sensation & perception

sensation

stimulation of a sense organ

perception

organization, identification and interepretation of a sensation in order to form a mental rep

synaesthesia

perceptual experience of one sense that is evoked by another sense

sense: vision , sensory output

light reflected from surfaces, provides vision with information

sense: audition

vibrations cause changes in air pressure that move through space to the listeners ears

sense: touch

pressure from surface against the skin, signals shape, texture, temprature

sense: taste & smell

molecules dispersed in the air or dissolved saliva reveal the identity of substances that we may or may not want to eat

Psychophysics

Methods used to measure the strength of a stimulus and observers sensitivity to said stimulus

psychophysicists

measure minimum amount of stimulus that is needed to be detected

Thresholds ( just noticeable difference)

minimal change in a stimulus that can just barely be detected

webers law

just noticible diff of a stimulus is a constant proportion despite variations in intensity This principle states that the ratio of the increment threshold to the background intensity is a constant.

visual acuity

ability to see fine details

visible light

portion of electromagnetic spectrum seen

length v amplitude v purity

length: hue or what we perceive as colour
Amplitude: brightness
purity: saturation or richness of colour

Anatomy of the eye (general)

cornea > pupil> iris> lens>retina> fovea> retinal surface> optic nerve> blind spot

myopia & hyperopia

myopia: nearsightness
hyperopia: farsightness

CONES, FOVEA, RODS

cones: detect ccolour, operate under normal daylight , detects fine details
fovea: area of retina where vision is clearest, no rods only cones

rods: become active under low light conditions / night vision

photoreceptors: rods & cones

light reaches back of retina, triggers in receptor cells (rods and cones)

the rods and cones turn and send messages to ganglion and bipolar cells on the optic nerve

rods help us see the black and white actions in our peripheral view and in the dark. rods are more common than cones, which helps us see sharp colourful details

retina & blindspot

retina: layers of cells, bipolar cells and retinal ganglion cells ( in addition to the rod and cone layers )

blind spot: location in visual field that produces no sensation of the retina, cuz it contains neither rods or cones, therefore has no mechanism to sense light

perceiving colour: wavelengths, long , medium, short

red: long wavelength
green: medium wavelength
blue: short wavelength

the visual brain:

streams of action potentials containing info encoded by the retina to travel to brain for further processing.

ateral geniculate nucleus (LGN), v1:

part of the occipital lobe that contains the primary visual cortext

The visual brain: ventral stream & dorsal stream

ventral: he “what” to the temporal lobe

dorsal: the “ where” to parietal lobe

visual form agnosia

inability to recognize objects by sight

binding problem

how features are linked together so that we see unified objects rather than free floating or mis combined features

errors in binding problem: illusory conjunction

perceptual mistake where features from multiple objects are incorrectly combined

errors in binding problem: feature integration theory

idea that focused attention is not required to detect the individual features that comprise a stimulus, but is required to bind those features together

binding process

utilizes structures in ventral and especially dorsal stream ( parietal lobe )

molecular depth cues

aspects of a scene that yield info about depth when viewed with one eye

binocular disparity

difference in retinal images of the two eyes that provide info about depth

hearing & sound waves

hearing: detection of sound waves or changes in air pressure

sound waves: involve qualities of frequency, amplitude, and timbre

properties of sound waves: frequency, amplitude, complexity

frequency: corresponds to our perception of pitch

amplitude: perception of loudness

complexity: perception of timbre ( listeners experience of sound quality or resonance)

The human ear is divided into three distinct parts: basic

outer ear: collects sound waves

middle ear: transmits vibrations

inner ear: transduction into neural impulses

the human ear: transduction in the ear involves several structures

cochlea

basilar membrane

hair cells

The human ear: Area A1

portion of temporal lobe that contains the primary auditory cortex

The human ear: Area A1: spatial and non spatial

spatial: ‘where’ auditory features locate source of sound

non spatial: “what” auditory features locate temporal aspects of a sound

the human ear: enoding, place code and temporal code

place code: cochlea encodes diff frequencies at diff locations along basilar membrane

temporal code: cochlea registers low frequencies via firing rate of action potientals

hearing loss has 2 main causes

conductive hearing loss: damage to ear drum or ossicles

sensorineural hearing loss: damage to cochlea , hair cells or auditory nerve