Stimulants
Excites neural activity and speeds up body functions
Puoils dilate, heart and breathing rates increase and blood sugar levels rise, causing a drop in appetite
Energy and self confidence rise
ie: caffeine, nicotine, amphetamines, cocaine, methamphetamines, ecstasy
amphetamines: drugs that stimulate neural activity, causing speeded up body functions and associated
energy and mood changes
people use them to feel alert, lose weight, boost mood or athletic performance
Nicotine
A stimulating and highly addictive psychoactive drug in tobacco
Smoking usually begins during early adolescence
As powerful and addictive as heroine and cocaine
Relaxes muscles and releases neurotransmitters that may reduce stress
Epinephrine and norepinephrine boost alertness and dopamine and opioids calm anxiety and reduce
sensitivity to pain
Suppresses appetite
Smoking correlates with higher rates of depression, chronic disabilities and divorce
Cocaine
Snorted, injected, or smoked
Enters the blood stream quickly and gives an instant euphoria
Followed by a crash which is caused by lack of serotonin, dopamine and norepinephrine
Heightens feelings of aggression
Leads to emotional distress, suspiciousness, convulsions, cardiac arrest, or respiratory failure
Methamphetamine
A powerfully addictive drug that stimulates the central nervous system with speeded up body functions
and associated energy and mood changes; over time, appears to reduce baseline dopamine levels
Triggers release of dopamine
After effects may be irritability, insomnia, hypertension, seizures, social isolation, depression and violent
outbursts
Over time, reduces amount of natural dopamine in the brain, and therefore causes permanently depressed
moods
Ecstasy
Both a stimulant and a mild hallucinogen
Triggers dopamine release
Releases serotonin and blocks its reuptake
Users experience high energy, emotional elevation, and feelings of intimacy with those around them
Has a dehydrating effect which can lead to overheating, high blood pressure and death
Can damage serotonin producing neurons, and lead to permanent depression
Suppresses immune system, impairs memory, slows thought, and disrupts sleep
Hallucinogens
Psychedelic drugs that distort perceptions and evoke sensory images in the absence of sensory input
LSD
Aka acid
Emotions vary from euphoria to detachment, to panic
Hallucinations begin with seeing shapes and patterns, then images of past experiences. At the peak, they
feel dream like and detached, and go into a panic and can harm themselves
Sensations are similar to the near death experience
Near Death experience: an altered state of consciousness reported after a close brush with death; often
similar to drip induced hallucinogens
Tunnel vision, bright lights, old memories, out of body sensations
Marijuana
Can be smoked or eaten
Contains THC
THC: the major active ingredient in marijuana; triggers a variety of effects, including mild hallucinations
Amplifies the senses
Relaxes, disinhibits, and produces a high
Impairs motor coordination. Perceptual skills and reaction time
THC stays in the body for a week or more
Regular users don’t need to take as much bc it’s still in their system
Usually just intensifies feelings
The more often you use it, the more likely that you’ll develop depression or anxiety
Interferes with memory formation
Can cause cancer, lung damage and pregnancy complications
We may have natural THC molecules, and cannabinoid receptors
THC molecules regulate pain
Influences on Drug Use
Biological influences
You’re more susceptible to alcohol dependence if your parents have a history of it
6 year old boys who were impulsive, energetic and fearless are likely to smoke, drink and use drugs as
teens
there are genes that are more common to people with predispositions to alcohol dependence
Psychological and Social Cultural Influences
Lack of sense of purpose
Significant stress or failure
Girls who have a history of depression, eating disorders, or abuse are at a high risk of substance addiction
Media exposure
Peer pressure
They’re the ones who throw the parties and supply the drugs
If one’s friends use drugs, it’s likely that one will too.
What one believes their friends are doing has an influence on one’s use of substances
Smokers tend to quit in clusters
We select those who are like us as friends
Culture
Sensation and Perception
 Sensation- the process by which our sensory receptors and nervous system receive and represent stimulus
energies form the environment
 Perception- the process of organizing and interpreting sensory info, enabling us to recognize meaningful
objects and events
 Bottom up processing- analysis that begins with the sensory receptors and works up to the brain’s
integration of sensory info
 Top down processing- information processing guided by higher level mental processes, as when we construct
perceptions drawing on our experience and expectations
Transduction
 Conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as
sights, sounds, and smells, into neural impulses our brain can interpret
 Psychophysics- the study of relationships between the physical characteristics of stimuli, such as their
intensity, and our psychological experience of them
Thresholds
 Absolute thresholds- the minimum stimulation needed to detect a particular stimulus 50% of the time
o
ie: pressure, sound, light, taste
 signal detection theory- a theory predicting how and when we detect the presence of a faint stimulus amid
background stimulation. Assumes there is no single absolute threshold and that detection depends partly on a
person’s experience, expectation, motivation, and alertness
o
why we tune out some stimuli and not others
 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.
o
Only when the stimulus triggers synchronized activity in several brain areas does it reach
consciousness
Difference Thresholds
 We need low absolute thresholds to detects important sensory stimuli
 We also need to be able to detect small differences in stimuli
o
ie: when tuning an instrument, or listening for your child’s voice among many
 difference threshold- the minimum difference between two stimuli required for detection 50% of the time
o
we experience the difference as a just noticeable difference
o
increases with the size of the stimulus

