Unit 1B: Sensation & Perception - AP Psychology

What is sensation vs. perception and psychophysics?

Sensation:

• The experience of sensory stimulation

• Ex: “I see something”

Perception:

• Creating meaningful patterns from raw sensory information

• Ex: “I see a dog”

Psychophysics: the study of the relationship between physical stimuli and our experiences of them → how does our mind interpret different things?

What are the two types of processing data that you see?

Bottom-up processing (data-driven)

• Beginning w/ stimulation of our senses, we interpret sensory info w/ our brains

• Collecting data and clues as to what you’re looking at

• Ex: I see a furry, 4-legged creature w/ a tail & identify this as a dog

Top-down processing (schema-driven)

• Using our schemas, expectancies & past experiences, we interpret sensory info to construct deeper meaning

• Comparing incoming data to what you’ve seen prior & waiting for a match

• Ex: The dog is growling and foaming at the mouth and I realize it may have rabies, so I won’t pet it

**these two processes happen at the same time

How do we interpret “sensation”?

Receptor cells → receives incoming sensory info & are located in different locations and are specific to their location

• Specialized cells that respond to a particular type of energy

• These exist in your sense organs

• These cells are located in your eyes, ears, etc

Ex: receptor cells in the eyes can only SEE and not SMELL b/c they’re not in the nose

What is the law of specific nerve energies?

Muller is the one who made the law

• One-to-one relationship between stimulation of a specific nerve and the resulting sensory experience

Ex: applying pressure w/ your finger to your eye results in a visual experience

What are sensory thresholds?

Absolute threshold

• The minimum amount of energy that can be detected 50% of the time

• When the limit is reached, something happens

Ex: at what point can you hear the presence of a sound?

What is a sensory adaptation?

An adjustment of the senses to the level of stimulation they’re receiving 

• Rods & cones become sensitive to the few light waves there are in a place → ex: being in a dark place, rods and cones become desensitized to the decreased amount of light waves

• Sensory adaptations applies to all receptors 

What is the difference threshold?

The smallest change in stimulation that can be detected 50% of the time (aka just noticeable difference) → what’s the smallest amount of change in stimulation where you can notice the difference?

• Ex: at what point can you tell that the TV volume has been raised?

What is Weber’s Law?

States that the difference threshold is detected by a constant minimum percentage of the stimulus, not a constant amount

• Weight of the thing that’s relative to what’s there

• Ex: to detect a different in weight, the change must be 2% of the original stimulus’ weight

What is subliminal perception?

The processing of information by the brain without conscious awareness.

• Occurs when stimuli are presented at a level below the threshold of conscious perception

• Can still influence thoughts, feelings, and behavior

Ex: a main character driving a Ford during a movie → subliminally watching an ad

What is the signal detection theory?

It challenges the notion of the absolute threshold

• The SDT is a mathematical model that predicts how and when we will detect the presence of a faint stimulus or signal

• States that there’s NO single absolute threshold

• Detection of a stimulus depends on a person’s experience, expectations, motivations, and fatigue

• Some don’t believe that absolute thresholds are real/valid → part of this theory

• Says we’re all unique individuals that and makes us different on how we perceive sensation

What is transduction?

Our eyes have the ability to convert one form of energy (in this case, LIGHT) into messages that our brain can interpret as a visual experience

• We can only see a small part of the electromagnetic spectrum

• To transduce: one of your sense organs is processing incoming sensory info

• Some kind of wave or molecule is coming into contact w/ one of your sense organs

What is the cornea?

Transparent protective coating over the front of the eye

• Light hits this first 

What is the pupil?

Small opening in the iris through which light enters the eye

• Light hits this second after the cornea

What is the iris?

Colored part of the eye; controls size of pupil

• A muscle that surrounds the pupil that can dilate and constrict your pupil

What are the lens?

Focuses light into the retina, changes shape through accommodation to help focus image on retina → another muscle that can also expand and contract

• When lens contract, it helps you to see close up things → near-sightedness is mostly caused by your lens being permanently contracted. Vice versa for far sightedness

What is the retina?

Lining of the eye containing receptor cells that are sensitive to light

• Made up of rods/cones

• Don’t allow us to see color, but they’re not aligned w/ the fovea

• Rods amke up the top and bottom of the eye

What is the fovea?

Center of the visual field

• Indentation in the retina that lines up with your pupil → all cones are in the fovea

What’s the optic nerve?

