decision-making processes

Stimulus eventStimulus event

Neural activityNeural activity

Comparison with Comparison with personal standardpersonal standard

Action (or no action)Action (or no action)

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Subliminal PersuasionSubliminal Persuasion

Studies have found that subliminal words flashed briefly on a screen can “prime” a person’s later responses

No controlled research has ever shown that subliminal messages delivered to a mass audience can influence people’s buying habits

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Example of primingExample of priming

S N _ _ _ E L

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Example continuedExample continued

See if you had been previously primed by a brief presentation of the appropriate word, it would be more likely that you would have found the right answer, even though you weren’t aware of the priming stimulus.

Want to know what it was?....

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Here ya go!Here ya go!

S N O R K E L

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Homework assignmentHomework assignment

Tonight you need to read “what every skeptic should know about subliminal persuasion.”

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Today’s Mind Jog!!!!!!!!!!!Today’s Mind Jog!!!!!!!!!!!

How Are the Senses Alike? How Are They Different?

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The senses all operate in much the same way, but each extracts different information

and sends it to its own specialized processing region

in the brain

How Are the Senses Alike? How Are the Senses Alike? How Are They Different?How Are They Different?

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The Anatomy of Visual SensationThe Anatomy of Visual Sensation

Fovea – Area of sharpest vision in the retina

Retina – Light-sensitive layer at the back of the eyeball

Photoreceptors – Light-sensitive cells in the retina that convert light energy to neural impulses

Rods – Sensitive to dimlight but not colors

Cones – Sensitive tocolors but not dim light

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The Anatomy of Visual SensationThe Anatomy of Visual SensationOptic nerve –

Bundle of neurons that carries visual information from the retina to the brain

Blind spot – Point where the optic nerve exits the eye and where there are no photoreceptors

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Color –Psychological sensation derived from the wavelength of visible light – color, itself, is not a property of the external world

The Anatomy of Visual SensationThe Anatomy of Visual Sensation

Visual cortex –Part of the brain – the occipital cortex – where visual sensations are processed

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Transduction of Light in the RetinaTransduction of Light in the Retina

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RetinaRetina

located at the very back of the eyeball, is a thin film that contains cells that are extremely sensitive to light

light sensitive cells, called photoreceptors, begin the process of transduction by absorbing light waves

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Cones—concentrated in center of eye Cones—concentrated in center of eye (fovea)(fovea)

• approx. 6 million

• allow us to see in bright light, see fine spatial detail, and see different colors

• adapt quickly• one cone often synapses onto

only a single ganglion cell (increases visual acuity)

CONES!

COLOR!

CLARITY!

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Rods—concentrated in periphery Rods—concentrated in periphery

• approx. 120 million

• allow us to see in dim light and at night

• adapt slowly

• the axons of many rods synapse onto one ganglion cell (increases sensitivity to dim light)

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Optic nerveOptic nerve

• nerve impulses flow through the optic nerve as it exits from the back of the eye

• the exit point is the “blind spot”

• the optic nerves partially cross and pass through the thalamus

• the thalamus relays impulses to the back of the occipital lobe in the right and left hemisphere

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Primary visual cortexPrimary visual cortex

* the backs of the occipitals lobes is where primary visual cortex transforms nerve impulses into simple visual sensations

• Visual association areas

• the primary visual cortex sends simple visual sensations to neighboring association areas

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AfterimagesAfterimages

Afterimages – Sensations that linger after the stimulus is removed

In the following slide, fix your eyes on the dot in the center of the flag

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Look at the plus at the left for 30 secs then Look at the plus at the left for 30 secs then the rightthe right

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Blind SpotBlind SpotStare at the 3 and move back and forth Stare at the 3 and move back and forth

slowly until the sun disappearsslowly until the sun disappears

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If you look at the left (black/white) pattern you will probably notice that the vertical If you look at the left (black/white) pattern you will probably notice that the vertical pattern in the center appears to move relative to the horizontal pattern in the surround. pattern in the center appears to move relative to the horizontal pattern in the surround. This diagram was adapted from a design presented by a Japanese artist whose name This diagram was adapted from a design presented by a Japanese artist whose name is Ouchi. is Ouchi. If you see relative motion on the right pattern than you can conclude that the illusion If you see relative motion on the right pattern than you can conclude that the illusion also works with color patterns. also works with color patterns.

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Do you see the white diagonal lines coming Do you see the white diagonal lines coming from this? Really? They aren’t there.from this? Really? They aren’t there.

