Sensation: The process of detecting physical energy from the environment and code that into neural signals

Perception: the way our brain selects, organizes, and interprets sensory information

Receptor cells stimulated by energy creates sensation

Sensory neurons carry information to the brain as coded signal

Transduction: the process of converting physical energy into an electrical charge

-the strength of stimuli affects how rapidly sensory neurons fire

—Each receptor cells is sensitive to a specific energy form

3.2 Sensory Thresholds

-We can’t detect a lot of the physical energy around us

-Different sensory thresholds in different species

Psychophysics: The study of the relationship between physical characteristics of stimuli and the sensory experiences that accompany them

Absolute threshold: Minimum amount of energy needed for someone to detect a stimulus 50% of the time

-Adults have a higher absolute threshold than kids generally

Difference threshold: the minimum difference between two stimuli needed to detect a difference at least 50% of the time

-This increases with the size of one stimuli (its relative)

Ernest Weber: Detectable differences are determined by ratios, not absolute numbers

-Or like percentages

-Size doesn’t matter, % difference does

Weber’s Law: the difference between two objects varies proportionally to the initial size of the stimulus

Signal detection theory: Differences to people’s responses to stimuli based on varying circumstances

-Our absolute thresholds and responses aren’t consistent over time

3.3

-We don’t sense all of the stimuli around us at all times

-There are times where we aren’t aware of stimuli, but our brain is interpreting it

Subliminal perception: sensation below our absolute threshold

Subliminal persuasion: using subliminal techniques to cause people to engage in behavior they wouldn’t typically do

-Ex: subliminal advertising, but results were made up

-Subliminally priming: presenting subliminally relevant information can lead to predicable behavior change

• most effective including goal-relevant cognitions

• Short lived effects

• You can protect yourself from subliminal persuasion

Sensory Adaption: when your senses are exposed to an unchanging stimulus and eventually stop registering the existence of the stimulus

Ex: the smell of your house

-Enables us to focus on changes in our environment

3.4 Visual Stimuli

-Vision is based on the availability of light

Wavelengths: the distance between the peak of each wave of energy (nanometers)

-We can only see a tiny bit of the electromagnetic spectrum

Humans see 400-700 nm

-Different wavelength = different color

-Different amplitude = different brightness

-Color’s purity (how much white light) = saturation

Cornea: first contact for light, the eye’s protective cover

Pupil: small hole in middle of eye

-Like a door

Iris: controls the pupil, dilates/constricts the pupil

-Each iris is unique

Lens: behind the pupil, changes shape to refract/focus light on the retina

(AKA visual accommodation)

Retina: Back of the eye, converts light stimuli into neural communication

-Retina sees objects upside down but our brain processes it as upright

Presbyopia: lens hardens and we can’t accommodate for distance

3.5 Eye function

-Retina is an extension of the brain

Rods and cones: photoreceptors in the first layer of the retina

Rods: Respond to varying degrees of light and dark, outside the fovea

Fovea: Depressed spot in the retina, center of your visual field

Cones: Receptors that allows us to see color, inside the fovea

-Work best in bright light

-Specialized for clarity

Optic nerve: carries neural messages from the eye to the brain. A one of the ganglion cells bundled together

Blind spot: Receptorless area at the back of the eye where the optic nerve is, images focused here aren’t seen in the visual field

-Each eye sees a portion of each visual field

Contralateral control

-Right half of each retina processes the left visual field

-Left half of retina processes right visual field

Two halves of the retina

-Temporal retina: outside half of the retina, close to your temple

-Nasal retina: Inside half of the retina, close to the nose

Right visual field: left temporal retina and right nasal retina process its information

-Each part of the retina leads to axons that converge and become the optic nerve, exiting through the blind spot

Optic chiasm: where a portion of both optic nerves cross over and continue to the brain

-Then, visual info does to thalamus for more processing, then sent to different spots

Feature detector neurons: Respond to specific types of features in the visual field

Simple cells: respond to a single feature

Complex cells: respond to two features of a stimulus

Hyper complex cells: respond to multiple features of a stimulus

-When neuron systems work together we perceive whole objects

-Some brain areas specialize in certain objects

Ex: visual cortex and faces

-We can process multiple things at the same time

Blindsight: experiencing blindness in part of a field of vision

3.6 Color Vision

-Nothing in our world inherently has color, we just perceive color

-Our perception of an object’s color isn’t absolute

-Depends partially on surrounding objects’ colors

-Most colors of objects are from reflected light

Subtractive color mixture: Some wavelengths of light are removed

-Ex: paint mixing

-Primary colors: cyan, yellow, magenta

Additive color mixture: all of the individually reflected wavelengths are added together and reflected when combined

-Ex: mixing light

-Primary colors: Red, green, blue

   -When all are mixed, you get white not black because white is a reflection off all of the wavelengths added together

Trichromatic theory of color vision: There are three different receptors (cones) that are each sensitive to varying wavelengths of light

-Light stimulates certain receptors in a particular way and that activity from the receptors is what gives our experience of color

We have three different cones:

-Short-wavelength cones: absorb up to 419-nm (blue cones)

-Medium-wavelength cones: absorbs up to 531-nm (green cones)

-Long-wavelength cones: absorbs up to 558-nm (red cones)

-To be truly colorblind, you would have no functioning cones, AKA monochromatism

-Dichromatism: Able to see some color, made from two primary colors usually

-More colorblind males than females

Opponent Process Theory

-Some color combinations we can’t see together (Ex: blueish yellow)

Afterimage: and image that remains within the visual field once the stimulus has been removed

Negative afterimage: opposite colors of what was originally presented

Opponent-process theory: there are three special receptors that work in an opposing manner

-Excitatory response to one color, inhibitory response to another

Microsaccades: small jerky movements in eye receptors that allow neurons to refocus

-Both theories are correct

3.7 The Ear

Sound wave: change in air pressure caused by air/fluid molecules colliding and moving apart

Frenquency: determines the pitch (Hz)

-Higher frequency, higher pitch

-Humans can hear sounds from 20-20,000 Hz (dolphins can hear 200,000 Hz)

Amplitude: determines volume (db)

-Anything over 85 can create hearing loss

Timbre: The purity and complexity of tone

Stereophonically: Hearing from two different sources

Sound shadow: a sound has to go through or around our head to reach the other ear

-As the sound travels around the head it weakens, tells us direction

Ear Anatomy

Outer ear: funnel for sound waves

Ear drum (tympanic membrane): vibrates from sound waves

Middle ear: has bones called the hammer, anvil, and stirrup that strike each other and pass the vibration to the oval window

Cochlea: in the inner ear, contains moving fluid that causes ripples in the basilar membrane

Basilar membrane: a stiff structural component of the cochlea, lined with thousands of hair cells containing cilia

Cilia: hair cell receptors that stimulate receptor cells and sends messages through the auditory nerve to the auditory cortex

-Volume of a sound affects the number of hair cells activated

-Too much noise can permanently damage hair cells, it destroys or fuses hair cells, causing impaired hearing

3.8 Hearing Theories

-Louder sounds carry/release more energy in the cochlea, moving more hair cells in the basilar membrane

Pitch is determined by location and rate the hair cells are moved

Place theory: Different pitches activate different sets of hair cells

Frequency theory: lower pitched sounds are perceived by the brain based on the neuron firing rate

-The problem with this is that we perceive pitches at a higher frequency than neurons can fire

Volley principle: neurons take turns firing, by combining forces they can create more power to the brain for interpretation

-Most researchers now agree that discerning pitch involves the position of neuronal activity and the temporal pattern of firing within and between neurons

-Place theory explains high frequency stimuli

-Frequency theory understands low frequency

-Volley principle is for low and moderate frequencies

Hearing Impairment

Sensorineural hearing loss: damage to the cochlea in the inner ear or from damage to the nerve pathways from the inner ear to the brain

-Usuallt from damage from outer and inner ear hair cell damage

-Most common type of hearing loss (aging process is associated with this, and loud music)

-Hearing aids: Amplifies a sound in the environment and the sound is processed normally

-Cochlear implants: small, complex technology that takes sounds from the external environment and converts them to electrical signals to be interpreted by the brain

-Bypasses the ear

Conductive hearing loss: Where the sound isn’t conducted properly through the outer or middle ear

-Experience a reduction in sound level

-Usually can be corrected through medication/surgery

Mixed hearing loss: a combination of sensorineural and conductive hearing loss. Can be damage to the outer, middle, and inner ear

-active Middle ear implants can help this

3.9 Smell and Taste

-Smell, taste, and touch are intertwined

-The back of the mouth cavity is connected to the nasal cavity

Smell

Olfaction: our ability to smell odors

-Molecules of a substance are carried through the air to the receptor cells at the top of our nasal cavities

-Smell can help us detect danger

-Some smells impact our somatosensory system

-There are nerve endings in our nose that are also sensitive to touch, temperature, and pain

-Our smell isn’t super acute

Olfactory receptor sites: large protein molecules on the olfactory neurons that bind to specific odorants

-Odor fits like a key in the receptor that is sensitive to it

-Transduced into electrical messages, go along the olfactory nerve to the brain

-Each odor triggers combinations of receptors

Olfactory cells regenerate through life

-The area of the brain that receives information from nasal receptors is connected to the limbic system

-Smell signals have direct links to the brain’s emotion and memory centers, so they can evoke memories

Taste

-We naturally avoid bitter foods to protect ourselves from poison

Taste buds: embedded in the tongue’s papillae

Papillae: little bumps on your tongue

Microvilli: tiny hairs at the tips of the taste receptor cells that generate a nerve impulse

-Interpreted by the brain as a particular taste

-Saliva dissolves the chemical substances in food so that they slip between the papillae and reach the taste buds

-Taste signals pass to the limbic system and the cerebral cortex

Five basic tastes: sweet, salty, sour, bitter, and umami

-We can also taste fat (oleogustus)

Taste receptor cells are on the tongue, mouth, and throat, some types more prevalent in certain areas

