CHAPTER 3 - Sensation

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PSYCHOLOGYAN EXPLORATION

CHAPTER

Second Edition

Psychology: An Exploration, Second Edition Saundra K. Ciccarelli • J. Noland White

sensation and

perception

3




why study sensation and perception?Without sensations to tell us what is outside our ownmental world, we would live entirely in our own minds,

separate from one another and unable to find food orany other basics that sustain life. Sensations are themind’s window to the world that exists around us.Without perception, we would be unable to understandwhat all those sensations mean—perception is theprocess of interpreting the sensations we experience sothat we can act upon them.




Learning Objectives

• LO 3.1 Sensation and how it enters central nervous system

• LO 3.2 What is Light?

• LO 3.3 How eyes see and how eyes see color

• LO 3.4 What is sound?

•

LO 3.5 Hearing impairment and improvement • LO 3.6 How senses of taste and smell work

• LO 3.7 Sense of touch, pain, motion and balance

• LO 3.8 Perception and perceptual constancies

• LO 3.9 Gestalt principles of perception

•

LO 3.10 What is depth perception? • LO 3.11 How visual illusions work and other factors influence

perception




What is Sensation?

• Sensation is the stimulation of sensoryreceptors and the transmission ofsensory information to the brain.

• Process where various forms of outsidestimuli become neural signals in the

brain

LO 3.1 Sensation and the central nervous system




Sensory Thresholds

- Transduction:

Converting outside stimuli into neuralactivity

–Sensory receptors Specialized neurons

Stimulated by energy

•

Absolute Threshold–Lowest level of stimulation energy

needed to detect a stimulus 50 percentof the time





Table 3.1 Examples of Absolute Thresholds




Subliminal Sensation

• Subliminal stimuli

–Stimuli below the level of consciousawareness

Strong enough to activate the sensoryreceptors but not strong enough forconscious awareness





Habituation and Sensory Adaptation

• Habituation

–Lower centers of the brain filter sensorystimulation

– "Ignores" or prevents consciousattention to unchanging stimuli





Habituation and Sensory Adaptation

• Sensory adaptation

–Sensory receptor cells become lessresponsive unchanging stimulus

Microsaccades

–Constant movement of eyes

–Prevents sensory adaptation





Perceptual Aspects to Light

• Three aspects of the perception of light

–Brightness

Determined by amplitude of wave –

height of wave

Higher waves are bright, low wavesdimmer

LO 3.2 What is light






–Color (hue)

Determined by wavelength

Visible spectrum

–Portion of spectrum visible to the humaneye

Long wavelengths in red end, shorterwavelengths found at blue end







–Saturation

Purity of color

Less saturated contains larger variety ofwavelengths





Structure of the Eye

• Cornea

–Clear membrane, covers eye’s surface

–Protects eye

–Focuses most light coming into the eye

–Photoreactive Keratectomy (PRK)/Laser-Assisted keratomileusis

(LASIK) Vision-improving techniques

Small incisions in the cornea changefocus

LO 3.3 How eyes see and see color





• Aqueous humor

–Clear, watery fluid

–Continually replenished

–Supplies nourishment to the eye

• Pupil

–Hole where light from visual image

enters interior of the eye






• Iris

–Colored, round muscle

–Controls light via pupil size






• Lens

–Located behind the iris

–Suspended by muscles

–Finishes focusing process begun by thecornea






• Lens

–Visual accommodation

Change in the thickness of lens

Eye focuses on objects that are far awayor close

–Vitreous humor

Jelly-like fluid Nourishes the eye and gives it shape





Figure 3.2 Structure of the Eye Light enters the eye through the cornea and pupil. The iris controls the size of the pupil. From the pupil, lightpasses through the lens to the retina, where it is transformed into nerve impulses. The nerve impulses travel tothe brain along the optic nerve.





• Retina

–Final stop for light in the eye

–Contains 3 layers:

Ganglion cells

Bipolar cells





Figure 3.3 The Parts of the Retina (a) Light passes through ganglion and bipolar cells until it reaches and stimulates the rods and cones. Nerveimpulses from the rods and cones travel along a nerve pathway to the brain. (b) On the right of the figure is aphotomicrograph of the long, thin rods and the shorter, thicker cones; the rods outnumber the cones by a ratioof about 20 to 1.




