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PubMed2003

Contrasting effects of sensory limits and capacity limits in visual selective attention.

The effects of perceptual load and those of target-stimulus degradation on distractor processing were contrasted. Targets either had to be found among several nontargets (high perceptual load) or were presented alone and were intact (low perceptual load), had reduced size and contrast (Experiment 1), had reduced duration and were followed by a mask (Experiment 2), or had reduced visual acuity owing to position eccentricity (Experiment 3) in the degraded low-load condition. The results showed that both high perceptual load and target degradation increased general task difficulty, as is reflected by overall reaction times and accuracy. However, whereas high perceptual load reduced response-competition effects of irrelevant distractors, target degradation increased distractor effects. These results support the hypothesis that distractor processing depends on the extent to which high perceptual load exhausts attention in relevant processing and provide a dissociation between perceptual load and general task difficulty and processing speed.

Attention↗
PubMed1993

Limits on the limitations of context-conditioned effects in the perception of [b] and [w].

We investigated the conditions under which the [b]-[w] contrast is processed in a context-dependent manner, specifically in relation to syllable duration. In an earlier paper, Miller and Liberman (1979) demonstrated that when listeners use transition duration to differentiate [b] from [w], they treat it in relation to the duration of the syllable: As syllables from a [ba]-[wa] series varying in transition duration become longer, so, too, does the transition duration at the [b]-[w] perceptual boundary. In a subsequent paper, Shinn, Blumstein, and Jongman (1985) questioned the generality of this finding by showing that the effect of syllable duration is eliminated for [ba]-[wa] stimuli that are less schematic than those used by Miller and Liberman. In the present investigation, we demonstrated that when these "more natural" stimuli are presented in a multi-talker babble noise instead of in quiet (as was done by Shinn et al.), the syllable-duration effect emerges. Our findings suggest that the syllable-duration effect in particular, and context effects in general, may play a more important role in speech perception than Shinn et al. suggested.

Adult↗
PubMed2004

Mammography screening in Switzerland: limited evidence from limited data.

QUESTIONS UNDER STUDY: In Switzerland controversy exists on how to summarise the evidence on the efficacy and effectiveness, as well as adverse effects, of mammography screening, and breast cancer mortality trends are often discussed in the context of the impact of mammography. PRINCIPLES/METHODS: Single-study publications, meta-analyses, and reports by international expert groups on mammography screening are reviewed. Breast cancer mortality trends from 1970-2000 are reported and discussed in the context of the Swiss screening situation. RESULTS: In Switzerland breast cancer mortality rates for female Swiss nationals aged 50-79 years fell between 1990 and 2000 by some 25% in all language regions. The data from randomised studies in large populations in several countries with well organised mammography programmes prompt the conclusion that participation in organised screening programmes with rigorous quality standards reduces breast cancer mortality. The achievable long-term reduction in breast cancer mortality ranges from 5-20% in the target population provided that appropriate diagnostic investigation and treatment are available. To achieve this in Switzerland 830 to 3300 women need to be invited to screening for ten years to prevent one death from breast cancer. The risk-benefit profile of mammography screening is likely to be less favourable if mammographies are performed outside the context of organised screening programmes. In Switzerland we are now confronted with growing regional disparities in access to screening mammography which is under systematic quality control. CONCLUSIONS: The decrease in breast cancer mortality in Switzerland is most probably due to treatment developments and changes in cause-of-death coding. Public health measures in Switzerland should aim at regulating quality control for screening mammography, monitoring mammography use and improving the information on mammography available to women. For an evidence-based decision regarding health insurance coverage of screening mammography in 2007, large gaps need to be filled. The current coexistence of systematic screening programmes and opportunistic screening, with distinct regional differences, provides a unique opportunity for research into the merits and drawbacks of the two approaches.

Aged↗