Biomedical subjects

Karina J Linnell

Publications and source records attributed to Karina J Linnell.

4 recordsLinked to original sources

PubMed2005

Action modulates object-based selection.

Cueing attention to one part of an object can facilitate discrimination in another part (Experiment 1 [Duncan, J. (1984). Selective attention and the organization of visual information. Journal of Experimental Psychology: General, 113, 501-517]; [Egly, R., Driver, J., & Rafal, R. D. (1994). Shifting visual attention between objects and locations: evidence from normal and parietal lesion subjects. Journal of Experimental Psychology: Human Perception and Performance, 123, 161-177]). We show that this object-based mediation of attention is disrupted when a pointing movement is prepared to the cued part; when a pointing response is prepared to a part of an object, discrimination does not differ between (i) stimuli at locations in the same object but distant to the part where the pointing movement is programmed and (ii) stimuli at locations equidistant from the movement but outside the object (Experiment 2). This remains true even when the pointing movement cannot be performed without first coding the whole object (Experiment 3). Our results indicate that pointing either (i) emphasizes spatial selection at the expense of object-based selection, or (ii) changes the nature of the representation(s) mediating perceptual selection. In addition, the results indicate that there can be a distinct effect on attention of movement to a specific location, separate from the top-down cueing of attention to another position (Experiment 3). Our data highlight the interactivity between perception and action.

Adolescent↗

PubMed2004

Attentional selection of a peripheral ring overrules the central attentional bias.

In visual search, distractors that fall between fixation and the target are more disruptive than distractors that fall at the same eccentricity as the target (Wolfe, O'Neill, & Bennett, 1998). This sensitivity to the relative eccentricity of target and distractor elements originates from a space-based bias favoring stimuli closer to the fovea. We show that this spatial bias can be overruled by cuing attention to a ring-shaped object. We rule out various space-based explanations of these findings, including (1) attention to fronto-parallel planes in depth and (2) serial attention to different portions of a ring. We suggest that attentional selection of a ring-shaped object operates independently of, and can overrule, spatial biases in selection.

Adult↗

PubMed2002

Scene articulation: dependence of illuminant estimates on number of surfaces.

The ability of observers to detect changes in illuminant over two scenes containing different random samples of reflecting surfaces was determined in an experiment with Mondrian-like patterns containing different numbers of coloured patches. Performance was found to improve as the number of patches increased from 9 to 49. In principle, observers could have used space-average scene colour as the cue ('grey-world' hypothesis) or the colour of the brightest surface in the scene ('bright-is-white' hypothesis), as the two cues generally covary. In a second experiment, observers matched illuminants across different patterns in which the space-average cue and the brightest-patch cue were independently manipulated. The articulation of the patterns was varied: the number of patches increased from 49 (patch width 1 deg visual angle) to over 50000 (patch width 0.03 deg), while the gamut of colours was held constant. Space-average colour was found to be the dominant cue with all patterns except for those with the largest patches.

Color Perception↗

PubMed2002

Visual search within and across dimensions: a case for within-dimension grouping.

We used a visual search task in which participants searched for the presence of either both members or just one member of pairs of spatially separated simple visual features. Pairs of target features could be drawn either from within the same dimension (two colours, or two orientations) or from across two different dimensions (one colour and one orientation). In Experiment 1, display items carrying target and non-target features (target and distractor items respectively) were presented at interspersed spatial locations. Reaction times (RTs) to find both of two feature targets were generally slower than to find one feature target for within- and across-dimension target pairs alike. This slowing was approximately constant across display set sizes, with one exception: for within-dimension targets, two features could be detected as fast as single features when there were just two items in displays. Experiment 2 replicated the finding across all display set sizes when target items were always spatially adjacent rather than interspersed with distractor items. We interpret these data in terms of grouping between target features within the same dimension, and argue against there being any qualitative limit on visual processing or selection when target features come from a single dimension relative to when they come from separate dimensions.

Adult↗