Figure 3.3 (continued) The Parts of the Retina (c) The blind spot demonstration. Hold the book in front of you. Close your right eye and stare at the picture ofthe dog with your left eye. Slowly bring the book closer to your face. The picture of the cat will disappear at somepoint because the light from the picture of the cat is falling on your blind spot.




How the Eyes Work

• Dark adaptation

–Rods work best in low light

–Eyes adapt to low light after exposure to

bright light

• Light adaptation

–Cones adapt to increase in light rapidly

6 million cones in each eye





While this deer may see quite well when using its rods at night, the bright headlights of a car will activate thecones. The cones will adapt rather quickly, but it takes time for the deer’s pupil to contract, leaving the deerblinded by the light until then.




Theories of Color Vision

• Trichromatic theory

–Proposes three types of cones:

Red, blue, and green

–Mixing of direct light is additive;painting is subtractive

–Afterimage

Visual sensation persists for a brief timeafter original stimulus is removed

Colors contrast to those initially seen





Theories of Color Vision

• Opponent-process theory

–Proposes four primary colors with conespaired:

Red and green, blue and yellow

–Theory explains colors in afterimage





Figure 3.5 Color Afterimage Stare at the white dot in the center of this oddly colored flag for about 30 seconds. Now look at a white piece ofpaper or a white wall. Notice that the colors are now the normal, expected colors of the American flag. They arealso the primary colors that are opposites of the colors in the picture and provide evidence for the opponent-process theory of color vision.




Color Blindness

• Caused by defective cones in the retina

• Color deficient more accuratedescription





Color Blindness

• Three types:

–Monochrome colorblindness

Either have no cones or cones not

working

–Red-green colorblindness

Either red or the green cones are not

working–Sex-linked inheritance

Recessive inheritance pattern





Figure 3.6 The Ishihara Color Test Two facsimiles of the Ishihara Color Test. In the circle on the left, the number 5 should be easier to see for thosewith normal color vision, and on the right, the number 96. In both circles, individuals with color-deficient visionwill have difficulty identifying the numbers or may see nothing but a circle of dots.




Sound

• Sound waves are vibrations of themolecules of air that surround us.

–Hertz (Hz): measurement of frequency

• Has the same properties as lightwaves: wavelength, amplitude, andpurity

LO 3.4 What is sound?




Sound

• Wavelength

–Frequency or pitch (high, medium, orlow)

• Amplitude

–Volume (how soft or loud a sound is)

• Purity

–Timbre (richness in the tone of thesound)





Figure 3.7 Sound Waves and Decibels (a) A typical sound wave. The higher the wave, the louder the sound; the lower the wave, the softer the sound.If the waves are close together in time (high frequency), the pitch will be perceived as a high pitch. Waves thatare farther apart (low frequency) will be perceived as having a lower pitch.




Figure 3.7 (continued) Sound Waves and Decibels (b) Decibels of various stimuli. A decibel is a unit of measure for loudness. Psychologists study the effects thatnoise has on stress, learning, performance, aggression, and psychological and physical well-being.




Structure of the Ear

• Pinna

–Visible, external part of the ear

–Funnels sound waves

• Auditory canal

–Short tunnel runs to the eardrum(tympanic membrane)






• Eardrum

–Tightly covers opening into the middlepart of the ear

Sound waves cause eardrum to vibrate In turn, three tiny bones in the middleear vibrate

–Hammer, Anvil, Stirrup






• Cochlea

–Snail-shaped structure of the inner ear

–Filled with fluid

• Organ of Corti

–Rests in the basilar membrane

–Contains receptor cells for hearing






• Auditory nerve

–Bundle of axons from hair cells of innerear

–Receives neural message from organ ofCorti


Figure 3 8 The Structure of the Ear




Figure 3.8 The Structure of the Ear (a) This drawing shows the entire ear, beginning with the outer ear (pinna, ear canal, and eardrum). Thevestibular organ includes the semicircular canals and the otolith organs (inside the round structures just abovethe cochlea). (b) The middle ear. Sound waves entering through the ear canal cause the eardrum to vibrate,which causes each of the three bones of the middle ear to vibrate, amplifying the sound. The stirrup rests on theoval window, which transmits its vibration to the fluid in the inner ear.

Figure 3 8 (continued) The Structure of the Ear




Figure 3.8 (continued) The Structure of the Ear (c) The inner ear. Large spaces are filled with fluid (shown in purple) that vibrates as the oval window vibrates. Athin membrane suspended in this fluid is called the basilar membrane, which contains the organ of Corti, thestructure composed of the hairlike cells that send signals to the auditory cortex of the brain by way of theauditory nerve. (d) A close-up view of the basilar membrane (in dark pink) with the hair cells of the organ ofCorti (in lighter pink). Notice the axons (small green lines) leaving the hair cells to form the auditory nerve.