Links the eye to the brain

• Creates a blind spot b/c there are no receptor cells there

• Made up of bipolar & ganglion cells 

What are the receptor cells in the eye?

Cells in the retina that are sensitive to light

• Visual receptors are called rods and cones

• Rods can’t detect color at all → associated w/ peripheral vision

• Cones can detect color

What are the different receptor cells in the eye?

Bipolar cells & ganglion cells (blind spot)

What are bipolar cells?

Receives input from receptor cells

What are ganglion cells?

Receive in put from bipolar cells

• Axons of these cells form optic nerves

What is a blind spot?

Area where axons of ganglion cells leave the eye

• NO RECEPTORS in here

What is the order of info that goes to your brain?

Receptor cells → bipolar cells → ganglion cells → brain

How is the eye and the brain connected?

Through the optic nerve

• The optic chiasm is the point where part of each optic nerve crosses to the other side of the brain

• The thalamus relays sensory info to visual cortex in occipital lobe

What is feature detection?

Feature detectors are neurons in the brain that respond to specific aspects of a stimulus

• Edges, lines, movements, and angles

• Simple, complex, hypercomplex

• Visual cortex → supercell clusters

• Supercell clusters that integrate info from the feature detectors that the fusiform recognizes specific people or things

What are supercell clusters?

Neurons that work in teams to determine familiar patterns, such as faces 

• Processed in the right-side of temporal lobe

Face blindness or procophasia: people have features & supercell clusters, but the part that puts it together has a problem

What is parallel processing?

Our brains process multiple features of visual experience at once and integrate these features to create what you’re looking at

What are super recognizers?

People have an in depth of fusiform formation and they will never forget that face

What are the theories of color vision?

Additive color mixing

• Mixing of lights of different hues

• Lights, TV, computer monitors (RGB)

• Lights add wavelengths

Subtractive color mixing 

• Mixing pigments (ex: paints)

• Pigments absorb or subtract wavelength

Trichromatic Theory (Young-Helmholtz)

What is the trichromatic theory?

Says there are three different types of cones: red, green, blue

• Experience of color is the result of mixing of the signals from these receptors

• Advantage: can account for some types of colorblindness

• Dichromats: two colors only

• Monochromats: one color only

Opponent processing theory says that there are different cones responsible for perceiving different colors

What are the disadvantages of the trichromatic theory?

• Red-green colorblind people can see yellow, which Helmholtz argues is a result of red and green cones firing - if Helmholtz is correct, how could this be?

• No explanation for color afterimages

• Why can’t we see “reddish-green” or “yellow-blue”?

What is the opponent-process theory?

States that there are three pairs of color receptors

1. yellow-blue

2. red-green

3. black-white

• Members of each pair work in opposition

• Advantage: can explain color afterimages

What are the different types of adaptation in vision?

Dark adaptation

• Increased sensitivity of rods and cones in darkness

Light adaptation

• Decreased sensitivity of rods and cones in bright light

Afterimage effect

• Sensory experience lasts even after a visual stimulus has been removed b/c of the overstimulation of receptors

What is sound and the different parts that come w/ it?

We hear by transduction of sound waves into nerve impulses

• A sound wave is a change of pressure in the air, and how frequently a sound wave repeats in a second dictates the pitch

• Higher pitch = more times a sound wave repeats in a second

• Frequency, amplitude, overtones, timbre

What is frequency?

Frequency determines pitch, which is measured in Hz

What is amplitude?

It determines loudness, which is measured in decibels (dB)

• Amplitude dictates how loud a sound is

• Higher amplitude = louder sound

What are overtones?

Multiples of the basic tone

• Multiple of the same sound wave hitting your ear at the same time

What is a timbre?

The quality of texture of sound

• The difference between a piano and a violin playing at the same amplitude, frequency, and musical note, BUT it still sounds different

What are the different parts of the ear?

Outer ear, middle ear, and inner ear

What are the parts of the outer ear?

• Pinna

• Tympanic membrane (eardrum)

What are the parts of the middle ear?

Contains three auditory ossicles (bones)

1. Malleus (hammer)

2. Incus (anvil)

3. Stapes (Stirrup)

These bones relay and amplify the incoming sound waves

What are the parts of the inner ear?

• Oval window set in motion by ossicles

• Fluid-filled cochlea

• Basilar membrane set in motion by the rippling fluid

• Organ of corti sits atop the basilar membrane and contains w/ cilia (hair cells) which bend as basilar membrane vibrates