add 1 pound to a 10 pound weight and you will notice; add 1 pound to a 100 pound weight
and you will notice
 Weber’s Law- the principle that, to be perceived as different, two stimuli must differ by a given percentage
Sensory Adaptation
 Diminished sensitivity due to constant stimulation
o
Because our nerve cells fire less frequently
 Not the same for vision
o
Eyes are constantly moving, even if we’re not aware of it
 Sensory adaptation allows us to focus on informative stimuli rather than background noise
Perceptual Set
 A mental predisposition to perceive one thing and not another
 If you’re told to look to see something specific, you’ll see what you’re told to see.
 Can affect what we hear, taste, see
o
Choosing fries in a McDonald’s bag over the same fries in a plain white bag
 Our preexisting schemas influence our choices
Context Effects
 Perception is influenced by context
 ie: if you heard ‘eel is on the wagon’ your brain would work backward to fill in the first word as ‘wheel’
 the brain works backward to allow a later stimulus to determine how we perceive an earlier one
 context is influence by culture
o
different cultures have different experiences and predispositions
Emotion and Motivation
 listening to sad music can predispose people to perceive a sad meaning in spoken homophonic words like
mourning vs morning, die vs dye, pain vs pane
 a target looks farther away to those throwing a heavy object rather than a light one
 when angry, people more often perceive neutral objects as guns
 motives can direct our perception of vague images
o
ink blots
Vision
Our eyes receive light energy and transduce it into neural messages that our brain then processes into what we
consciously see.
Stimulus Input: Light Energy
 we see visible light, just one slice of the electromagnetic spectrum
 physical characteristics of light that help determine our sensory experience of them
light’s wavelength- the distance from the peak of one light or sound wave to the peak of the
o
next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses
of radio transmission.

Determines hue- the dimension of color that is determined by the wavelength of light;
what we know as the color names blue, green, etc
Intensity- the amount of energy in a light or sound wave, which we perceive as brightness or
o
loudness, as determined by the wave’s amplitude
The Eye
 Light enters the eye through the cornea
o
Cornea- protects the eye and bends light to provide focus
 then light passes through the pupil
o
pupil- the adjustable opening in the center of the eye through which light enters
 The iris dilates or restricts in response to light intensity and inner emotion
o
Iris- a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls
the size of the pupil
o
Each person’s iris’ are unique, like a fingerprint
 The lens focuses light rays into an image on the retina
o
Lens- the transparent structure behind the pupil that changes shape to help focus images on the
retina

o
Changes shape to focus on near or far objects in a process called accommodation
Retina- the light sensitive inner surface of the eye, containing the receptor rods and cones plus
layers of neurons that begin the processing of visual info

Converts light energy into neural impulses and sends them to the brain to form an image
The Retina
 When light travels to the back of the eye, it goes through rods and cones
o
Rods- retinal receptors that detect black, white, and gray; necessary for peripheral and twilight
vision, when cones don’t respond
o
Cones- retinal receptor cells that are concentrated near the center of the retina and that function in
daylight or in well lit conditions. The cones detect fine detail and give rise to color sensations
 Light in the rods and cones triggers chemical changes that spark neural signals
o
Neural signals activate bipolar cells
o
Bipolar cells activate ganglion cells
o
Ganglion cells form the optic nerve

