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Liat Goldfarb, Anne Treisman; How is quantity bound to specific objects?. Journal of Vision 2009;9(8):811. doi: 10.1167/9.8.811.
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At an early stage of perception, simple features of the scenery such as colors or shapes are processed separately. Each feature processing (e.g.: color) can be performed independently from the processing of other features (e.g.: shape), (e.g., Treisman & Gelade, 1980; Treisman & Schmidt,1982). Numbers or quantities also appear in all kinds of natural scenes and potentially can be perceived as such. A scene that contains for example 2 cups and 4 plates can theoretically activate in the observer's brain the quantities “2” and “4”. In contrast to other features such as colors or shapes, the information “2” and “4” depends partly on the processing of other features (e.g.: if we fail to distinguish between the shape of a plate and the shape of a cup, we are also unlikely to perceive the quantity “2” or “4” ). Does this make the processing of feature quantity special?
To address this question we performed fMRI experiments using the adaptation technique and examined three hypotheses concerning the way feature quantity is represented. Hypothesis-1: simple features are processed separately. Accordingly, only the number area identifies the specific quantity of each feature (e.g.: the number area is activated by the appearance of the quantities “2” and “4”). Hypothesis-2: the specific feature area identifies also the quantity of each feature; since no other area needs to be sensitive to the specific quantity of each feature, the number area is not sensitive to this kind of information. It identifies only the overall number of objects. Hypothesis-3: feature quantity is unique- it is represented twice: once in the number area and once in the specific feature area.
The results from the current fMRI study in which participants adapted to different numbers of letters (Experiment 1) and of faces (Experiment 2) best fit this last interesting hypothesis.
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