Textbook Notes (290,000)
US (110,000)
UC-Irvine (3,000)
PSY BEH (300)
Chapter 5

PSY BEH 11A Chapter Notes - Chapter 5: Outer Ear, Auditory Cortex, Neural Adaptation


Department
Psychology and Social Behavior
Course Code
PSY BEH 11A
Professor
Donald Hoffman
Chapter
5

This preview shows pages 1-3. to view the full 12 pages of the document.
11/20/2017: SENSATION AND PERCEPTION
5.1 HOW DOES PERCEPTION EMERGE FROM SENSATION?
-Sensation: detection of physical stimuli and transmission of that info to the brain
- No interpretation of what we are experiencing
-Perception: brain’s further processing, organization, interpretation of sensory info
- Conscious experience of the world
-Bottom-up processing: based on physical features of the stimulus
- Each sensory aspect of a stimulus is processed, the aspects build up into
perception of that stimulus
-Top-down processing: how knowledge, expectations, past experiences shape the
interpretation of sensory info
- Context affects perception: what we see influences what we perceive
SENSORY INFORMATION IS TRANSLATED INTO MEANINGFUL SIGNALS
-Sensory coding: different features of physical environment are coded by activity in
different neurons
-Transduction: process by which sensory stimuli are converted to signa
-ls the brain can interpret
-Process involves specialized cells in sense organs: sensory receptors
- Receive physical/ chemical stimulation and pass resulting impulses to
brain in form of neural impulses
- Thalamus send info to cerebral cortex interpreted
- Function properly: brain needs qualitative & quantitative info
- Qualitative: most basic qualities of stimulus
- Ex: difference between salty and sweet
- Quantitative: consists of degree/ magnitude of those qualities
- Ex: loudness of honk
DETECTION REQUIRES A CERTAIN AMOUNT OF STIMULUS
-Psychophysics: subfield developed 19th century by Ernst Weber and Gustav Fechner
- Examines psych experiences of physical stimuli
- Study limits of humans’ sensory systems
-Absolute threshold: minimum intensity of stimulation that must occur before you
experience sensation
- Stimulus intensity you would detect more often than by chance
- Ex: hearing faintest sound a person can detect 50% of the time
-Difference threshold (just noticeable difference): smallest difference between 2 stimuli
that you can notice
- Minimum amount of change required for a person to detect difference
- Ex: you’re reading while tv show is on commercial louder than tv can cause
to look up
-Increases as stimulus becomes more intense: Weber’s law
- Just noticeable difference between 2 stimuli is based on proportion of
original rather than fixed amount of difference
- More intense the stimulus, the bigger the change needed

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

-Signal detection theory (SDT): detecting a stimulus is not objective process, but a
subjective one with 2 components
- 1. Sensitivity to stimulus in presence of distractions from other stimuli
- 2. Criteria used to make judgment from ambiguous info
- Ex: in dark room asked if heard a sound says no but might second guess
and convince yourself you heard one
- Hit, miss, false alarm, correct rejection
-Response bias: participant’s tendency to report detecting signal in ambiguous
trial
-Sensory adaptation: decrease in sensitivity to a constant level of stimulation
- Ex: enter friend’s home smells different as time goes on, don’t smell
anything
- When continuous stimulus stops, sensory systems usually respond strongly as
well
THE BRAIN CONSTRUCTS STABLE REPRESENTATIONS
- Most of computations the brain performs never reach your consciousness, only
important new outcomes
5.2 HOW ARE WE ABLE TO SEE?
- Vision: most important source of knowledge
SENSORY RECEPTORS IN THE EYE TRANSMIT VISUAL INFORMATION TO THE BRAIN
- What we see: constructive processes that occur throughout much of brain to produce
visual experiences
-Light passes through cornea: thick, transparent outer layer focuses incoming light
that enters lens: bending light inward & focused to form image on retina: thin inner
surface of back of eyeball
- Retina: only part of brain we can see
- Contains sensory receptors that transduce light into neural signals
- Light focuses more at cornea > lens
-Pupil: dark circle center of eye, small opening in front of lens
- Contracting or dilating: determines how much light enters eye
- Dilates in dim light/ something we like, contracts in bright
-Iris: circular muscle
- Determines eye’s color & controls pupil’s size
-Accommodation: flatten to focus on far away, thicken to focus on closer objects
- Retina has 2 types of receptor cells
-Rods
- Respond at extremely low levels of light
- Night vision
- No color vision
- Poor at fine detail
- Cones
- Less sensitive to low levels of light

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

- Visions under brighter conditions
- Seeing both color & detail
- 120 million rods/ 6 million cones
-Center: cones densely packed in fovea
- Scarce near outside edge
- Rods: near edge
- Visual process begins with generation of electrical signals by sensory receptors in retina
-Contain photopigments: protein molecules that become unstable & split apart
when exposed to light
- Decomposition alters membrane potential of photoreceptors & triggers
action potentials
-Ganglion cells: first neurons in visual pathway with axons, after transduced by
rods and cones
- Signals from eye thalamus
-Gathered in optic nerve, exits the eye at back of retina
- Has no rods or cones blind spot
-Optic chiasm: half of axons in optic nerves cross
- Only ones that cross: start from portion of retina nearest nose
- Causes info form left side of visual space to be projected to right
hemisphere
-Info reaches thalamus primary visual cortex: cortical area in occipital lobes at
back of head
- Important theory: visual areas beyond primary visual cortex form 2 parallel processing
streams/ pathways
-Ventral stream: lower. Specialized for perception & recognition of objects
- Colors and shapes
- “What” stream
-Dorsal stream: upper. Specialized for spatial perception
- Where object is & related to other objects
- “Where” stream
- Damage to visual cortex: evidence between the 2 streams
- CASE STUDY: D.F.
- Age 34. Suffered carbon monoxide poisoning damaged visual
system
- Cannot recognize face bc damage to ventral stream, but can
recognize voices
- Can use visual info about the image. Use dorsal stream
-Object agnosia: inability to recognize objects
- Ex: can draw apple from memory, but asked what the
picture is, cannot identify
THE COLOR OF LIGHT IS DETERMINED BY ITS WAVELENGTH
- Color wavelength of light it reflects
- Not property of object
You're Reading a Preview

Unlock to view full version