PSYB51H3 Lecture Notes - Lecture 7: Visual Search, Horopter, Binding Problem

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PSYB51
October 29th, 2010
Lecture 7: Attention & Scene Perception
Short Answer Question:
1)
- You have a photoreceptor that might itself somehow contribute to colour
perception but alone is not colour-sensitive WKDWVEFWKHVLJQDOLV
DPELJXRXVGRQWNQRZZKDWH[DFWZDYHOHQJWKWKHLQFRPLQJOLJKWLV
- The problem of univariance is the fact that an infinite set of different
wavelength±intensity combinations can elicit exactly the same response from
a single type of photoreceptor. One photoreceptor type cannot make
accurate color discriminations based on wavelength.
- The solution LVWKDWZH¶YHPRUHWKDQRQHFRORXU-sensitive photoreceptor like
red, green and blue cones in our retinas. The combinations of the outputs of
these three types of cones ZLOODFWXDOO\WHOOXVZKDWFRORXUVZH¶UHORRNLQJDW
2)
- The location of objects whose images lie on corresponding points. The surface of
zero disparity.
6RWKLVLVDQDUHDZKHUHZHGRQ¶WKDYHdouble vision when we converge our eyes
on something.
- Attention can be directed at INPUTS, THOUGHTS & ACTIONS
- Able to process them & ignore other things
TOO MUCH arousal seems to activate all sorts of sensory inputs in a global way.
The person has problems concentrating as they will have problems ignoring things
that are irrelevant/ distracting.
We need attention
Both fecilatatory mechanisms (enhance & focus)
& inhibitory mechanism (ignore) will contribute
to what we call attention in multiple ways.
:H¶OOIRFXVRQDWWHQWLRQLQWKHYLVXDOGRPDLQ.
Arousal & Attention are clearly different things! But they do interact
with each other. The relationship between Arousal & attention ÆAs
arousal increases, the attention increases but further increases in
arousal could also bring about decreased attention.
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PSYB51
October 29th, 2010
- Bottlenecks: impossible to process HYHU\WKLQJ:HFDQt process all the
details. If we wanted to process everything that comes through our eyes ±
then our brain would have to be really big. Having too much brain is a
disadvantage ± b/c the brain is using a lot of energy relative to our body.
Definition of bottlenecks:
A bottleneck is a phenomenon where the performance or capacity of an entire system is limited
by a single or limited number of components or resources
So b/c there is a lack of brain LWVJRRGWRKDYHDWWHQWLRQ
- So these bottlenecks not only exist at a sensory level but also at a cognitive
level. For example, we can only have so many thoughts at the same time.
- But, there is also a motor bottleneck. Motor means having to do with our
output in terms of behaviour that involves muscle activity. So, this motor
bottleneck has to do with the fact that we have only 2 arms. More than 2
arms, like Goddess Lakshmiji has Æ She might (I know she does =]) then
actually have wider attention and ability in terms of motor activity b/c she
has more arms.
- Perceptual thresholds: OHVVXVHGDVLWVPRUHFRPSOLFDWHGSo how does
your threshold of perception change?
- Motor accuracy: being focused on action being performed
Attention helps us selecting one thing over the other. It helps us draw on what is important to us. So
something that helps us survive. So we use attention to focus on those things more important than
others (in terms of our survival) and we have certain heuristics to do that. Although we do make
mistakes with those heuristics! (e.g. car accidents)
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PSYB51
October 29th, 2010
- Brain activity: EUDLQDFWLYLW\FKDQJHVDVDIXQFWLRQRIZKHWKHU\RXUH
SD\LQJDWWHQWLRQYHUVXVZKHQ\RXUHQRW
- Eye movements and attention not completely connected
- Perceptual biases: how biases influence or reflect KRZZUHSD\LQJ
attention to
- In (c) on the slide: the cue is invalid not valid.
- Cue: A stimulus that might indicate where (or what) a subsequent stimulus
will be. Cues can be valid (correct information), invalid (incorrect), or neutral
(uninformative).
- 6RUHVSRQVHWLPHIDVWHUZKHQFXHLVYDOLGYHUVXVZKHQLWVLQYDOLGRUQHXWUDO
- Voluntary cues: use some kind of cognitive process and intentionally shift
attention in the respective direction.
SOA: depending on long you take to process the stimulus (cue)
In graph on slide: in voluntary cue (blue curve) Æ \RX¶UHDEOHWRNHHS\RXU
attention there for a longer time so the blue curve stays higher than the red curve
(stimulus cue Æ automatic fashion) which later declines [so the benefits of the
stimulus cue dip down as you go further along the SOA on the x-axis Æ this
decline is known as IOR]
Natural Biases:
- We tend to pay attention more to one side than to the other although we are
able to pay attention to both sides
- Brain being asymmetrical: Face processing is more on the right
hemisphere while language processing is more in the left hemisphere Æ that
will bias our attention in one or the other way. So, there is no particular
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