Unit 6 - Sensation and Perception

Sensation

Definition: process through which sensory receptors in the body receive information from the environment

• Ex: kid smells bad next to you

• Hearing, seeing, smelling, touching

• Sensory receptors - the primary part of the body responsible for taking information in

Thresholds

Definition: the point at which we become aware of the stimulation from taking in sensations

• Absolute Threshold - the minimum stimulation needed for us to acknowledge that we have detected a stimulus in the environment

  • Ex: As the light dimmer is slowly turned to fully on, this is the point in which you notice it

  • Signal Detection Theory - method of predicting the point at which one would be able to detect a stimulus

    • Motivation, exhaustion, expectations, how much experience you have

    • Certain factors determine when you notice a stimulus

    • Ex: If you’re tired, you are probably not gonna be able to notice things as well due to exhaustion

• Difference threshold (noticeable difference/JND) - minimum difference between two stimuli that is required for us to be able to tell the difference between the two

  • Ex: when comparing red colors of paint to be used to paint a chair, this is the point at which we notice the change from one red color to the next shade of red

• Subliminal stimulation - stimulation that is slightly below absolute threshold

  • Ex: frame of popcorn in the middle of a movie

    • Mental trick to get popcorn in someone’s head pulled by old movie theaters

  • Not consciously aware of it

  • Weber’s Law - idea that to perceive the difference between two stimuli, they must differ by a constant percentage, not a constant amount

    • Simply means that it is easier to determine the difference between two stimuli by calculating the percentage

    • Ex: in the case of the red chairs, one might say that red #1 is 10% darker than red #2

Transduction and Sensory Adaptation

• When sensory information that's been received through sensory receptors goes up to the brain, it must be converted into an electrical signal that can travel via the neurons

  • Ex: the brain does not hear voices, it processes electrical messages that represents a voice that the ears hear

• Transduction - process of changing these external sensations into electrical messages

• Sensory Adaptation - the idea that constant stimulation in the environment fails to be sensed after an extended period of time

  • Ex: when you put on a bandage, at first, you notice it a lot, but after a while, you fail to notice it

Selective Attention

Definition: when focus is directed towards one particular thing

• Other things might get tuned out

• Needed in order to focus on things

  • Otherwise we would try to focus on everything at once

• People with ADD (Attention Deficit Disorder) struggle with selective attention

• Cocktail Party Effect - when at a party, an individual only hears the people he is talking to and focused on, not all of the other people at the party

• Inattentional blindness - when people fail to see things in the environment because they are so focused on a particular stimulus in the environment

  • Ex: gorilla study where people had to count number of passes in basketball and they never see the gorilla

• Change blindness - when people fail to notice changes that apply to aspects of the environment to which they are not paying attention

  • Ex: person swap studies where two people are talking, and somehow, one changes with another person and they don't even notice

Perception

Definition: the way in which the brain interprets these sensations presented by the sensory receptors

• Brain interprets what these things mean and tells it to the rest of the body

Bottom-Up Processing

Definition: when we take sensory information and it goes to the brain to be processed/interpreted

• Ex: a strange sound has not been heard before, and it goes to the brain to be interpreted in an attempt to determine what is making the sound

• Happens ALL the time

Top-Down Processing

Definition: when prior knowledge and expectations influence the way that your brain processes what comes in through your senses

• Ex: you hear a nearby shot, and after the message gets to the brain, you drop to the ground because you are in the middle of a store

• Political cartoons are another example due to the pre-existing political biases

Vision

Light Energy

• Light travels in waves, so aspects of color can be determined based on the qualities of a particular wave of light

• Object that is a certain color will reflect a certain wavelength of light from its surface based on the electrons in the atoms of that substance

• Our eyes perceive that color based on the light wavelength

• Hue - actual color of the object

  • Determined by the wavelength of light

    • Definition: distance from crest to crest

  • Tighter wavelengths are blueish

  • Longer wavelengths are reddish

  • Taller waves are brighter

  • Shorter waves are duller

Structure of the Eye

• Cornea - clear structure over the front of the eye that serves to protect the eye

• Iris - colored muscle of the eye

  • Expands in dark environments to allow more light into the eye

  • Constricts in bright environments to limit the amount of light that comes in

• Pupil - the hole in the center of the iris that allows light into the eye

• Lens - focuses the light onto the back wall of the eye (retina) as light enters

  • Behind the pupil

  • Accommodation - process by which the lens expands and shrinks to focus light

    • For objects that are close and are far

Retina

Definition: back of the eye where the sensory receptors (photoreceptors) are located

• Where transduction occurs

• Lens projects light onto the retina after the light has passed through the cornea, iris, and pupil

• Made up of photoreceptors

  • Definition: transduce, or convert, visual information in the form of light energy into electrical messages that will be sent to the brain

  • Rods and cones are where visual image is first interpreted

  • Rods - photoreceptors that can detect black and white

    • Located throughout the retina, including the periphery for peripheral vision, where the cones are not found

