psychology sensing and perception

module 10- sensing the world around us

transduction- transforming sensory stimuli

perception- sorting out, interpretation, analysis, integration of stimuli by sense organs and brain

Psychophysics & Thresholds

psychophysics- study of the relationship between

-actual physical aspects of a stimulus

-our psychological experience of that stimulus

absolute thresholds- weakest stimulus you can detect half of the time

external/internal factors influence our ability to detect weak signals in the environment

intensity of stimulus

interfering stimuli (noise)

psychological state

difference thresholds (just noticeable difference)- smallest level change in stimulation required to sense that a change has occurred

minimum difference between two stimuli that can be noticed 50% of the time

Weber’s Law: a noticeable difference is a constant proportion to the intensity of an initial stimulus

just noticeable difference-

weight detection- 2%

light- 8%

sound/volume- 4%

salt- 8%

electric shock- 1%

Sensory Adaptation

adaptation- is a decline in sensory capacity after prolonged exposure to unchanged stimuli

-sensory nerves receptors can not fire off messages to the brain indefinitlely

  • they’re most responsive to changes in stimulation

Module 11- Vision: Shredding Light on the Eye

vision starts with light (electromagnetic radiation) that stimulates the eye

wavelength: the distance between peaks.

different wavelengths are associated with our perception of different colors

features of color-

  • hue (color)- determined by wavelength of light

  • amplitude (wave height)- determines color’s brightness

  • saturation- purity of the color. uniformity of wavelength

structure of the eye

  • cornea

  • iris

  • pupil

  • lens

  • retina

-photoreceptors: a carpet of neurons covering the back wall of the eye. walls and cones

  • fovea

Transduction-

light passes all the way to the back of the eye

…to rods and cones, which…

…send signals to bipolar cells…

…which pass it on to ganglion cells

..and from the eye to the brain

  • optic nerve: bundle of ganglion axons carries visual info to the brain

-the optic nerve, optic chiasm and pathways to the occipital lobe where visual sensations are processed into perceptions

Processing the Visual Message

  • processing takes place in the visual cortex of the brain

  • feature detectors (shape, pattern, contrast)

  • specialization/integration

color vision and color blindness

trichromatic theory

3 types of cones

yellow-red

green

blue-violet

opponent process theory- receptor cells for color are linked in pairs, working in opposition to each other

red-green

blue-yellow

black-white

  • neurons that respond to these colors below get exhausted and stop firing

  • remove the image, and the opponent neurons fire in response

Module 12- Hearing

audition: the stimulus

  • ears detect waves: sound waves, movement of air molecules brought about by a source of vibration

features of sound

  • frequency (wavelength) number of soundwaves per second (hz) — pitch

  • amplitude: loudness of a sound (decicebels/ dBs)

timbre- quality of the sound- combinations of a dominant frequency, overtones, and undertones

-humans can detect frequencies from 20 Hz to 20 kHz

Auditory System

chochlea: snail-shaped structure filled with liquid

basilar membrane- vibraiting structure through center of chochlea

hair cells - 16,000 receptors for sound waves send to brain

pitch perception

frequency/temporal theory- lower pitches are determined by vibrating frequency of the sound wave, basilar membrane, and neural impulses

place theory- different portions of the basilar membrane are sensitive to different frequencies

sound localization

monaural (one ear): each ear interacts w incoming sound waves differently, depending on the sounds source relative to our bodies

binoral (2 ears) cues- interaural level difference, interaural timing difference