PSYC 213 Lecture Notes - Change Blindness, Microsoft Powerpoint, Saccade
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It is possible to become functionally blind to certain parts of our visual field if we are paying close
attention to something else. This is called change blindness. Most people are confident, however, that
they would not be fooled by changes in their visual field, which has been called the illusion of memory.
What is attention?
There is no clear-cut definition. It is something like the zoning in of our processing abilities on specific
pieces of information; when we consciously direct our attention, it is effortful.
We have three basic states when we are awake:
Attentive, inattentive (drowsy/relaxed), and automatic. The attentive state of mind consists of attending
consciously to certain things while ignoring others.
William James gave his take on what attention is in 1890. See slide 6 of the attention power point.
Harold Pashler also gave his own attempt in his book in 1998, same slide.
How do we attempt to define attention?
We can try to represent attention through metaphors:
–Michael Posner (very important attention-psychologist) thought of attention as a spotlight; he
proposed that attention, just like a light, can be turned on or off and directed to different places.
–Eriksen proposed a similar idea; a zoomlens. He simply added that there are gradients of
attention. Things in the “periphery” of attention are less processed than things in the “middle”.
Everything in the spotlight is processed vs everything in the spotlight is processed to varying degrees
Properties of attention:
1) Attention is selective: only a few things can be attended to. Only a few portion of sensory inputs
are attended to at any given moment; at every passing waking moment, we are bombarded by
sensory stimuli (auditory, tactile, visual, etc.), but we don't pay attention to them.
2) Attention has a limited capacity: it is very difficult to attend to two things at once. Example:
people are given the task to read a story while copying dictated words. Performance was really
bad, even though people improved at switching from one process to the other.
When does attention act in the different stages of processing?
Stimuli -> Registration -> Perceptual analysis -> Semantic analysis -> Response
There are two main ideas proposing where attention comes into play. The “early filter” proposes that
attention will act during perceptual analysis; it will filter everything that is perceived but not attended
to, not allowing us to process at a these things at a higher level. The “late filter” proposes that attention
filters at the semantic analysis level. Both models are proved and disproved by experiments.
For instance, when people are asked to attend to (and repeat) a stimulus arriving into one ear
while ignoring a stimulus being presented to the other ear, people are completely incapable of noticing
if the unattended stimulus's text makes sense on a semantic level (i.e. People can hear complete
nonsense and not notice, they will only notice if there is very low-level changes in the stimulus like a
change of voice, or if the person's voice is said).
An example that goes against the idea of an early filter and rather supports a late filter is the
Stroop effect. The meaning of the written word interferes with the task of saying what the colour of the
word is. E.g.: blue written in red is hard to identify as “red”, the meaning of the word creates
inteference, even if the word is not attended to.
Personal idea: could it be that perceptual and semantic analysis are more or less simultaneous
instead of being serial?
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