Biomedical subjects

A Gellatly

Publications and source records attributed to A Gellatly.

5 recordsLinked to original sources

PubMed2001

Effect of object onset on the distribution of visual attention.

There now exists considerable evidence to suggest that the appearance of a new object in the visual field captures visual attention. One of the consequences of this attentional capture is that the object initiates a redistribution of attentional resources across visual space. This is classically observed in the precuing paradigm in which the onset of an abrupt cue influences the processing of a subsequently presented target. The present research describes a new phenomenon that occurs as a result of a new object appearing in the visual field. A stimulus presented in a region of space adjacent to a corner of an onsetting object receives an enhancement of processing relative to a stimulus presented adjacent to one of the object's straight edges. With the use of 2 converging methods, evidence is presented that suggests that the effect is a higher order attentional phenomenon whereby greater resources become directed to the corners of objects.

Attention↗

PubMed2000

Accuracy of target detection in new-object and old-object displays.

In 4 experiments, the authors investigated accuracy of detecting a target among nontargets. In some experiments, the target was a second-order square of stationary lines on a background of downward-moving lines, and nontargets were second-order squares of upward-moving lines. In other experiments, target and nontarget squares and background were shades of gray. The principal comparison was between "new" and "old" object displays. In new-object displays, search items appeared abruptly and one might be a target. In old-object displays, search items appeared abruptly, and after a delay one might become a target. Search displays in both conditions terminated shortly after target onset. Except when target onset was associated with the sole luminance change in a display, targets were much better detected in new- than in old-object displays. It is suggested that object onsets elicit a brief stimulus-driven enhancement of attention to the new objects.

Attention↗

PubMed1999

Do equiluminant object onsets capture visual attention?

S. Yantis and A. P. Hillstrom (1994) have claimed that abrupt onset of a new visual object captures attention even when the new object is equiluminant with its background, implying that attention is captured at the level of object descriptions rather than at the level of luminance change detection. S. Yantis and A. P. Hillstrom's experiments contained potential flaws that call their conclusion into question. The present article reports 5 experiments investigating these and related issues. The results suggest that for abruptly onsetting visual objects to capture attention, detection of change in a dimension of sensory stimulation is a necessary, but perhaps not a sufficient, requirement. Evidence is also presented against the view that attentional priority for new objects arises as a result of visual masking of old objects in the same displays.

Adult↗

PubMed1997

The experience and expression of pain in Alzheimer patients.

OBJECTIVES: to establish whether there is a sub-group of patients suffering from senile dementia, Alzheimer-type (SDAT), who have ceased to undergo normal experience of pain. METHODS: two single case studies are briefly described and a small-scale national survey by questionnaire is reported. RESULTS: combining the original two cases with those garnered from the survey yielded 49 cases of SDAT patients who failed to exhibit normal experience of pain. In none of the cases does there seem to have been any particular problem of emotional expression or of verbal communication, but pain reactions to accidents, surgical procedures, infections and pre-existing conditions seem to have been extinguished. CONCLUSIONS: such patients may form a theoretically interesting sub-group with particular neuroanatomical pathology. Recognition of the existence of such a group has important legal and ethical implications for those treating or caring for patients of this kind.

Aged↗

PubMed1995

Attentional tracking in the perception of apparent motion: evidence from sequential blanking displays.

Perception of sequential blanking displays was studied in a series of three experiments investigating factors that influence whether "shadow motion" or "item motion" is seen in a display. In addition to the duration of the blanking interval (BI) itself, three other such factors were identified: the eccentricity at which the display is viewed, the spacing of items in the display, and the type of motion that subjects are instructed to try to see. It is argued that these and other previously reported results are explicable without the need to invoke any kind of visual integration period. Instead, they are interpreted in terms of a first-order system of automatic luminance detectors and a second-order tracking system involving both voluntary and involuntary attention. The relationship of these findings to other recent work in apparent motion and visual attention and to other bistable motion displays is discussed.

Attention↗