A developmental study of visual filtering : can windows facilitate filtering efficiency?

A forced-choice reaction time (RT) task was used to examine the development of visual filtering. Specifically, this study examined whether visual filtering is more efficient in smaller spatial ranges, and the extent to which age-related changes in filtering efficiency could be attributed to improvements in the ability to expand and contract an attentional focus. Participants included 20 children in each of four age groups (4, 5, 7, and 9 years), as well as 20 adults aged between 20 and 29 years. Conditions varied with regard to the location or presence of distracters, and the presence of a window within which target stimuli were presented. RT's were slower in the presence of distracters located within one 1 degree of visual angle from target stimuli than when distracters were presented 5.7 degree of visual angle away. In addition, young children were less capable than either older children or adults to filter task-irrelevant stimuli. With regard to the window, RT's were faster in the presence of a window than in its absence. Finally, the window was most effective in improving the filtering efficiency of 4 year old children. These results are discussed in terms of the zoom-lens metaphor of visual attention, and the development of the ability to vary the size of an attentive zoom-lens in response to task requirements