Psychophysics: 

Relationship between physical stimuli and sensations/perceptions they create

Necker Cube:

• Perception can be ambiguous

• Produces two perceptions 

  • Stimulus does not change but what we experience does

Sensory transduction:

• Receptors convert a physical energy/ image into nerve impulses

Words to know:

Exteroception: 5 senses

Introception: perception from inside of body

What we notice:

• Only 1% of the outside world is what we notice, the rest is filtered

Selection:

• Selecting where to direct our attention is the first step in perception

• Selective attention/ features detectors help explain why we pay attention to some stimuli and not others

Feature detectors:

• Brain has specialized neurons → responds to only certain stimuli

• Occipital lobes visual cortez

• Respond to special features of an image

  • Angles, lines, curves, movements 

Cocktail party effect:

• Auditory blindness

Change Blindness:

• Are we paying attention?

Exploring the senses: 

Subliminal: below what we could sense

Absolute threshold: smallest level of stimuli that can be detected at least 50% of the time

Absolute threshold:

vision: smallest level of light a person can detect

• How far a person can stand away from a candle and see the flame

oders: smallest level of a small a person can detect

• How little perfume in a large room

touch: the amount of force required to detect a feeling on your body

• Can vary depends on which part of the body (HOMUNCULUS)

Just Noticeable Difference:

Smallest change a person can detect 50% of the time

Weber's Law:

Ability to notice a change in stimulus in proportion to intensity of stimulus

LARGE JND: high intensity

SMALL JND: low intensity

• CONSTANT PROPORTION, NOT AMOUNT

Bottom up VS Top down processing:

Bottom up: relies on properties of the stimulus (patterns of light and dark areas)

Top down: relies on higher level info (prior knowledge and experience)

Sensory Adaptation Vs Habituation  

Habituation:  gradually over time and involuntarily.  

Sensory Adaptation: being exposed to the stimuli and getting used to it.  

Subliminal threshold:

Subliminal threshold: when energy of threshold is below one's absolute threshold for conscious awareness

Single detection theory: 

NO single absolute threshold (instead: intensity of stimulus, background noise, and motivation.)

Vision: 

Cornea: outer layer of eye

Iris: color

Lens: lies behind the eye and bends light

Retina: thin layer of cells in back of eye (FOCUSES LIGHT ON PARTICULAR POINT)

Cells:

Photoreceptor: detects light and color

Rods: black/ white

Cones: colors, bright light

Bipolar: passes signals

Ganglion: sends visual info from retina to brain

Visual transduction:

Transduction: stimulus becomes electrical signal processed by brain

Light:

Form of energy composed of photons (energy)

• Rods / cones are photon receptors

• Only bends when going through transparent materials

Color/ electromagnetic energy:

We DO NOT see color, we see electromagnetic energy

Physical characteristics:

Wave length: the distance from the peak of one light or sound wave to the next

Hue: dimension of color

Intensity: amount of energy in light/ sound wave (DETERMINED BY AMP)

Color does not exist: 

Color is made up of wavelengths of light that are visible to us

Visible light spectrum:

High = fast (RED)

Low = slow (PURPLE)

Two theories:

• Trichromatic theory: HELMHOLTZ AND YOUNG)

  • RBG

    • Retina ←> fovea

    • Color ←> 3 cones

  • Rods: most sensitive to light/ dark changes + movement found on the periphery of the retina

  • Cones: only in bright light, used for color vision + fine detail

• Opponent processing: (EWALD HERING)

  • Our color perception is controlled by color combos we do not see

    • Inhibitory / excitatory response

  • Occurs in ganglion cells and in the thalamus (LGN)

  • After images are activated and others are not

    • red/ green, blue/ yellow, black/ white

Color blindness: 

• Most commonly through genetics

• Found on the X chromosome

Symptoms:

• Differentiating how bright colors are

• Differentiating the shades of the colors

• Difference between the colors

How:

If a person lacks in a cone, they are color blind

Lateral inhibition: 

Capacity of excited neurons to reduce capacity of neighboring neurons