    • More spread out

  • Cones - photoreceptors that can detect fine detail and color

    • Located in the center of the retina

    • Since they are not located in the periphery, people can not identify colors in their peripheral

    • Fovea - area where the cones cluster in the center of the retina

    • Start process of color processing

• Bipolar Cells - where light goes after being transduced by the photoreceptors

  • Location where transduction is completed

  • In front of the photoreceptors

  • Send a message to the Ganglion cells

    • Definition: merge the message into the optic nerve so that it can be sent to the brain

• Optic Nerve - exits the eye, goes into the brain, and enables the transduced message to enter the brain for processing

  • No photoreceptors where the optic nerve leaves the eye

  • Blind Spot - tiny area in the back of your eye where no image can be sensed

    • Basically where the optic nerves are going to exit

    • People are often not aware of the blind spot because their eyes are constantly moving, so nothing is in their blind spot for long

    • Can be different places in each eye, so they can makeup for what is being missed with the other

Visual Processing

• Before processing, visual information must be relayed by the thalamus (relay center, part where everything is told where to go) to the occipital lobe

  • Thalamus receives a majority of the messages when they are sent to the brain

• Occipital Lobe - cells engage in feature detection

  • Definition: recognition of specific features, or elements of an image

  • Ex: movement, lines, corners, angles, edges

• Parallel Processing - simultaneous processing of color, depth, movement, and form of a processed image

Color Processing

There are two widely accepted theories for how the cones process color within the eye.

• Cones begin the process of seeing color

Trichromatic Theory

Definition: there are three types of cones to process three primary colors of light: green, blue, and red

• All other colors are seen through various combinations of the three primarily colors

• Also referred to as the Young-Helmholtz Theory

  • Based on the work of Thomas Young and Hermann von Helmholtz

Opponent-Process Theory

Definition: sensory receptors come in opposing pairs (their dramatic opposites)

• Red-green

• Blue-yellow

• Black-white

• When one color is stimulated, the other color is inhibited

  • If you stare at a color for a while and then look away, you will see its opponent color instead

Hearing

Sound Waves

• Audition - the processing of sounds

• Sound travels in waves

  • Aspects of sound can be determined based on the qualities of a particular wave of sound

• Pitch (Frequency) - refers to how high or low a sound is

  • Determined by the actual length wavelength of a sound

  • Tighter waves are higher pitch sounds

  • Spread-out waves are lower pitch sounds

• Intensity (Volume) - loudness of a sound

  • Determined by the amplitude of a sound wave

  • Tall waves are louder sounds

  • Shorter waves are quieter sounds

• Decibels - measure of how loud a sound is

  • Abbreviation - dB

  • Ex: a normal conversation would be about 60 dB, a jet taking off would be about 110 dB

  • Loud sounds over a period of time can cause hearing damage

  • Rock Band concert is louder than a jet plane or normal conversation

Structure of the Ear

• Outer Ear - collects sound waves and sends down the auditory canal

  • Auditory is the traveling canal

• Ear drum (tympanic membrane) - when the sound waves hit the eardrum, waves are turned into vibrations

  • Contained within the middle ear

• From the ear drum, the vibrations hit the three middle ear bones: the hammer, anvil, stirrup

• After the bones, the vibrations enter the cochlea, which is a fluid-filled part of the inner ear

  • Looks like a snail shell

  • Where transduction occurs

• Inside the cochlea is the basilar membrane with hair cells that transduce the sound

• From the cochlea, the auditory nerve takes the message to the brain to be deciphered

• Sound localization - we have two ears that hear sound from one side or the other

  • Ex: if a sound reaches the left ear first, we know it’s because it comes from the left side

Perception

• After transduction of sound, the brain must process the information to be understood

  • Also how the brain deciphers it

• Extending ear by a pipe would impact how sound is processed in the body

Two basic theories:

Place Theory

Pitch is detected based on the specific location in the cochlea where hair cells are stimulated.

Frequency Theory

Pitch is detected based on the rate at which the messages are being sent to the brain.

• Transacted sound travels by the auditory nerve

• Thalamus relays auditory information to the temporal lobe for processing

Deafness

• Two most common ways are birth and loss from age

Conduction Hearing Loss (Mechanical)

When there is a physiological damage to the mechanical part of the outer or middle ear

• Ex: damage to the ear drum or middle ear bones (ossicles)

• Can often be fixed with a hearing aid

Sensorineural Hearing Loss (Nerve Deafness)

Occurs inside the cochlea, where transduction occurs

• Because transduction cannot occur naturally, a cochlear implant can be used to transduce sound for the individual

  • Replaces the cochlear

• More commonly a problem the individual has from birth

• More serious than conduction hearing loss

Touch

• 4 basic skin sensation identifiers**: pressure, warmth, coldness, pain**

  • All other touch sensations are related to one or more of these four

  • Pressure is the only one that is known to have actual receptors to carry messages to the brain

    • Everything else is most likely a variation of pressure

• Congenital Insensivity to Pain with Anhidrosis (CIPA) - disorder in which people do not sense pain

