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Wednesday, December 22, 2010

NON-VISUAL KNOWLEDGE AND PERCEPTUAL SET NON-VISUAL KNOWLEDGE AND PERCEPTUAL SET

Perceptual assumptions about lighting and noses are probably common to all humans. But there are other kinds of knowledge affecting perception which depend on linguistic, graphic and other cultural conventions. The central symbol A is perceived as ‘B’ if the vertical set of symbols is scanned, and as ‘13’ if the horizontal set of symbols in scanned. Similarly, the central letter in the two words is perceived as an ‘H’ when reading the first word, and as an ‘A’ when reading the second. Such effects depend on knowledge of a particular set of alpha-numeric conventions and of the graphology of the English language (and so would presumably not be experienced by someone who spoke and wrote only Arabic). They illustrate that non-visual knowledge can be important in visual perception. There are other situations in which the role of past experience and verbal clues become apparent.

But consider the clues ‘leaves and a Dalmation dog’, and you will probably see the dog nosing among the leaves almost instantly. Similarly, the pictures have been transformed into black blocks and black lines, so that the identity of the objects they represent may not be obvious. But again, verbal clues such as ‘elephant’, ‘aeroplane’ or ‘typewriter’ are often sufficient for the observer to identify the objects. Interestingly, once you perceive the Dalmation and the elephant, it is impossible to look at the pictures again without seeing them. These effects are sometimes described as examples of perceptual set: the verbal clues have somehow ‘set’, or programmed, the individual to interpret or perceptually organize ambiguous or impoverished stimuli in a certain way.

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