Based on findings from parallel search and conjunction search tasks, Treisman and colleagues put forward a theory – the feature integration theory [feature integration theory different features of an object (e.g. colour, orientation, direction of motion) are thought to be analysed separately (and in parallel) by several distinct mechanisms, and the role of attention is to ‘glue together’ these separate features to form a coherent representation] – which sought to explain the early stages of object perception. This theory has become very influential (Treisman & Gelade, 1980; Treisman & Schmidt, 1982). These authors suggested that the individual features that make up an object (its colour, motion, orientation, and so on) are encoded separately and in parallel by pre-attentive cognitive mechanisms. However, in order to perceive a whole object, the observer needs to ‘glue together’ (or integrate) these separate features, using visual attention. One interesting prediction from the theory (which has been borne out y experiments) is that, if attention is diverted during a conjunction search task, there would be nothing to hold the features of an object together, and they could then change location to join inappropriately with features of other objects. For example, if observers are distracted by requiring them to identify two digits during the presentation of a display , they often report seeing dollar signs, even though the S and the straight line which make up the sign are never in the same location. It is as though, preattentively, the S and the parallel lines are ‘free-floating’ and are able to combine to present objects that are not physically in the display. These so-called illusory conjunctions [illusory conjunctions perceptual phenomena which may occur when several different stimuli are presented simultaneously to an observer whose attention has been diverted (e.g. the perception of a red cross and a green circle when a red circle and a green cross are presented)] provide support for feat re integration theory (Treisman & Schmidt, 1982; Treisman, 1986).
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Wednesday, December 22, 2010
Feature integration theory
Based on findings from parallel search and conjunction search tasks, Treisman and colleagues put forward a theory – the feature integration theory [feature integration theory different features of an object (e.g. colour, orientation, direction of motion) are thought to be analysed separately (and in parallel) by several distinct mechanisms, and the role of attention is to ‘glue together’ these separate features to form a coherent representation] – which sought to explain the early stages of object perception. This theory has become very influential (Treisman & Gelade, 1980; Treisman & Schmidt, 1982). These authors suggested that the individual features that make up an object (its colour, motion, orientation, and so on) are encoded separately and in parallel by pre-attentive cognitive mechanisms. However, in order to perceive a whole object, the observer needs to ‘glue together’ (or integrate) these separate features, using visual attention. One interesting prediction from the theory (which has been borne out y experiments) is that, if attention is diverted during a conjunction search task, there would be nothing to hold the features of an object together, and they could then change location to join inappropriately with features of other objects. For example, if observers are distracted by requiring them to identify two digits during the presentation of a display , they often report seeing dollar signs, even though the S and the straight line which make up the sign are never in the same location. It is as though, preattentively, the S and the parallel lines are ‘free-floating’ and are able to combine to present objects that are not physically in the display. These so-called illusory conjunctions [illusory conjunctions perceptual phenomena which may occur when several different stimuli are presented simultaneously to an observer whose attention has been diverted (e.g. the perception of a red cross and a green circle when a red circle and a green cross are presented)] provide support for feat re integration theory (Treisman & Schmidt, 1982; Treisman, 1986).
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