Abstract
Covert attention is the ability to select a certain location of the visual field, without eye or head movements, and give it priority in perceptual processing (Carrasco et al. 2002).
In a series of experiments we measured RTs in both overt and covert attention tasks and data were analyzed through geostatistical methods.
In Experiment 1 participants oriented their attention to the center of the screen coincident with the fixation point (overt attention). We showed that participants indeed focused their attention toward the center of the screen, with spatial distribution similar to the topography of cone distribution of the human retina (Curcio et al. 1990).
Experiments 2 and 3 were designed to assess the spatial patterns of covert attention to left and right, respectively. Results showed that participants were able to direct attentional focus away from their gaze and toward areas of the computer screen they should attend, thus characterizing covert attention. The focus of attention on the left hemi-field, i.e. right hemisphere (experiment 2) was more evident than the contra-lateral experiment, these data are consistent with hemispheric asymmetries reported in the literature.
Surprisingly, in both experiments 2 and 3 there was an almost symmetrical contra-lateral facilitation (slightly displaced upward). This facilitation was not as evident as the focus of covert attention, but was clearly distinguishable from the surroundings. These results suggest a top-down inter-hemispheric modulation of attention, which is more evident in the right hemisphere. Here a “spotlight reflection” metaphor is proposed to describe this phenomenon.
CNPq Grant # 141951/2002-8 / FAPESP Grant # 04/07963-0 / IBRO Travel Grant