scholarly journals Early vision and visual attention

Psihologija ◽  
2003 ◽  
Vol 36 (3) ◽  
pp. 241-254
Author(s):  
Vasilije Gvozdenovic
Keyword(s):  
Visual Search ◽  
Visual Perception ◽  
Visual Attention ◽  
Cognitive Processes ◽  
Feature Integration ◽  
Integration Theory ◽  
Early Vision ◽  
Scientific Approach ◽  
Feature Integration Theory

The question whether visual perception is spontaneous, sudden or is running through several phases, mediated by higher cognitive processes, was raised ever since the early work of Gestalt psychologists. In the early 1980s, Treisman proposed the feature integration theory of attention (FIT), based on the findings of neuroscience. Soon after publishing her theory a new scientific approach appeared investigating several visual perception phenomena. The most widely researched were the key constructs of FIT, like types of visual search and the role of the attention. The following review describes the main studies of early vision and visual attention.

scholarly journals Visual Search for Feature and Conjunction Targets with an Attention Deficit

1993 ◽  
Vol 5 (4) ◽  
pp. 436-452 ◽  
Author(s):  
Martin Arguin ◽  
Yves Joanette ◽  
Patrick Cavanagh
Keyword(s):  
Visual Search ◽  
Visual Attention ◽  
Attention Deficit ◽  
Feature Integration ◽  
Integration Theory ◽  
Target Orientation ◽  
Search Tasks ◽  
Attention Disorder ◽  
Feature Target ◽  
Marked Deficit

Brain-damaged subjects who had previously been identified as suffering from a visual attention deficit for contralesional stimulation were tested on a series of visual search tasks. The experiments examined the hypothesis that the processing of single features is preattentive but that feature integration, necessary for the correct perception of conjunctions of features, requires attention (Treisman & Gelade, 1980 Treisman & Sato, 1990). Subjects searched for a feature target (orientation or color) or for a conjunction target (orientation and color) in unilateral displays in which the number of items presented was variable. Ocular fixation was controlled so that trials on which eye movements occurred were cancelled. While brain-damaged subjects with a visual attention disorder (VAD subjects) performed similarly to normal controls in feature search tasks, they showed a marked deficit in conjunction search. Specifically, VAD subjects exhibited an important reduction of their serial search rates for a conjunction target with contralesional displays. In support of Treisman's feature integration theory, a visual attention deficit leads to a marked impairment in feature integration whereas it does not appear to affect feature encoding.

scholarly journals Perception of illusory contour figures: Microgenetic analysis

Psihologija ◽  
2004 ◽  
Vol 37 (4) ◽  
pp. 451-481 ◽  
Author(s):  
Vasilije Gvozdenovic
Keyword(s):  
Visual Search ◽  
Visual Attention ◽  
Illusory Contour ◽  
Feature Binding ◽  
Integration Theory ◽  
Search Tasks ◽  
Time Period ◽  
Priming Phase ◽  
Feature Integration Theory ◽  
Two Phases

Microgenetic analysis was used to investigate perception of illusory contour figures which represent whole, completed forms on the basis of segmented, incomplete stimulation. The analysis provided an experimental approach to this phenomenon which was standardly investigated phenomenologically. Experimental procedure consisted of two phases: a) priming phase and b) test phase which consisted of visual search task. Two types of visual search tasks were applied: (i) classic detection, in which subjects were detecting presence or absence of the target stimuli and (ii) two-alternative forced choice, 2AFC, in which subjects performed discrimination between two concurrent targets (target A vs. target B). Variation of exposition of prim stimuli was used as an indication of the percept formation period. Concepts like early vision, visual attention and feature binding were investigated. Four experiments were conducted. Their outcome showed that (i) perception of amodal figure requires visual attention, (ii) features binding precedes spatial attention and (iii) time period of percept formation is dependent of task properties and varies between 50 - 150 ms. Some results obtained in this research could be explained by feature-integration theory (Treisman & Gelade, 1980; Treisman, 1986). Furthermore, percept formation period data comply with data acquired in Elliott & M?ller's psychophysical research (1998).

Distractor Ratio and Grouping Processes in Visual Conjunction Search

Perception ◽  
1992 ◽  
Vol 21 (1) ◽  
pp. 21-38 ◽  
Author(s):  
Marie E Poisson ◽  
Frances Wilkinson
Keyword(s):  
Search Strategy ◽  
Conjunction Search ◽  
Integration Theory ◽  
Distractor Type ◽  
Fixed Size ◽  
Single Feature ◽  
Search Processes ◽  
Cast Doubt ◽  
Feature Integration Theory

According to feature integration theory, conjunction search is conducted via a serial self-terminating search. However, effects attributed to search processes operating on the entire display may actually reflect search restricted to elements defined by a single feature. In experiment 1 this question is addressed in a reaction-time (RT) paradigm by varying distractor ratios within an array of fixed size. For trials in which the target was present in the array, RT functions were roughly symmetric, the shortest RTs being for extreme distractor ratios, and the longest RTs being for arrays in which there were an equal number of each distractor type. This result is superficially consistent with Zohary and Hochstein's interpretation that subjects search for only one distractor type and are able to switch search strategy from trial to trial. However, negative-trial data from experiment 1 cast doubt on this interpretation. In experiment 2 the possible role of ‘pop out’ and of distractor grouping in visual conjunction search is investigated. Results of experiment 2 suggest that grouping may play a more important role than does distractor ratio, and point to the importance of the spatial layout of the target and of the distractor elements in visual conjunction search. Results of experiment 2 also provide clear evidence that groups of spatially adjacent homogeneous elements may be processed as a unit.

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