Optic Nerve- the nerve that carries neural impulses from the eye to the brain to the thalamus
which distributes information
 Blind Spot- the point at which the optic nerve leaves the eye, creating blind spot because no receptor cells are
located there
 Cones
o
Cluster in and around the fovea

Fovea- the central focal point in the retina, around which the eye’s cones cluster

Some have a hotline to the brain

Use bipolar cells to send messages directly to the visual cortex

Enables the eyes to be able to detect fine details
o
Allow us to perceive color, but not in dim light
o
In the center of the retina
o
Share bipolar cells with other rods
o
No direct path to the brain
o
Responsible for peripheral vision
o
Several rods will funnel their energy into a single bipolar cell
o
Detect faint light
 Rods
 Usually takes eyes 20 minutes to adapt to a dark room
Visual Information Processing
 Processing begins in the retina
o
Encode and analyze sensory information
 Info then travels to bipolar cells, then to ganglion cells, then through the optic nerve to the brain
 Retinal cells are so sensitive that even pressure triggers them
o
The brain interprets their firing as light coming from the opposite side of where the pressure is
 Feature detectors- nerve cells in the brain that respond to specific features of the stimulus, such as shape,
angle, or movement
o
Special neurons in the occipital lobe
o
ie facial recognition

facial recognition is different than object recognition

based on fMRI’s, we can tell exactly what someone is looking at because feature detectors are
so specialized
 parallel processing- the processing of many aspects of a problem simultaneously; the brain’s natural mode of
information processing for many functions, including vision. Contrasts with the step by step processing of
most computers and conscious processing.
 to analyze an image, our brain divides the image into subgroups- color, motion, form, and depth- and works on
each level at the same time.
 To recognize a face, the brain separates out the parts of an image and sends the pieces to different areas, and to
be compared to stored knowledge
Complete Process of facial recognition:
Light waves reflect off the person’s face and travel into your eye. Receptor cells in the retina convert the light energy
into neural impulses that are sent to the brain. The brain processes the color, motion, form, and depth of the person
at the same time. It interprets the info based on stored images.
Feature detection:
Brain's detector cells
respond to specific
features- edges,
lines, angles
Parallel Processing:
Brain cell teams
process combined
information about
color, movement,
and depth
Recognition: Brain
interprets the
constructed image
based on information
from stored images
Retinal Processing:
receptor rods and
cones--> bipolar cells
--> ganglion cells
Image
Color Vision
 Some people are color deficient (blind)
o Usually male (sex linked)
 Young-Hemholtz trichromatic theory- 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 any color
 Color deficient people lack functioning red or green cones
o They have monochromatic or dichromatic, so they can’t distinguish between green and red
 Hering discovered that after staring at one color for a while, we see its opposing color
o Opponent process theory- opposing retinal processes (red-green, blue-yellow, white-black) enable
color vision.
 Some cells are stimulated by red and inhibited by green, and some are stimulated by green
and inhibited by red
o Red and green messages cannot travel to the thalamus at the same time, but red and blue can
 Afterimages- when we stare at green, we tire our green response. When we stare at white then, we see red
because only the red part of the green red pairing will fire
 Color processing occurs in 2 stages:
o The red, blue and green cones respond to different color stimuli (Young-Helmholtz theory)
o Their signals are processed by the opponent process cells (Hering)
Visual Organization
 Gestalt- an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information
into meaningful wholes
 The whole may exceed the sum of its parts
Form Perception
 To recognize a face, we need:
o Figure and Ground
 The organization of the visual field into objects that stand out from their surroundings
o Grouping
 Proximity- we group nearby figures together
 Continuity- we perceive smooth, continuous patterns rather than discontinuous ones
 Closure- we fill in gaps to create a complete, whole object
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- a laboratory device for testing depth perception in infants and young animals
o Gibson and Walk experiment
o Most infants resisted walking across the fake cliff, indicating that they have an innate sense of depth
 Binocular cues
o Depth clues, such as retinal disparity, that depend on the use of two eyes
 Retinal disparity- a binocular cue for perceiving depth: by comparing images from the retinas in the two eyes,
the brain computes distance- the greater the disparity between the two images, the closer the object
Monocular cues- depth cues available to either eye alone
o Relative height: we perceive objects higher in our field of vision as farther away
o Relative motion: as we move, stable objects appear to move. If you fixate on a point while moving,
objects beyond the point appear to move with you, while objects in front of the point seem to move
backwards
o Relative size: if we think two objects are the same size, we perceive the one with the smaller retinal
image as farther away
o Interposition: if one object partially blocks our view of another, we perceive it as closer
Linear perspective: parallel lines appear to meet in the distance
Light and shadow: shading produces a sense of depth based on our assumption that light comes from
above
Motion perception
 Our brains assume that shrinking objects are retreating and enlarging objects are approaching
 The brain perceives motion as a rapid series of slightly varying images
 Phi phenomenon- an illusion of movement created when two or more adjacent lights blink on and off in quick
succession
o
o
Perceptual Constancy
 Perceiving objects as unchanging even as illumination and retinal images change
o We recognize things regardless of changes in shape, size, brightness, color)
 Color and brightness constancies
o Color constancy- perceiving familiar objects as having consistent color, even if changing
illumination alters the wavelengths reflected by the object
 Color changes in relation to amount of light
 We perceive the same object as different colors under different illumination
 Color is relative to the objects around it too
o Brightness constancy
 We perceive an object as having a constant brightness even when illumination varies
 Shape and size constancies
o Shape constancy
 Objects sometimes seem to change shape based on our viewpoint of them
 We perceive the shape of familiar items the same even if the actual shape undergoes change
 Thanks to neurons that rapidly learn to associate different views of an object
o Size constancy
 We perceive familiar items as having a constant size, even when our distance from them
varies
 Knowing the distance of an object can help predict its size, and vice versa
Visual Interpretation
 Philosophers have debated whether perception is nature or nurture
o Kant believed we come equipped with the ability to process information
o Locke believed that through our experiences, we learn to perceive the world
Experience and visual perception
 Aspects of perception that are innate
o Sense colors
o Distinguish figure from ground
 Kittens and monkeys who gained vision after having goggles over their eyes could not distinguish shapes, but
could distinguish color and brightness
 visual restrictions later in life do no permanent harm
 there is a critical period for normal sensory and perceptual development
 nurture sculpts what nature has endowed
o ie: video games help coordination, speed, and tracking multiple objects
 early experiences last a lifetime
o use it soon or lose it
ESP