-Some people eating high fat high sugar food have intense taste sensations that make those foods unpleasant

-Some people have unusually high taste buds (aka super tasters)

-Most people have 20 taste buds, whereas a super taster can have 50 or more in a small area

-Each taste bud is associated with clusters of pain fibers

3.10 Body Senses

-Body senses are from a number of different senses

Touch

-We have a lot of receptor cells for touch

-Skin is the heaviest organ

-Touch can communicate things to others

-touch is part of the somatosensory system

-Different receptor cells in the skin layers process pressure, temperature, pain, etc and the density and sensitivity of those receptors vary

-Receptors respond relatively

Pain

-Pain encourages us to not do stuff again

-Pain is sensed by nociceptors, which detect multiple stimuli like harmful pressure, temp, etc

Hate control theory of pain: there are two different types of nerve fibers that relay information to our spinal cord- one thin fiber that carries the pain signal and another thicker fiber that transmits touch, pressure, and vibration

-Rubbing, squeezing, etc can stimulate larger nerve fibers and crowd out the nerve fibers communicating pain

Pain Management

Sensory-discriminative: the intensity, location, quality, and duration of pain

Affective-motivational: the negative experience of pain and desire to flee painful circumstances

Cognitive-evaluative dimension: one’s interpretation of the pain and the surrounding context (including cultural values)

-Pain can be acute or chronic

-Acute can be managed with VR(?)

-Chronic can be managed with medicine, psychological stuff, and alternative therapies

Complimentary and alternative medicine (CAM): medical practices not generally considered part of conventional/western medicine

Ex: meditation, herbs, massage, reiki

Body position and Movement

-Kinesthetic sense provides information about our positions and movements of our muscles/joints

-Proprioceptors: Specialized nerve endings that provide a constant stream of information from our body parts through our spinal cord into the parietal lobe cortex

-Vestibular sense: monitors the body’s position in space, determines body orientation

-Originates in the inner ear, hair cells send messages to the brain as they move to determine body rotation

-Vestibular sacs: connect the canals to the cochlea, contain tiny crystals stimulated by gravitation/movement

-The crystals bend the hair cells, help maintain balance

Motion sickness is caused by your vestibular sense detecting movement, but your visual field seeing that you’re stationary

Vestibular illusions: result from intense angular accelerations or decelerations, or by a sudden change in gravity

-Cause spatial disorientation

3.11 Perception theories

-Often involves a combination of gathering raw data and then an interpretation of that data

Bottom-up processing: the type of processing that starts with the raw data and send it to the brain for further processing

Top-down processing: Relies heavily on previous knowledge and experience to influence perceptions

-Most perception used both types of perception

3.12

Perceptual constancy: our perception of a stimulus remains the same even though some of its characteristics may have changed

Size constancy: distance is changing, size is not when someone is moving

-We also have color constancy and shape constancy

-Perceptual constancies develop over time and through experience

Perceptual set: a mental predisposition that influences the way we perceive things

Ex: a child draws a shitty horse picture and we perceive it as a horse

-Our tendency to view things in a specific way that is influenced by our motivations, expectations, emotions, attitudes, and culture

-Our perceptual sets can vary within the same stimulus

-Perceptual sets can also happen with hearing

Illusory contour: a visual illusion where lines are perceived without actually being present

-Activate regions in the visual cortex

3.13 Gestalt Principles

Gestalt: form or whole

-We naturally group objects together rather than a number of individual parts

Law of Pragnanz: we organize a stimulus into the simplest possible form

-People organize information according to proximity, similarity, closure, and continuity

3.14 Depth Perception

Depth perception: the ability to judge distances of objects and see them in three dimensions

-Our eyes see in 2D, brain constructs it into 3D

-Depth perception is party innate

Oculomotor cues: Specifically what is happening with and within your eyes when perceiving depth

Convergence: inward movement of our eyes while looking at something close up

Accommodation: eye lens changing shape

Monocular cues: Some cues that indicate depth/distance can be seen by one eye

Examples include:

Pictorial cues: information about depth communicated through 2D pictures

-Linear perspective and relative size

-Relative height and interposition

Motion parallax: the sense that objects moving further away are moving more slowly

-The more the image has to move between the eyes, the faster it has to move to be detected by both retinas

Binocular cues: a cue that involves both eyes

Retinal disparity: Slightly different images seen by the right and left eye due to the distance between the retinas

-The closer an object is, the larger the difference in the angles between what is seen by the right eye and left eye

3.15 Perceptual illusions

Perceptual illusions: the appearance of a stimulus is different than the actual nature of the evoking stimulus

Types:

Literal visual illusions: the illusion has already occurred before light enters the eye

Physiological illusions: excessive stimulation to the eyes or brain, creates a rebound type response (ex: afterimages)

Cognitive illusions: involve high-order thinking, and involve the most interaction between our sensory and perceptual systems (ex: impossible images)

-Muller-Lyer illusion: where lines appear shorter or longer but they’re actually the same length

• due to depth perception and size constancy