Biomedical subjects

Fook K Chua

Publications and source records attributed to Fook K Chua.

3 recordsLinked to original sources

PubMed2005

The effect of target contrast on the attentional blink.

In this set of five rapid serial visual presentation experiments, observers identified one or two target letters that were embedded in a stream of distractors. Target contrasts were varied, and their effects on the attentional blink (AB) were examined. Target identification improved when its contrast was increased. But whereas an increase in the first target's (T1) contrast facilitated its identification, the recovery of the second target (T2) was paradoxically hampered (Experiments 2 and 5). Similarly, identification of the target suffered when the preceding singleton's contrast was increased (Experiment 1). The AB was eliminated by inserting a blank after a low-contrast, but not a high-contrast, T1 (Experiment 5). Increasing T2's contrast attenuated the blink (Experiment 3) and compensated the larger AB caused by a high-contrast T1 (Experiment 4). In all, these results showed that attention continued to be engaged as long as the target's contrast prolonged its perceptibility. When the high-contrast target was T1, a larger AB was produced; when it was T2, there was protection from substitution masking.

Attention↗

PubMed2004

Capturing attention when attention blinks.

Four experiments addressed the question of whether attention may be captured when the visual system is in the midst of an attentional blink (AB). Participants identified 2 target letters embedded among distractor letters in a rapid serial visual presentation sequence. In some trials, a square frame was inserted between the targets; as the only geometric object in the sequence, it constituted a singleton. Capture effects obtained when the AB was most severe and when it was over were compared. There were 3 main results. First, capture occurred even when the AB was crippling, suggesting that a singleton exogenously engaged attention even when processing of a previous target was continuing apace. Second, when the singleton contained the key target feature, capture effects were clearly manifest. Third, even when the singleton did not possess the key target feature, it still succeeded in capturing attention, although the effects were both feeble and fleeting.

Attention↗

PubMed2003

Grouping with and without attention.

The effects of perceptual grouping on a line discrimination task were investigated using Moore and Egeth's (1997) paradigm. Observers judged which of two lines, presented one above the other over a matrix of spots, was longer. On some trials, larger spots at both ends of the lines formed arrowheads, thereby making possible the Müller-Lyer illusion. When observers attended only to the lines, they were not aware of the arrowheads. Yet their line judgment performance showed that they had succumbed to the illusion. When the observers' attention was directed to the arrowheads but they nevertheless failed to discern the arrowheads' orientation, their line judgments were still influenced by the illusion.

Attention↗