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
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extrasensory perception
the controversial claim that perception can occur apart from sensory input
telepathy- mind to mind communication
clairvoyance- perceiving remote events, such as a house on fire in another state
precognition- perceiving future events, such as an unexpected death in the next month
parapsychology- the study of paranormal phenomena including ESP and psychokenesis
Premonitions or pretensions?
 In recent years, ‘psychics’ have not been able to predict any big news, nor have they been correct about the
things they did predict
 The sheer volume of predictions increases the odds that some with be true, which they then report to the
media
 ‘psychics’ also make vague predictions so people have a perceptual set for when something vaguely similar
happens
 given the billions of events that happen every day, some coincidences are sure to happen
 parapsychology needs reproducible phenomena and a theory to explain it
 some psychologists think that some people have an evolutionary advantage that helps them precognitively
anticipate future dangers
o why can’t we predict casino outcomes then?
Perceptual Adaptation
 we can adjust to changes in our vision
o ie: getting new glasses
o even dramatic change
 perceptual adaption- in vision, the ability to adjust to an artificially displaced or even inverted visual field
 Stratton invented the first pair of glasses that switches left and right and up and down
Perception is the product of three sources
Sensation
Cognition
Emotion
Influences on Perception
Biological
Sensory analysis
Unlearned visual phenomena
Critical period for sensory development
Sensory system
Source
Vision
Light waves striking the eye
Hearing
Sound waves striking the outer ear
Touch
Pressure, warmth, cold on the skin
Taste
Chemical molecules in the mouth
Smell
Chemical molecules breathed in
through the nose
Any change in position of a body part,
interacting with vision
Movement of fluids in the inner ear
caused by head injury/body movement
Body position/
kinesthesis
Body movement/
vestibular sense
Psychological
Selective attention
Learned schemas
Gestalt principles
Context effects
Perceptual set
Social cultural
Cultural assumptions and expectations
receptors
Rods and cones in the retina
Cochlear hair cells in the inner ear
Skin receptors detect pressure, warmth, cold
Basic tongue receptors for sweet, sour, salty, bitter
and umami
Millions of receptors at top of nasal cavity
Kinesthesis sensors all over the body
Hair like receptors in the semicircular canals and
vestibular sacs
The Nonvisual Senses
Hearing
 Audition- the sense or act of hearing
 We can hear a wide range of frequencies, but the ones we hear best are ones of the human voice
 Good hearing was an evolutionary advantage (hunting)
o If our ears were any more sensitive, we would hear a constant hiss of the air molecules moving
 We are attuned to many variations in sounds
o We can recognize a friend on the phone the moment she says hi
The Stimulus Input: Sound waves
 Amplitude determines loudness
 Length determines pitch
o Frequency- the number of complete wavelengths that pass a point in a given time
o Pitch- a tone’s experienced highness or lowness’ depends on frequency



