AP Psych Unit 3 - Sensation & Perception

Psychophysics

Psychophysics

the study of how environmental energy can cause a change in emotion and behavior

Reception (step 1 of sensation)

absorption of environmental stimuli (energy) with sensory receptors (eyes, ears, etc.)

Transduction (step 2 of sensation)

physically converting environmental stimuli/energy into neural inpulses

Transmission (step 3 of sensation)

the process of relaying neural impulses to the brain via sensory neurons

Selection (step 1 of perception)

(in hindbrain) the process of filtering the neural impulses via the Reticular Formation

Coding (step 2 of perception)

(in midbrain) organizing stimuli & relaying filtered stimuli to cerebral cortex

Interpretation (step 3 of perception)

(in forebrain) comprehension, analysis, and evaluation of stimuli

Bottom-Up Processing

• Thick slicing

• sensing something before you are able to perceive it

• only method children use to perceive world

Top-Down Processing

• Thin slicing

• cognitive assumptions (expectations based upon experiences & perceptual memory)

• perceiving something first, then being able to sense it

Our conscious mind can process…

40-50 bits per second

Our unconscious mind can process…

11 million bits per second

If there was no natural stimuli filter…

• sensory overload

• inability to focus

• delayed physical reactions

• cognitive delay

• psychosis

Sensory reduction

minimizing the amount of energy absorption at the sensory level

Sensory adaptation

cognitive filtering and adaptation when incoming sensory messages within an environment remain constant & mundane; desensitization within afferent neurons

• picking and choosing selection at hind brain level

Habituation

cognitive filtering when exposed to repeated stimuli over extended periods of time; learning to desensitize due to constant exposure

• learned from experience

Absolute threshold

the lowest limit of stimulus energy that can be physically detected with +50% accuracy

Difference threshold

the measurement of a stimulus’ lowest amount of detectable change of intensity

Weber’s law

states that the just noticeable difference between two stimuli is a constant proportion of the intensity of the original stimulus

• Ex. you would need to add 10 pounds to feel a difference between a 100 pound weight rather than adding 1 pound to feel a difference from a 10 pound weight

Signal detection

consciously adjusting thresholds to become sensitive to specific signals; consciously selecting what signals to pay attention to will accelerate response time

Analgesia

the general inability to experience physical pain

Biological & cognitive purposes of pain…

• acts as a warning that something has gone wrong in the body

• learning mechanism, to promote avoidance behavior to ensure species survival

Nociceptor cells

specialized pain receptor cells; specialized afferent neurons

Substance P

the neurotransmitter responsible for pain sensation

Endorphins

the body’s natural painkillers

Gate control theory of pain

a mechanism, in the spinal cord, in which pain signals can be sent up to the brain to be processed to accentuate the possible perceived pain, or attenuate it at the spinal cord itself

Anticipatory pain

fear and anxiety preceding physical injury; top-down processing

Phantom pain (illusory pain)

false perceptions of pain typically related to limbs / body parts that have been amputated

Sympathy pain

perceiving pain that has been experienced by other people

Wavelength (vision)

horizontal distanced between a wave (light)

• 1 cycle = measurement from crest to crest

Spectrum of visible light

380nm-750nm / 430 Thz - 790 Thz

Frequency (vision)

the number of wavelength cycles that pass through a fixed point per second (vision)

Hue

colors or shades

Low frequency wavelengths (vision)

wavelengths that produce red color (~430Thz)

Infrared waves

light wave frequencies < 430Thz (~1mm-750nm); too low of frequency for human detection

High frequency wavelengths (vision)

wavelengths that produce the color violet (max ~790Thz)

Ultraviolet waves

light wave frequencies > 790Thz (~380-350nm); too high frequency for human detection

Amplitude (vision)

the vertical height of the wave that measures the energy intensity within the wave; provides brightness/darkness or dullness of a color

• low = darker; high = brighter

Saturation

the intensity of the hue

Eye lid

the external protective shield of the eye that blocks debris and light, and cleans/moisturizes the eye

Cornea

• internal shield of the eye

• very sensitive

• reflects light waves

• highest concentration of nerve endings

Pupil

an adjustable tunnel through which light enters the eye

Iris

the colored, donut shaped muscle that regulates the pupil’s diameter; sensitive to amplitude of light wave; melanin protects the retina

Lens

the flexible, transparent disk that focuses light waves onto retina; contour of shape is adjusted by ciliary muscles

Vitreous humor

a clear, gelatinous fluid that fills the ocular chamber to prepare the eye’s spherical shape

Aqueous humor

a clear, gelatinous fluid between the cornea and iris

Retina

projection screen of the lens; transduces light waves into neural impulses

Rods

~120 million per eye; concentrated in the outer rims of the retina

• peripheral vision

• twilight vision

• shades of grey

• sensitive to low amplitude

Cones

~6 million per eye; concentrated in inner core of retina

• color detection

• acuity (fine detail)

• sensitive to high amplitude

• 3rd layer of retina

Macula

• center of retina

• contains the highest concentration of cone photoreceptors

Fovea

the centermost place of the macula (ideal focal point)

Optic nerve

the nerve connecting the retina to the reticular formation; transmits neural impulses to the brain

Blind spot

the place on the retina where the optic nerve is attached and can’t see light

Sclera

the outer membrane of the eye where ocular muscles & blood vessels are attached

Visual accommodation

the ability of the lens to change the contour of it’s shape to allow focus far and near

