Stimuli selection and attentive analysis in the visual search task: evidences of discrete and sequential stages

Abstract

To find a specific object among many others in the environment is one of the most common actions of our daily life. In accordance with Neisser (1) , the selection of the relevant information in the environment involves two moments: a pre-attentive analysis that performs simple operations on great areas of the visual field, and an attentive analysis that performs complex operations on restricted areas of the field. Treisman and her colleagues (2,3) had applied this idea to the study of the visual information processing. In accordance with her feature integration theory, the selection of an object in the visual field depends on the features of the object and on the features of other objects in the field. The information on the visual features of objects is codified in retinotopic maps, specific to each feature, and independent from each other.The feature maps will codify information through operations carried out simultaneously on great areas of the visual field. Each map codifies only the presence of a specific feature in the visual field, either the color, the size, or the orientation. It informs nothing on the other features, on the position that the feature occupies in the space, or on the identity of the object in which the feature is present. The positions of objects, but not their features or their identities, are codified in a localization map. An object that has only one feature that differentiates it from all other objects present in the field will be selected in a fast and efficient way after an analysis carried out in parallel in the specific feature map. For example, a red vertical line will popout, that is, it will be detected very quickly when it is located among black It is largely accepted that only a few stimuli will be selected and attentively analyzed in a difficult visual search task, but the efficiency of the selection process remains unclear. The present study shows that the processes of selection and analysis are affected by different experimental factors, which contribute additively to the RT. The RT increases as a function of the target-distractor similarity and, as a function of the presence of the background stimuli in the search field. In the target present trials, the presence of the background stimuli increases the RT in 30 ms, independent of target-distractor similarity. In the target absent trials, the effect of the background stimuli is inversely related to target-distractor similarity. The increase in similarity between target and distractor can lead to an increase in the ratio of guessing, compensating or eliminating the increase in RT caused by the presence of the background stimuli. These results are compatible with a model in which the relevant stimuli are selected preattentively and then, submitted to an attentive serial analysis.

Seleção e análise de estímulos na tarefa de busca visual

“…Esses resultados têm mostrado que a eficácia da busca visual não é prejudicada pela presença da textura, desde que esta seja suficientemente distinta dos estímulos relevantes em, pelo menos, uma característica visual importante, tal como a luminância (Galera, 1997(Galera, , 2001(Galera, , 2003Galera, Lopes & von Grünau, 2000). Nesse caso, a presença da textura não altera a taxa de busca (β) da função TR, permitindo supor que a textura foi eliminada do processo de análise.…”