Biomedical subjects

L Shalev

Publications and source records attributed to L Shalev.

3 recordsLinked to original sources

PubMed2000

Stroop and Garner effects in and out of Posner's beam: reconciling two conceptions of selective attention.

Space- or object-based models, on the one hand, and structural-informational models, on the other hand, reflect conceptually distinct approaches to visual selective attention. In 3 studies, the authors contrasted these approaches by jointly applying prototypical routines prescribed in each approach. Following a space-based paradigm developed by M. I. Posner, participants were cued to attend to a certain spatial location, and performance at expected and unexpected locations was compared. Following a structural paradigm developed by W. R. Garner, the targets were color words printed in various colors, and the participants responded to either the color or the word component of the stimulus. Performance was poorer at unexpected than at expected locations. However, comparable amounts of Stroop and Garner interference affected performance at both expected and unexpected locations. It is suggested that the processes that govern (a) input selection from the visual field and (b) dimensional selection from the stimulus reflect fundamentally different systems of attention.

Attention↗

PubMed1996

Inattention magnifies perceived length: the attentional receptive field hypothesis.

Five experiments demonstrated that a briefly presented vertical line is judged as longer when it is unattended relative to when it is attended. This effect was obtained in estimating the length of 1 of 5 possible lines (Experiment 1) and in matching the length of a test line to a criterion line (Experiments 3 and 4). The directional effect of attention was eliminated when participants estimated the length difference between 2 simultaneously presented lines (Experiment 2). An additional matching experiment (Experiment 5) demonstrated similar lengthening effects for unattended lines and for unattended distances separated by vertically displaced dots. It is proposed that the metric for unattended stimuli is composed of large attentional receptive fields and that the final output is mediated by rounding up processes, so that the unattended line is systematically perceived as longer than the attended one.

Attention↗

PubMed1994

Attention reduces perceived brightness contrast.

The effects of attention on brightness perception was investigated in four experiments. In the first three, subjects estimated the brightness of a briefly presented small grey square by selecting a number that corresponded to one of four possible squares varying on a lightness-darkness dimension. In the last experiment, subjects matched the brightness of two peripheral squares, one attended and one unattended. When the stimulus appeared on a white background (Experiments 1, 2, and 4a) it was judged as brighter when attention was directed to its location than when attention was diverted to another location. When the stimulus appeared on a dark background (Experiments 3 and 4b), the opposite pattern of results was obtained: the attended stimulus was judged as darker than the unattended one. These results show that attention reduces the perceived contrast between the stimulus and its background, suggesting that attention enables subjects to provide a more veridical judgement of stimulus brightness by limiting processing resources to the square itself, at the expense of the surrounding background. As attention produced a directional brightness effect rather than just an improvement in report accuracy, the results can be attributed to early perceptual processing effects, hence providing support for early selection views of attention.

Adult↗