Textbook Notes (280,000)
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Chapter

detailed textbook notes, plus extra stuff from lecture


Department
Psychology
Course Code
PSYA01H3
Professor
Steve Joordens

Page:
of 6
●One rock group accused of encouraging suicide by including command β€œdo it”
recorded backward
●Begg, Needham, Bookbinder – examined this by playing backwards or
forwards message and tested whether people could recognize message played
backward and whether they agreed with message played in forward direction
found that hearing backward message helped you recognize same message
played backward again – but meaning was lost
●subliminal perception – perception of stimulus, as indicated by a change in
behaviour, at an intensity sufficient to produce a conscious sensation
person denies detecting stimulus yet stimulus has measurable effect on
behaviour
effects are subtle and special procedures required to demonstrate them
β– Cheesman and Merikle – looked at effect of presenting word just
before students were asked idenity colour of brief flash of light
●if word and colour name were different then it took longer to identiy
colour – incongruent priming
β– indicate that perception is complex process
●involves sense receptors and physiological process
●Merickle – some tapes contain messages that are too weak for human ear to
detect under any conditions and some when subjected to specrtographic
analysis (detects voiceprints) contained none at all
●Pratkanis – tapes for memory or self-esteem – participants didn't know which
was which and mixed them up
Vision
Light
●light consists of radiant energy similar to radio waves – oscillates as it is
transmitted from source
●wavelength – distance between adjacent waves of radiant energy; in vision,
most clearly associated with perceptual dimension of hue
●wavelegnth for visible light ranges from 380-760 nanometres (380 – violet, 760
– red)
●entire range of wavelength is called electromagnetic spectrum and part our
eyes can detect is visible spectrum
The Eye and Its Function
●cornea – transparent tissue covering front of eye; admits light
●sclera – tough white membrane that is outer layer of eye
●iris – pigmented muscle of eye that controls size of pupil – contains two bands
of muscle
brain controls these muscles and regulates size of pupil
●aqueous humour - space behin cornea is filled with (watery fluid)
constantly produced by tissue behin cornea that filters fluid from blood
nourishes cornea and other portions of eye in place of blood vessels – must
circulate
if produced too quickly or if passage that returns it to blood becomes
blocked, pressure within eye can increase and cause damage to vision
(glaucoma)
no blood vessels – transparency of cornea
●lens – transparent organ situated behin iris of eye; helps focus an image on
retina (inner surface of back of eye)
image is upside down and reversed from left to right
brain compensates for this alteration and interprets information
appropriately
contains no blood vessels – functionally dead tissue
shape is flexible – special set of muscles can alter shape so eye can obtain
images of nearby or distant objects
accommodation- change in shape of lens to adjust for distance
●length of eye normally matches bending of light rays produced by cornea and
lens so that image of visual scene is sharply focused on retina
for some people length of eye doesn not match bedning of light rays so
iamge is out of focus – need extra lens in front of eye
near sighted - eyes too long (front to back) so need concave lens to
correct focus
far sighted – eyes too short so need convex lens
as people age, lens becomes less flexible and becomes difficult to focus on
objects close to them – need convex lens
●retina – tissue at back of inside surface of eye that contains photoreceptors
and associated neurons (performs sensory functions of eye)
embedded in retina are over 130 million photoreceptors
photoreceptors – receptive cell for vision in retina (rod or cone);
specialized neurons transduce light into neural activity
β– information from photoreceptors is transmitted to neurons that send
axons toward one point at back of eye (optic disc)
β– optic disc – circular structure located at exit point from retina of axons
of ganglion cells that form optic nerve; all axons leave eye at this point
and join optic nerve which travels to brain
β– no photoreceptors in form of optic disc so that portion of retina is blind
retina has three layers – light passes successively through ganglion cells
(front), bipolar cells (middle) and photoreceptor layer (back)
β– cells located above photoreceptors are transparent
●Johannes Kepler – astronomer suggested that retina, not lens, contained
receptive tissue of eye
●Christopher Scheiner – 1625 proved that lens is only focusing device
●photoreceptors respond to light and pass info to bipolar cells by means of
transmitter substance
bipolar cells – neuron in retina that receives information form
photoreceptors and passes it on to ganglion cells, from which axons
proceed through optic nerves to brain
●bipolar cells transmit information to ganglion
ganglion cells – neuron in retina that receives informaiton from
photoreceptors by means of bipolar cells and form which axons proceed to
optiv nerves to brain
●photoreceptor – responds to light that reaches its immediate vicinity
●ganglion cells – responds to information from many different photoreceptors
●retina also contains neurons that interconnect both adjacent photoreceptors
and adjacent ganglion cells – indicates that some kinds of information
processing are performed in retina
●retina – contains 2 types of photoreceptors: 125 million rods and 6 millions
cones
●rods – sensitive to light but cannot detect changes in hue; function in dim light
●cones – responsible for acute daytime vision and for colour perception;
function when light is bright enough to see things clearly
●fovea – small pit near centre of retina containing densley packed cones;
responsible for most acut and detailed vision; 1 mm in diameter
cones connected to one ganglion each
when we look at point in visual field, we move our eyes so that image of
that point falls directly on cone-packed fovea
●rods – increase as move further from fovea; connected to many ganglion (up to
100 each)
ganglion receiving info from many rods is sensitive to very low levels of light
rods are responsible for sensitivity to dim light but visual information lacks
sharpness
Transduciton of Light by Photoreceptors
●molecule responsible for transduction is derived from vitamin A, in absence of
light it is attached to protein and forms photopigment
photopigment – complex molecule found in photoreceptors; when struck
by light, splits apart and stimulates membrane of photoreceptor in which it
resides
●photoreceptors of human eye contain 4 kinds of pigment (1 for rods, 3 for
cones)
●when photon strikes photopigment it splits apart into 2 molecules causing
series of chemical reactions that stimulate photoreceptor and causes it to send
message to bipolar cell and form synapse
●bipolar cell sends message to ganglion cell – sends message to brain
●intact pigment has characteristic colour (Rhodopsin, in rod, is pink) but are
bleached once split apart
●Franz Boll – discovered this when he removed eye from animal, pointed it
toward light and found image on retina was still there but faded where light
had fallen – led investigators to suspect chemical reaction
●after photopigment is split, energy from photoreceptor's metabolism cause 2
moelcules to recombine and is ready to be bleached again
●photoreceptors – contain thousands of molecules of photopigment each;
number intact depends on rate which they are being split and put back
together
Adaption to Light and Dark
●dark adaption – process by which eye becomes capable of distinguishing
dimly illuminated objects after going from bright to dark area
●when high levels of illumination strike retina, regeneration falls behin bleaching
so rods aren't sensitive to light (only small number of photopigment intact –
probability that photon will strike molecule is low)
●eventually regeneration overcomes bleaching process