Sensation and Perception

transduction

signals are transformed into neural impulses

sensation

activation of our senses

perception

process of understanding

what is the dominant sense in humans?

vision

what are the four steps of vision?

1. gathering light

2. within the eye

3. transduction

4. in the brain

what happens when gathering light? (step one)

light is reflected off objects and gathered by the eye

what does the color we see depend on?

energy in light and the wavelength

what color has the longest wavelength? the shortest?

longest- red

shortest- violet

cornea

protective covering over the eye, helps focus light

pupil

muscles (iris) dilate and constrict or don’t constrict to let light in or not

lens

focuses light from pupil, curved and flexible

retina

projects image, contains neurons activated by different light wavelengths

what is the sensation pathway for vision?

light → cornea → pupil → iris → strikes the lens → retina → rods/cones → optic nerve → optic chiasm → thalamus → occipital lobe

when does vision transduction occur? (step three)

occurs when light activates neurons in retina

what is transduction?

translation of incoming stimuli into neural signals (applies to all senses)

cones

high light levels and see color; found in center of retina (fovea)

rods

low light levels and to see black and white

optic nerve

made of axons of ganglion cells; sends impulses to thalamus

optic chiasm

the spot where left and right impulse nerves cross

what happens in the brain during vision? (step 4)

retina impulses → visual cortex → activate feature detectors

trichromatic theory of color vision

human color vision relies on red, green, and blue cone cells in the retina

opponent-process theory of color vision

• sensory receptors in the retina come in pairs: R/G, Y/B, B/W

• when color is perceived, the other color is suppressed

sound waves

vibrations in the air

amplitude

height, determines loudness

frequency

length, determines pitch

what is the sensation pathway for hearing?

sound waves → pinna → auditory canal → tympanic membrane → ossicles (malleus, incus, stapes) → oval window → cochlea → basilar membrane - hair cells → vestibulocochlear nerve → thalamus → temporal lobes

what are the three parts of the eardrum?

malleus, incus, stapes

place theory of pitch

hair cells in cochlea respond to different sound frequencies based on their location

frequency theory of pitch

pitch is determined by the rate at which auditory nerve fibers fire in response to the sound’s frequency

when does conduction deafness occur?

when something is wrong with the system of conducting the sound to cochlea

when does nerve deafness occur?

when hair cells in cochlea are damaged

how does touch work?

brain interprets amount of indentation (or temp. change) as intensity of touch

how do we sense touch?

where nerve endings fire on body (the more concentrated = more sense)

gate-control theory

some pain messages have higher priority than others

what five tastes do we have?

sweet, salty, sour, bitter, umami (savory)

how do we taste things?

chemicals from food are absorbed by taste buds on tongue

what is the sensation pathway for tasting?

Tongue → cranial nerves → brainstem → thalamus → gustatory cortex in the cerebrum

what is the sensation pathway for smelling?

Odor molecules → olfactory epithelium → olfactory neurons → thalamus → olfactory bulb → olfactory cortex

what is smell crucial for?

indentifying food and avoiding danger

what is smell linked to?

memory and emotion

what does our vestibular sense do?

tells us about how our body is oriented in space

what is the sensation pathway for our vestibular sense?

Head movements (fluid moves in inner ear) → Vestibular nerve → vestibular nuclei in brainstem → thalamus → cerebellum

what does our kinesthetic sense do?

gives us feedback about the position and orientation of specific body parts

what is the sensation pathway for our kinesthetic sense?

Sensory receptors in muscles, tendons, and joints → spinal cord → brainstem → thalamus → cerebellum

what is the sensation pathway for touch?

Sensory nerves → spinal cord → thalamus → somatosensory cortex

psychophysics

study of the interaction between sensations we receive and our experience of them

absolute threshold

smallest amount of stimulus we can detect

difference threshold

smallest amount of change needed in a stimulus before we detect a change

what does weber’s law state?

the change needed is proportional to the original intensity of the stimulus

signal detection theory

a framework for understanding how people make decisions in the presence of uncertainty and background noise

what is the sensation pathway for gustation (tasting)?

Tongue → cranial nerves → brainstem → thalamus → gustatory cortex in the cerebrum

top-down processing

our brains interpret sensory information using prior knowledge, expectation, and context

schemata

mental representations of how we expect the world to be

bottom-up processing

perception starts with sensory input and builds up to a complete understanding without using prior knowledge or expectations

what is a hit?

when an observer correctly identifies the presence of a signal that is actually there

what is a miss?

where a person fails to detect a signal when it was actually present

what is a false positive?

when a person incorrectly perceives a signal as being present when there is only noise

what is a correct rejection?

when an observer correctly decides that a signal is absent when there is actually no signal present

what is the figure-ground relationship?

determining what's the figure and what’s the ground/background

what does gestalt say about processing images?

we process images as groups, not as isolated elements

what are the four Gestalt principles?

1. proximity

2. similarity

3. continuity

4. closure

according to gestalt, things belong in a group if they…

1. are close together

2. look similar

3. form a continuous form

4. make up a recognizable image

constancy

our ability to maintain a constant perception of an object despite changes in size, shape, or brightness

perceived motion

the brain’s interpretation of changes in visual input over time to infer an object’s speed and direction

monocular depth cues

visual signals that allow a person to perceive depth and distance using only one eye

binocular depth cues

visual signals that use both eyes for depth, allowing us to see 3D by comparing the slightly different images from each eye

extrasensory perception (ESP)

the controversial claim that perception can occur apart from the five known senses (eg. telepathy, precognition)