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Biomedical subjects

N Donnelly

Publications and source records attributed to N Donnelly.

7 recordsLinked to original sources
PubMed1992

Parallel pattern processing and visual agnosia.

A series of visual search experiments are reported examining pattern processing in a visual agnosic patient. We examined search for targets defined by: (I) the combination of their features relative to homogeneous distractors; (2) the combination of their features relative to heterogeneous distractors; and (3) a single feature difference relative to the distractors (their orientation). Normal subjects demonstrate evidence of spatially parallel search when combined-feature targets are detected against homogeneous distractors, and when targets are defined by a salient feature difference. There are non-linear effects of the number of distractors present, and absent responses can be as fast as present. In contrast, search times for combined-feature targets amongst heterogeneous distractors increase linearly with display size, with the slope for absent responses about twice that for present. The contrast between search for combined-feature targets amongst homogeneous and heterogeneous distractors can be attributed to the effects of grouping between distractors and between distractors and targets (Duncan & Humphreys, 1989, 1992; Humphreys & Muller, in press). Grouping between homogeneous distractors facilitates search. An agnosic patient, HJA, showed normal search functions for single-feature targets and for combined-feature targets amongst heterogeneous distractors. However, he was impaired at search for combined-feature targets amongst homogeneous distractors. This suggests that HJA is selectively impaired at grouping conjunctions of form features. The relations between HJA's agnosia and his problem in the parallel grouping of form conjunctions are discussed, as are the implications of the work for understanding normal vision.

Adult↗
PubMed1992

Prevalences and perceptions of licit and illicit drugs among New South Wales secondary school students, 1989.

This paper presents findings on drug prevalences for licit and illicit drugs among New South Wales secondary school students (n = 3753) in late 1989. It also considers the accuracy of students' perceptions of the drug causing the most and fewest drug-related deaths. Data were analysed by age and gender, using logistic regression for the prevalence data. Findings indicate that licit drugs (tobacco, alcohol and analgesics) were the most frequently and widely used. Rates for illicit drugs were low, although there was some degree of experimental use of cannabis which increased amongst older males. Perceptions were found to be inaccurate in emphasising the dangers of the illicit drug heroin over those of the licit drugs tobacco and alcohol. Reasons for these findings are discussed, and more in-depth research recommended into the relationship between drug prevalences and perceptions for different age groups, and its relevance for planning drug prevention initiatives.

Adolescent↗
PubMed1992

Changes in reported drug prevalence among New South Wales secondary school students, 1983 to 1989.

Three drug use surveys employing a standardised questionnaire format and sampling procedure were conducted on samples of New South Wales school students in 1983, 1986 and 1989. Alcohol and tobacco were the most frequently used substances across the surveys, with rates of use of illicit substances being considerably lower. Declines in the prevalence of alcohol, tobacco and stimulant use were found between 1983 and 1986 and between 1986 and 1989 for both males and females. Rates of use of inhalants, sedatives, hallucinogens and narcotics declined between 1983 and 1986, but remained unchanged between the 1986 and 1989 samples. Cannabis use declined significantly among females between 1983 and 1989, but not among males. Possible reasons for the general decline in drug use over the six-year period are discussed.

Adolescent↗
PubMed1991

Parallel computation of primitive shape descriptions.

This article reports evidence that parallel search functions can occur when heterogeneous conjunction elements configure into a single object description. Experiment 1 demonstrates parallel search for form conjunctions presented in displays of heterogeneous nontargets when closure and good continuation between display elements are exhibited. When closure and good continuation are absent, reaction times increase linearly with set size (Experiment 2). Experiment 3 demonstrates a halfway stage between these two extremes, in which displays have closure but not good continuation. Finally, selection of object descriptions is shown to be temporally limited to one object at a time (Experiment 4). The data are incompatible with both local feature-based and distractor similarity-based accounts of visual search; however, they are compatible with there being an important role for preattentive feature combinations forming primitive object descriptions. Parallel search functions can occur when heterogeneous conjunctions configure into a single object description.

Adult↗
PubMed1990

Object superiority: a comparison of complete and part probes.

Previous research on object superiority effects has shown that certain contexts enhance the recognition of an object part. However, those contexts would not normally be called objects. The present study discusses object superiority within more general issues of object recognition. By using what we call 'complete' probes, superiority effects were extended to exposure durations much longer than those used in previous research. Experiments 1 and 2 found that complete probes gave stable superiorities at 250 msec and even 2-sec stimulus exposures. These object superiority effects were found for both objects (faces and chairs) investigated. Experiment 3 showed that object superiorities established with complete probes were not necessarily greater than those for part probes. The experiments stress the role of spatial arrangement of object parts in accessing stored information. It is argued that a successful match of a structural description to a representation in long-term memory influences stimulus processing by allowing the formation of higher level features.

Adult↗