Figure 3 9 Cochlear Implant




Figure 3.9 Cochlear Implant (a) In a cochlear implant, a microphone implanted just behind the ear picks up sound from the surroundingenvironment. A speech processor, attached to the implant and worn outside the body, selects and arranges thesound picked up by the microphone. The implant itself is a transmitter and receiver, converting the signals fromthe speech processor into electrical impulses that are collected by the electrode array in the cochlea and thensent to the brain.




Figure 3.9 (continued) Cochlear Implant (b) This child is able to hear with the help of a cochlear implant. Hearing spoken language during the early yearsof a child’s life helps in the development of the child’s own speech.




Taste

• Taste buds

–Taste receptor cells in mouth

–Line the walls of papillae

• Gustation

–Sensation of a taste

–Chemical sense like neurotransmitters

LO 3.6 Senses of taste and smell




Taste

• Five Basic Tastes:

–Sweet

–Sour

–Salty

–Bitter

–Umami





Figure 3.10 The Tongue and Taste Buds—A Crosscut View of the Tongue (a) The right side of this drawing shows the nerves in the tongue’s deep tissue.




Figure 3.10 (continued) The Tongue and Taste Buds—A Crosscut View of the Tongue (b) The taste bud is located inside the papillae and is composed of small cells that send signals to the brain whenstimulated by molecules of food.




Figure 3.10 (continued) The Tongue and Taste Buds—A Crosscut View of the Tongue (c) Microphotograph of the surface of the tongue, showing two different sizes of papillae. The taste buds arelocated under the surface of the larger red papillae, whereas the smaller and more numerous papillae form atouch-sensitive rough surface that helps in chewing and moving food around the mouth.




Smell

• Olfaction

–Sense of smell

–Cilia

Small hair projecting into nasal cavity

Receptors for smell

At least 10 million receptors in each

cavity





Smell

• Olfaction

–Olfactory bulbs

Located just above the sinus cavity

Receive information from the olfactoryreceptor cells.





Figure 3.11 The Olfactory Receptors (a) A cross section of the nose and mouth. This drawing shows the nerve fibers inside the nasal cavity that carryinformation about smell directly to the olfactory bulb just under the frontal lobe of the brain (shown in green).




Figure 3.11 (continued) The Olfactory Receptors (b) A diagram of the cells in the nose that process smell. The olfactory bulb is on top. Notice the cilia, tinyhairlike cells that project into the nasal cavity. These are the receptors for the sense of smell.




Somesthetic Senses

• Consists of three systems

–Skin senses, kinesthetic senses, andvestibular senses

• Skin senses–Touch, pressure, temperature, and pain

–Sensory receptors located in the skin

Pacinian corpuscle–Responds to deep pressure





Somesthetic Senses

• Skin senses

–Sensory receptors located in the skin

Free Nerve endings

–Respond to changes in temperature,pressure, pain

LO 3.7 Sense of touch, pain, motion and balance




Somesthetic Senses: Pain

• Different types of pain:

–Visceral Pain

Pain in organs

–Somatic pain Pain sensations in skin, muscles,tendons, and joints

Carried on large nerve fibers





Somesthetic Senses: Pain

• Congenital analgesia and congenitalinsensitivity to pain with anhidrosis(CIPA)

– Inability to feel pain


Figure 3 12 Cross Section of the Skin and Its Receptors




Figure 3.12 Cross Section of the Skin and Its Receptors The skin is composed of several types of cells that process pain, pressure, and temperature. Some of these cellsare wrapped around the ends of the hairs on the skin and are sensitive to touch on the hair itself, whereas othersare located near the surface, and still others just under the top layer of tissue.




Somesthetic Senses

• Kinesthetic sense

–Sense provides informationabout body’s movement and

location in space–Proprioceptive receptors

Special receptors located inthe muscles, tendons, and joints





This tightrope-walking violinist is performing an amazing feat of coordination and muscular control. He must notonly use his vestibular organs to help maintain his balance, but also his kinesthetic sense to be aware of exactlywhere each foot is in relation to the rope.



Somesthetic Senses

• Vestibular sense

–Receptor structures in inner ear

–Sense of balance


CHAPTER 3 - Sensation

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