Long waves have low frequency and low pitch
Short waves have high frequency and high pitch
Measure sound in decibels
o
0 decibels is the threshold for absolute hearing
The Ear
 process of hearing:
o sound waves enter the outer ear
o outer ear channels the waves through the auditory canal to the eardrum, causing it to vibrate
o in the middle ear, three bones transmit the waves to the cochlea in the inner ear
 middle ear- the chamber between the eardrum and cochlea containing three tiny bones
(hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval
window
 cochlea- a coiled, bony, fluid filled tube in the inner ear; sound waves traveling through the
cochlear fluid trigger nerve impulses
 inner ear- the inner most part of the ear, containing the cochlea, semicircular canals, and
vestibular sacs
o the cochlea’s membrane vibrates, which causes motion in the fluid
o there’s a ripple in the hair cells, which trigger neural messages to the auditory nerve, which sends
info to the auditory cortex via the thalamus
 damage to the cochlea’s hair cells can cause:
o sensoirneural hearing loss- hearing loss caused by damage to the cochlea’s receptor cells or to the
auditory nerves; also called nerve deafness
 can be caused by disease
o conduction hearing loss- hearing loss cased by damage to the mechanical system that conducts
sound waves to the cochlea
o damage is usually linked with heredity, aging, and prolonged exposure to loud noise
 Ringing in the ears after exposure to loud noises indicates the hair cells have been damaged
 The only way to repair hearing for people with nerve deafness is a cochlear implant
o Cochlear implant- a device for converting sounds into electrical signals and stimulating the auditory
nerve through electrodes threaded into the cochlea
 can help children become orally proficient if installed early in childhood
 helps restore hearing in most adults
Perceiving Loudness
 The brain interprets loudness from the number of activated cells.
 If a hair cell loses sensitivity to soft sounds, it may still respond to loud sounds
o Explains why people with hearing loss can hear loud noises the same as people without
Perceiving Pitch
 How do we discriminate frequencies?
o Helmholtz’s place theory- in hearing, the theory that links the pitch we hear with the place where
the cochlea’s membrane is stimulated
 Different sound waves trigger stimulation at different places on the cochlea membrane
 The brain recognizes the specific place that is generating a neural signal
 Explains why we hear high pitched sounds, but not low pitched sounds
 Low pitches aren’t located in a specific place on the membrane
o frequency theory- the rate of the nerve impulses traveling up the auditory nerve matches the
frequency of a tone, thus enabling is to sense its pitch
 frequency of neural impulses= frequency of waves
 the only problem: one neuron cant fire faster than 1000 times per second, but we can hear
frequencies faster than 1000 waves per second
o Volley principle- neural cells can alternate firing
 Explains why we can hear high and low pitches
Locating Sounds
 The placement of our ears allows us to have 3D hearing
 Two ears are better than one because:
o A sound on the right will be more intense in the right ear
o sound enters the right ear sooner than in the left
The Other Senses
 seeing and hearing are given priority in the allocation of cortical tissue in the brain
 Touch
o Touch is essential to development
o Touch is a mix of senses for pressure, warmth, cold, and pain
 Stimulating nearby cold and hot spots produces the sensation of hot
 Repeated stroking of a pain spot produces an itching sensation
o Tickling yourself doesn’t produce as much activation as tickling from someone else
 The brain is smart enough to be most sensitive to unexpected stimulation
 Pain
o Pain is the body’s way of telling you something is wrong, draws you attention
o People who don’t feel pain die young because
 When they don’t feel discomfort that makes us shift position, their joints fail
 Without pain, effects of unchecked infections and injuries accumulate
o Women are more pain receptive than men
o Biological influences:
 Nociceptors- sensory receptors that detect hurtful temperatures, pressure, or chemicals
 Gate control theory- the spinal cord contains a neurological gate that blocks pain signals or
allows them to pass on to the brain. The gate is opened by the activity of pain signals traveling up
small nerve fibers and is closed by activity in larger fibers or by information coming from the
brain
 one way to fix chronic pain would be to stimulate gate closing activity in large neural
fibers
 the brain can control pain too
 when we are distracted from pain, and naturally painkilling endorphins are released, we
don’t feel pain as intensely
 some people have a gene that promotes the availability of endorphins which help soothe
pain
 sports injuries can go unnoticed for a while because their brains are so filled with
endorphins that the pain is masked
 phantom limb sensation: the brain creates pain when it misinterprets the spontaneous
central nervous system activity in the absence of normal sensory info
o you feel pain in places where there is no damage, or there might not even be a
limb there
o occurs in amputees and people born without limbs
o the brain assumes you have all of your limbs and body parts
o Psychological influences
 Distraction from pain is evident in athletes who play through the pain and focus on winning
 We are bad at remembering pain
 We only remember the pain’s peak and how much pain they felt at the end
 Lengthening the discomfort but lessening the intensity of the discomfort makes us remember less
pain overall
o Social Cultural influences
 We tend to perceive more pain when others also seem to be experiencing pain
 When feeling empathetic for another’s pain, we tend to mirror their brain’s pain
o Controlling Pain
 Can be treated both physically and psychologically
 Drugs, surgery, acupuncture, electrical stimulation, massage, exercise, hypnosis, relaxation
training, and though distraction
 Placebos can help reduce our experience of pain
 Distraction can activate pain inhibiting circuits and increase pain tolerance
 Pain is in the brain, so diverting the brain diverts the pain
Taste
 5 tastes: sweet, sour, salty, bitter, umami
o Umami: meaty taste, experienced as the flavor enhancer monosodium glutamate
Survival functions of Basic Tastes:

