Cognitive and biopsychology lecture 3 Flashcards
What is bottom up attention?
passive modes of attention, exogenous attention. Alertness or arousal, reflexive attention (towards a bolt of lightning)
what is top down attention?
active modes of attention, endogenous attention. selective attention choosing whether to listen and look at lecturer
What are the cells of the retina made up of?
photoreceptor cells and can be broken down into two areas:
fovea (more cells - most cones)
parafovea (less cells - most rods)
what is the fovea?
centre of retina
what is the diameter of the fovea?
1mm
what does the fovea have?
high concentration of cone photoreceptors (colour, high spatial acuity0
What percentage of optic nerve fibers come from the fovea?
50%
Where in the eye is the greatest visual accuracy achieved?
in the fovea - further away from retina lower the acuity
what needs to be processed in the fovea?
areas of detail
what is the parafovea?
higher density of rod photoreceptors
what are the characteristics of the parafovea?
- no colour
- low spatial acuity
- better with low light vision and motion
What is a fixation?
when an eye is table
what is the saccade?
when they eye is moving in a ballistic way
How many eye movements are made per second?
3 eye movements
What does a brain do with our eye movements?
brain fills in the gap and uses our frequent eye movements to update and hold visual info.
How is the perception of the world made?
by amalgamating visual snapshots and knowledge about our environment
What is saccadic suppression
don’t perceive our own saccades
Why does saccadic suppression happen?
to suppress motion blur during the saccades
How many visual degrees per second can the eye
travel up to?
900 visual degrees per second (perceive a stable world)
what is overt attention
focus of attention is what fovea is currently looking at
what is attended info?
info in or around the fovea
what is unattended info
everything else
Characteristics of overt attention
slow - around 3-4 saccades per second (1 every 300 ms)
Characteristics of covert attention?
faster - 50ms to shift
what is covert visual attention?
attentional spotlight: focused visual attention resembles a spotlightb
example of covert visual attention
enhance attention w/in a small region of the visual field but not outside the beam of attentional spotlight (Posner 1980)
What is attention directed to?
a given region of the visual field
What can the area of focal attention be?
increased or decreased depending on task demands (Erikson & St. James, 1986)
what is covert attention?
when we attend somewhere or to smth w/out moving our eyes
what does covert attention do?
acts a filter - selects stimuli for further processing
limited in capacity - it appears that resource can be divided up depending on the task demands
Helmholtz on covert attention (1867)
can enhance perception if focus attention on a location in visual field. Comes at the expense of other areas of the visual field.
Themes that characterise attention
capacity limitation
perceptual gating
what is capacity limitation?
our limited ability to carry out various mental operations at the same time needs a way to prioritse info
what is perceptual gating?
conscious perception is always selective, but selection isn’t always conscious
what is selective attention?
selectively attend to certain stimuli in our environment while ignoring others. Present 2 or more stimuli inputs, instruction to respond to just one
What is divided attention?
ability to undertake several tasks at once. Present at least 2 stimulus inputs, instruction to respond to all
What is the problem of attention in vision?
limits how much we can take in, bc things in environment placed in different spatial location
what is the problem of attention in terms auditon?
streams of sound from different locations
What did Welford do (1952)?
presented 2 signals in rapid suc, Psychological refract period paradigm. Ppts make speeded response to both. Reaction time to 2nd stim depends on how close presented to 1st stim. Closer presentation slower reaction time
what did welford see this as evidence of?
a bottleneck (early selection)
why did welford call it a botttleneck?
bc processing of one stimulus must be completed before the processing of the next one can begin
what did he also claim it was good evidence for?
a central limit on human processing capabiltiy
What was Cherry interested>
Cherrry in 1953 was interested in the cocktail party phenomena
What is the cocktail party phenomena?
we can follow one convo while several ppl talking
What is the shadowing task?
dichotic listening procedure - shadow means to repeat aloud the message to attend to
What did Cherry find?
ppts weren’t able to:
detect the meaning of the 2nd stream
detect if 2nd stream was a foreign language or reversed speech
repeat any words in the 2nd stream
What did Broadbent (1958) do ?
dichotic listening procedure, 3 digits presented to one ear at same time as another 3 digits presented in other ear
What did Broadbent find?
ppts would recall no. ear by ear better than in pairs
suggested stimuli accessed in parallel by a sensory buffer
buffer filters stimuli based on physical characteristics
other input remains the buffer
What is Broadbent’s filter theory of attention? (1958, 1971)
attention allows to selectively process info
filter relevant info
sensory register - selective filter - STM. Argues we can’t identify or process smth w/out attention
Evaluating broadbent
based on physical props and therefore inflexible
What did Treisman (1960) say about Broadbent’s filter theory?
ppl switch attention info unattended info meaningful in current situation. At a party and somebody in convo but not directly involved but name is mentioned name may switch attention and monitor that convo.
What modification did Treisman made to Boradbent’s split span procedure?
ppl don’t like switching ears to gather info but do if info makes sense e..g listening to a story coming in from 1 ear and random digits to other but if that suddenly switches you switch attention to other ear. You follow the meaning.
What did Gray and Wedderburn (1960) find?
dichotic task “Who goes there” and “461”, ppts better at reporting “who goes there” and “461” (top down)
Attenuation (Treisman 1964)
sometimes unattended items are processed. Filter occurs depends on task demands.
sensory register - attenuator - STM
sometimes means unattended items leak through filter as processed enough to reach conscious awareness
What is the attentional competing hypothees?
Early selection
attenuation
Late selection
What is early selection? Broadbent 1958
physical characteristics of messages used to select 1 message for further processing and all others are lost
What is attenuation? (Treisman, 1964)
physical characteristics used to select 1 message for full processing and other messages are given partial processing
What is late selection? (Deutsch & Deutsch, 1963)
all messages get through, but only one response can be made
What is inattentional blindness? (Mack & Rock, 1992, Simons & Chabris, 1999)
what we don’t attend to, we aren’t aware of
what is inattentional blindness a demonstration of?
attention is required for identification
What are the limits of attention?
change blindness
visual STM
what is change blindness?
can’t identify things without attending to them and attention is a limited resource. follows things might not be able to spot - changes between scenes unless attending to them
What is one way change blindness can bypass our ability to detect changes in luminance or motion?
Change blindness can occur by presenting an interleaving field (blank screen or distracting stimulus) between images, disrupting the detection of changes in luminance or motion (transients).
What did Rensinck (2000) find? CB
CB involves spotting transitions
CB suggests there’s failure in VSTM which enables us to compare between scenes (irrelevant for IB)
CB suggests might have limit in no. of items can hold in memory
What did Rensinck (2000) find? IB
IB involves identifying smth thats irrelevant to task
VSTM Luck and Vogel 1997
measured cap of VSTM (visual working memory)
1-12 colour patches shown for 100ms then blank 900 ms then shown again 2000 ms
one condition verbal load (make sure ppts not verbalising stimuli) Capacity limit of around 4 items
What do CB and change detection tasks show?
that there is a clear limit in info we can hold in VSTM
limit in what we can hold across a temproal gap
What are the limits of attention
limited in capacity
appears we can attend to a small number of area at same time
so our idea of what is incorrect