• ciliary muscles relax, allowing the lens to stretch/flatten for far distance focus

• contraction causes lens to thicken/round for short range focus

How eyes see with limited light…

1. Iris muscles contract causing pupil openings to dilate

2. Photoreceptor sensitivity transfers from the cones to rods

Presbyopia

• transitional blindness

• inability for the lens to accommodate rapidly as it ages and loses flexibility

Myopia (nearsightedness)

• visual impairment at a distance (far things are blurred)

• image is focused at a point in front of the retina

Hyperopia (farsightedness)

• inability to focus images at a close range (troubling seeing things up close)

• image is focused beyond/behind the retina

Astigmatism

• misshaped eye (cornea)

• creates multiple focal points causing visual impairment

Feature detection

the process by which the brain breaks down complex stimuli into specific visual features, such as color, shape, motion, and edges

Selective Attention (Cocktail party phenomenon)

perceptual ability to consciously identify/isolate a single stimuli among a complex mixture of environmental information

Inattentional blindness

failure to detect features within the environment when trying to maintain concentrated focus on a selected stimuli

Change blindness

perceptual phenomenon that occurs when a change in visual stimulus is introduced and the observer is unable to notice it

Illusions

sensory misperceptions that result when cognitive assumptions are proven wrong

Form perception

type of top-down processing strategy that quickly provides the perception of an image based upon it’s relationship between the figure & ground

Figure-ground illusion

misperceptions resulting when distinctions between an image’s figure and ground become blurred

Reversible figure illusions

1 picture that contains 2 images depending on which you perceive as the figure and ground

Closure illusions

perceptual tendency to complete or finish an image when the figure & ground are indistinguishable

Impossible figure illusions

images of objects impossible to construct or design because of laws of physics

Perceptual adaptation

top down ability to adjust to images when presented in a distorted, obstructed, or incomplete view

Perceptual set illusions

perceptual adaptation illusions resulting when our cognitive assumptions are proven wrong when top-down processing an image in a distorted view compared to when processed bottom-up

Thatcher effect

perceptual set illusion involving distorted view of a person’s face

Frame of reference perception

values of an image are perceived based upon how they relate to a frame of reference

Perceptual constancy illusions

despite having equal/constant values, the perceived traits appear to change relative to different frames of reference

• size, shape, and color/brightness constancy illusions

Muller-Lyer Illusion

an example of a size constancy illusion

Parallel processing

the ability of the brain (angular gyrus) to cognitively multitask & process dual functions required by multiple brain structures simultaneously

Perceptual interference illusions

disruptions, delays, & processing failure resulting from conflicts when processing multiple cognitive tasks simultaneously

The Stroop Effect

interference resulting when a singular task requires the use of both cerebral hemispheres simultaneously

The Phi Phenomenon

perceptual illusion of motion caused when stationary images or pulses of light are presented in alternating, rapid succession & are unable to be perceived individually

After image illusions

the residual phantom appearance of an image that temporarily persists after prolonged exposure or because of bad color contrast

Maximum amount of colors and shades of hue that the human color-vision system can detect

~7 million colors/hues

Color blindness

genetic defect affecting the sensitivity of the cones

• Monochromatic (can only see grey)

• Dichromatic (unable to distinguish two colors)

V1 Lateral Geniculate Nucleus (V1 LGN)

• feature detector in occipital lobe

• responsible for the perception of color

Ganglion cells

(1st layer of retina) sensory neurons sensitive to specific frequencies for color detection

Bipolar cells

(2nd layer of retina) sensory neurons that connect photoreceptors to ganglion cells

Opponent Process Theory of Color

Bipolar cells are responsible for detecting colors in opposite pairs; when sensing frequencies of 1 color for prolonged periods of time, the other colors overcompensate

Trichromatic theory

says that cone receptors come in red, green, & blue; each is sensitive to specific light frequency

Depth perception

the ability to gauge approximate size, distance, and relative motion of objects within a 3D space

Linear perspective

• monocular cue

• visual appearance of parallel lines converging as they reach a point in distance

Interposition

• monocular cue

• depth cue caused when multiple objects overlap, creating an appearance of relative distance or order of position

Motion parallax

• monocular cue

• depth perception cue while in motion

• perception of motion is based upon planes of depth

• objects near appear to travel faster than objects far away

Retinal disparity

• binocular cue

• measurement between pupils

• provides the brain with horizontal span of distance needed to triangulate depth

Visual convergence

• binocular cue

• ocular muscles angle inward to focus on near objects, causing the line of sight in both eyes to converge

• provides information the brain needs to triangulate vertical distances

Ames room illusion

example of an illusion that limits stereoscopic vision because it eliminates binocular cues

Wavelength & Frequencies (audition)

• measured as vibrations per second

• as wavelength decreases, frequency increases

Long wavelengths (audition)

• low frequency, low pitch sound

• min threshold ~20 Hz

Short wavelengths (audition)

• high frequency, high pitch sound

• max threshold ~20,000 Hz

Amplitude (audition)

• vertical height of a wave

• provides volume of a sound

• measurement of energy intensity within the wave

Range (tone)

the complexity of a sound when mixed with multiple waves of various frequencies and amplitudes

Timbre

quality/clarity of a sound