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Taste
Evolutionary Indication
Sweet
Energy source
Salty
Sodium essential to physiological processes
Sour
Potentially toxic acid
Bitter
Potential poisons
Umami
Proteins needed to grow and repair tissue
Explains fussy infants who are reluctant to eat bitter foods like spinach and Brussels sprouts
Taste is a chemical sense
Taste buds contain pores that catch food chemicals
Inside each pore is taste receptors hairs
Some receptors respond mostly to a certain taste
Taste receptor cells reproduce themselves every week or two, so if you burn your tongue, it doesn’t matter much
As you get older, the number of taste buds decreases as does taste sensitivity
o Older people enjoy strongly flavored foods
Those who lose their sense of taste say that food tastes like straw and is hard to swallow
Expectations can influence taste
More expensive wine tastes better, even if it’s the same wine
Sensory Interaction
 We get much of our taste experience from the smell of the food
 Smell can influence our perception of taste
 Sensory interaction- the principle that one sense may influence another, as when the smell of food influences its
taste
 Our brain blends sensory input to interpret stimuli
 Taste and touch
o Depending on texture, a chip can taste stale or fresh
Embodied Cognition
 Brain circuits that process our bodily sensations connect with brain circuits responsible for cognition
 Embodied cognition- the influence of bodily sensations, gestures, and other states on cognitive preferences and
judgments
Smell
 Smell is a chemical sense
 We smell tiny molecules of the substance
 Receptor cells in nasal cavity detect smells and send signals to the brain
 Some odors trigger a combination of receptors in patterns that are interpreted by the olfactory cortex
 We aren’t very good at describing smells
 Animals have many times more olfactory receptors than we do
o Dogs are used to track smells of people
 Preference of smells is learned
o Babies don’t come programmed to like the smell of their mothers
 We are very good at remembering familiar smells and their associated memories
 There is a hotline that runs between the receiving area for information from the nose, and the brain’s areas
associated with memory and emotion