Afroditi Panagopoulos

Attentive mechanisms in visual search.

Selective attention can be employed to a restricted region in space or to specific objects. Many properties of this attentional window or spotlight are not well understood. In the present study, we examined the question whether the putative shape of the attentional spotlight can be determined by endogenous cueing within a visual search paradigm. Participants searched for a target among distractors, which were arranged within a vertical or horizontal rectangle. The shape of this rectangle was cued endogenously in a valid or invalid way. Response times (RTs) to correct identification of target orientation were recorded. In Experiment 1, the difference between valid and invalid RTs demonstrated that cueing resulted in elongated attentional areas. This was true only for a group of experienced psychophysical participants, whereas a group of inexperienced participants were not able to use cueing in this way. In Experiment 2, the line motion illusion was used to examine the spatial properties of the attended area. The results confirmed for both experienced and inexperienced participants that attention was confined to the cued elongated area only. We present converging evidence for an attentional spotlight whose shape can be adjusted flexibly by appropriate endogenous cueing.

Características atentivas reveladas por dicas múltiplas locais e globais

The characteristics of the attentive focus were investigated through the effect of local and global multiple cues, multiple and unitary, on the performance of a visual search task. The results show a gain in the performance of tests with valid multiple local cues; the gain is proportional to the size of the area in which the stimuli are presented. In the tests with valid local tips for the area there is a gain when the stimuli are presented in the larger area and a cost in the smaller area. Global cues do not generate a gain in tests with valid cues but are followed by a cost in tests with invalid cues. There is also a cost in tests where the attentive focus must be expanded or contracted. The results suggest that the model of multiple attentive focuses is more adequate to explain performance in tests with multiple local cues.

Distribution of visual attention within a cued area: evidence based on temporal order judgments

Three experiments were performed to investigate the distribution of attention across the visual field and the possibility of attentional resources to be more concentrated inside an abrupt onset frame (cue). The participants performed a temporal order judgment task of two letters presented in sequence; one letter presented inside and the other outside the frame. The results showed that the information presented inside the frame had its perceptual latency shortened in relation to the information presented outside the frame in experimental conditions where the frame orientation, the distance between the two letters and the cue onset time were manipulated. The advantage of the information presented inside the frame was attributed to the displacement of attention to the area delimited by the frame. The results contribute to the understanding of visual perception, showing that attentional resources may be redistributed inside the borders of a geometric figure.