Abstract
Purpose: In the past twenty five years visual attention has been described in terms of varied metaphors, among which a spotlight, a zoom lens and a gradient field. An essential aspect of all these metaphors is the distribution of attentional resources in the visual field, which is not necessarily determined by the fixation point, and may depend on both external events and internal mental processes. This study presents a novel approach, using geostatistical analysis, to investigate how visual attention is allocated in continuous regions of space by measuring simple reaction times (SRTs) of subjects under different task requirements.
Methods: SRTs to visual stimuli were measured in ten young subjects (27.1±6.8years). Stimuli and SRTs were provided by the software E–Prime v 1.1 (PST Inc.) using a 17’ monitor driven by a Matrox P650 graphics board (refresh rate 100 Hz, resolution of 800 x 600). Five different situations were employed: in experiment 1 participants were asked not to attend to any particular region, but rather try to spread their attention as uniformly as possible over the computer screen (diffuse attention). In the remaining experiments, participants were instructed to direct their visual attention covertly to the center (exp. 2), to the left (exp. 3), to the right (exp. 4) or to both right and left (but not to the center, thus characterizing a divided attention situation – exp. 5). Data were analyzed with the software Idrisi – Kilimanjaro v. 14.2 – Clark Labs – with Gstat geostatistical module.
Results: The isoline maps obtained through the geostatistical analysis show much structure, superposed on which there is a general tendency towards shorter times to the left in exp. 3, to the right in exp. 4, and distributed to both right and left (even though not as lateralized as in the previous two experiments) in exp. 5. One–way ANOVA showed that the RTs of experiment 2 were overall faster than those of experiments 3, 4 and 5 (F = 11.56, p<0.001).
Conclusions: The results indicates the potential application of geostatistical methods in the study of the spatial distribution of visual attention in normal subjects, opening potential applications to some pathological conditions such as Attention Deficit Hyperactivity Disorder.