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Hermann Grid Illusion Hermann Grid Illusion

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Scintillating grid illusion Scintillating grid illusion

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More Information?More Information?

http://www.yorku.ca/eye/toc-sub.htm

This website has everything you need to really understand the eye!

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Neural Pathways in the Human Visual Neural Pathways in the Human Visual SystemSystem

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How the Visual System Creates ColorHow the Visual System Creates Color

Electromagnetic spectrum – Entire range of electromagnetic energy, including radio waves, X-rays, microwaves, and visible light

Visible spectrum – Tiny part of the electromagnetic spectrum to which our eyes are sensitive

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Brightness – Sensation caused by the intensity of light waves

How the Visual System Creates ColorHow the Visual System Creates Color

Color blindness – Vision disorder that prevents an individual from discriminating certain colors

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How the Visual System Creates How the Visual System Creates BrightnessBrightness

WavelengthWavelength

ColorColor

Intensity Intensity (amplitude)(amplitude)

BrightnessBrightness

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Ishihara Test for Color BlindnessIshihara Test for Color Blindness

What numbers do you see revealed in the patterns of dots?

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Ishihara Test for Color BlindnessIshihara Test for Color Blindness

What numbers do you see revealed in the patterns of dots?

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Color BlindnessColor BlindnessThe test to the left is simpler. The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.

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Connection/reflection!Connection/reflection!

So now that we have covered the eye in detail what differences do you think we will encounter with the next unit on the ear?

Any similarities?

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Hearing: If a Tree Falls in the Hearing: If a Tree Falls in the Forest...Forest...

The Physics of SoundFrequency –

Number of cycles completed by a wave in a given amount of time

Low Frequency High Frequency

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Hearing: If a Tree Falls in the Hearing: If a Tree Falls in the Forest...Forest...

The Physics of Sound

High Amplitude Low Amplitude

Amplitude – Physical strength of a wave

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How Sound Waves Become Auditory How Sound Waves Become Auditory SensationsSensations

Tympanic membrane –The eardrum

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Cochlea –Where sound waves are transduced

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Basilar membrane –Thin strip of tissue sensitive to vibrations

Cochlea

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Auditory nerve –Neural pathway connecting the ear and the brain

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Auditory cortex – Portion of the temporal lobe that processes sounds

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The Psychology of Pitch,The Psychology of Pitch,Loudness, and TimbreLoudness, and Timbre

Pitch – Sensory characteristic of sound produced by the frequency of the sound wave

Loudness – Sensory characteristic of sound produced by the amplitude (intensity) of the sound wave

Timbre – Quality of a sound wave that derives from the wave’s complexity

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DeafnessDeafness

Conduction deafness –An inability to hear resulting from damage to structures of the middle or inner ear

Nerve deafness –An inability to hear, linked to a deficit in the body’s ability to transmit impulses from the cochlea to the brain, usually involving the auditory nerve or higher auditory processing centers

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Position and MovementPosition and Movement

Vestibular sense –Sense of body orientation with respect to gravity

Kinesthetic sense –Sense of body position and movement of body parts relative to each other

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Test your Kinesthetic AwarenessTest your Kinesthetic AwarenessTest your current kinesthetic sense with the few simple exercises below. Evaluate how challenging each task is for you. Keep a slight bend in your knees during all activities.

1. Stand on both feet with proper posture (chest up, shoulders back, ears in line with shoulders) for 10 seconds. 2. Stand on one foot maintaining proper posture for 5 seconds. 3. Stand on both feet maintaining proper posture with your eyes closed for 5 seconds. 4. Stand on one foot maintaining proper posture with your eyes closed for 5 seconds

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Test your Kinesthetic AwarenessTest your Kinesthetic AwarenessIf you were able to complete all four tasks with

ease, you have pretty good kinesthetic awareness. If it was difficult just to maintain proper posture while standing on two feet, you may have some training to do. For most people, the tasks listed above will become increasingly more challenging because the exercises become more novel from one to four. While performing the tasks on one leg and/or with your eyes closed, you may have felt your ankles, knees or even hips wobble back and forth, from side to side or both. Your body was trying to stabilize itself and become aware of its positioning in space.

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HEARING DEMONSTRATIONHEARING DEMONSTRATION

We need a volunteer to be blindfolded and to sit in the middle of the room!

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SmellSmell

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Taste buds –Receptors for taste (primarily on the upper side of the tongue)

TasteTaste

Gustation – The sense of taste

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