  • They do not realize when they have been hurt

• Kinesthesis - body’s sense of where it is located in space and its position in space

  • Sensation of movement or strain in the muscles

• Vestibular Sense - controls equilibirium and balance

  • When the head moves, the body follows

• Pareital lobe is the closest to touch perception

Taste

Five Basic Taste Sensations:

• Sweet

  • Ex: candy

• Sour

  • Ex: lemon

• Salty

  • Ex: Ramen

• Bitter

  • Ex: Coffee

• Umami

  • Ex: Meat

  • Include foods with a savory taste

  • Most recently discovered

• Tongue identifies the different tastes

  • Papillae (raised bumps) on the tongue contain the taste buds

  • Taste buds - the taste receptors that transduce the tastes that we sense

    • Most are on the tongue

• Sensory interaction - when multiple senses work together to influence sensation

  • Ex: flavor is the combination of taste and smell

Smell

Smell is the simplest to understand.

• Olfaction - processing of odors by the brain

• Odors enter the nasal cavity, which has 5 million sensory receptors

• Receptors merge together to form the olfactory nerve, which takes sensory information to the brain

• Smell is not relayed through the thalamus before processing

• Olfactory bulb - part in the brain that processes smell

  • Located close to the limbic system, which processes memory

    • Why smell and memory seem to be closely related

Form

• When we process visual information, our brains tend to organize the information in our visual field

Four Main Gestalt Grouping Principles:

Proximity

When we group things based on how close they are to each other

• Ex: fans for one team are all together, as if one

Similarity

When we group things based on how alike the objects are

• Ex: the home team’s jerseys are red, the visiting team’s jerseys are green

Continuity

When we see objects as continuous and predictable, rather than broken up

• Ex: lines that mark the field

Connectedness

When we see things as connected

• Ex: seeing the offensive players as a whole line

Depth Perception

The ability to identify how far away from us an object is.

• It is innate, which means we are born with the ability to do it

Binocular Cues

The use of both eyes.

• Help us to keep visual perspective in space, determining distance from objects with our eyes through depth perception

• Retinal disparity - as an object gets closer to us, the difference between the images on each retina becomes greater

• Convergence - as an object gets closer, the angle at which the two eyes come together to look at the object becomes greater

  • The eyes appear to be crossed when the object is very close

Monocular Cues

The use of one eye to assess distance.

• Interposition - if object (A) obstructs your view of a different object (B), then (A) must be closer

• Linear perspective - parallel lines appear to converge in the distance

  • Ex: railroad tracks

• Relative Size - an object looks smaller because it’s farther away

  • Objects that are closer should look larger

• Relative clarity - as objects get further away, they appear hazier

  • Objects that are closer appear clearer

• Relative height - we perceive objects high in our visual field as farther away

  • Lower objects are seen as closer

• Light and shadow - cue in which dimmer objects are seen as farther away than light objects

Motion Perception (Relative Motion)

The idea that when you are moving, objects that are farthest away from you move forward through your visual field more slowly than the objects that are closest to you, which move backwards.

• Ex: the tree in the distance seems to move more slowly than the shrubs close to you that are moving backwards

• If you fixate on a point in the distance, objects beyond it appear to move forward, while objects in front of it appear to move backwards

• The brain focuses for distance

  • Perceives motion and organized cues

• When I am moving, things in the distance appear to be moving slowly

Perceptual Constancy

We see objects as unchanging even though they appear differently within our visual field

• Easier because the brain makes adjustments

• Shape Constancy - if the shape cast on the retina changes, we still know the shape of the objects itself has not changed

  • Ex: a closed door casts a rectangle-shape on the retina, an open door casts a trapezoid-shape on the retina, but we understand that the door doesn’t change shapes

  • One of the most well-known types of perceptual constancy

• Size constancy and light constancy are similar types of perceptual constancy

  • Our minds fill in the blanks

  • Ex: if we are in a large room, someone standing across the room has not changed in size because visually they appear smaller. Our minds adjust and perceive that they are simply standing far away from us

  • Ex: although we may be in a dimly lit banquet room we still recognize the people we are visiting with at that party

• Can be challenged with certain visual illusions

  • Ex: the non-right angle room

  • The Muller-Lyer Illusion can cause us to have trouble with perceptual constancy

  • The Ponzo Illusion can cause difficulty in size constancy

    • Notice that the yellow line in distance looks longer than the one closer

    • However, that is counter intuitive to what we know to be true about objects

    • It is an optical illusion because the parallel lines trailing away create this deception

Extrasensory Perception (ESP)

Awareness that occurs beyond the use of the 5 senses and the ability of the mind to “keep reality straight”

• Studied as part of parapsychology (study of paranormal behavioral phenomena)

• VERY controversial

Three Basics Claims

• Telepathy - mind-to-mind communication

• Clairvoyance - ability to perceive things happening in other locations

  • Used by desperate mothers to try to find their children

• Precognition - ability to predict future events