PSYC 2650 Chapter 4: Chapter 4

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16 Nov 2017
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Recognition: Some Early Considerations
Variations in “stimulus input” provides our first indication that object recognition
involves some complexity
Our recognition of various objects is influenced by the context in which the
objects are encountered
Object recognition is also influenced by the stimulus itself
Bottom-up processes: processes that are directly shaped by the stimulus (also
called data driven)
Top-down processes: processes shaped by relying on knowledge (also called
concept driven)
The Importance of Features
Recognition might begin with the identification of visual features in the input
pattern the vertical lines, curves, diagonals, and so on
o You can then start assembling larger units
People are remarkably efficient when searching for a target defined by a simple
feature
o E.g., finding a green shape in a field of red shapes
People are much slower in searching for a target defined as a combination of
features
Damage to the parietal cortex: integrative agnosia
o Appear relatively normal in tasks requiring them simply to detect features
in display
o Impaired in tasks that require them to judge how the features are bound
together to form complex objects
Word Recognition
Once detection has occurred, separate mechanisms are needed to put the
features together, assembling them into complete objects
Factors Influencing Recognition
Tahistoscope: a device specifically designed to present stimuli for precisely
controlled amounts of time
Each stimulus if followed by a post stimulus mask just a random jumble of
letters
o Serves to interrupt any continued processing that participants might try to
do for the stimulus just presented
o Researchers can be certain that a stimulus presented for (e.g.,) 20ms is
visible for exactly 20ms and no longer
If the stimulus is a word, we can measure familiarity by counting how often that
word appears in print, and these counts are an excellent predictor of
tachistoscopic recognition
Another factor is recency of view
o If you view a word and then a little later view it again, they will recognise
the word much more readily the second time around
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