Search PubMed⌕ Search

Biomedical subjects

L M Ward

Publications and source records attributed to L M Ward.

At least 55 records · Page 3Linked to original sources
PubMed1987

Remembrance of sounds past: memory and psychophysical scaling.

What is the role of long-term memories of previous stimulus-response mappings, and of previous sensory and perceptual experiences generally, in psychophysical scaling judgments? I conducted four experiments in an attempt to provide some preliminary answers to this question. In each experiment, subjects made judgments of the loudness of sounds on 3 successive days. Stimulus intensities were drawn randomly from the same set on Days 1 and 3 but from a different set, either all 12 dB higher or all 12 dB lower, on Day 2. Four different types of psychophysical scaling judgments were studied: category judgment without an experimenter-induced identification function, ratio magnitude estimation with a variable standard, absolute magnitude estimation, and cross-modality matching. The first two methods required completely relative judgment, the last two completely absolute judgment. Data from all methods reveal profound effects of stimulus-response mappings experienced on previous days (long-term memory) and immediately previous stimuli and responses (short-term memory) on responses to current stimuli. Responses were typically a compromise between absolute and relative judgment. Individual differences were dramatic.

Female↗
PubMed1987

Antiphospholipid antibodies associated with retinal vascular disease.

Two patients with retinal vascular disease also had antiphospholipid antibodies, defined by the presence of the circulating lupus anticoagulant (LAC), anticardiolipin antibodies, or both. One had retinal arterial occlusions and the other had a nonischemic central retinal vein occlusion. The association of thrombotic vascular disease, including both retinal and cerebral vessels, with the presence of these antibodies should be investigated in otherwise normal individuals or in patients presenting with a lupuslike syndrome and retinal vascular occlusive disease. Low-dose aspirin administration could be of therapeutic value in managing thrombotic events in this group of patients.

Adult↗
PubMed1986

The relationship between articulation disorders and motor coordination in children.

This study was designed to examine the relationship between articulation disorders, soft neurological signs, and motor abilities. Fifteen children with articulation problems, as measured by the Templin-Darley Articulation Screening Test and a connected speech sample, were compared with a normal control group (matched for sex and age) on the Quick Neurological Screening Test, the Imitation of Postures test (from the Southern California Sensory Integration Tests), and the 1984 version of the Stott Test of Motor Impairment that has been revised by Henderson. A significant difference was found between the groups on the Motor Impairment Test and the Quick Neurological Screening Test, supporting the hypothesis that the articulation disorder children would have more motor coordination problems and soft neurological signs than the normal children in the control group. There was no between-group difference on the Imitation of Postures test, suggesting that as a group, children with articulation deficits are not dyspraxic. This study supports other research findings stating a relationship between articulation problems and motor impairment, but it also indicates that this motor impairment is not necessarily dyspraxia.

Articulation Disorders↗
PubMed1982

Determinants of attention to local and global features of visual forms.

This article deals with the problem of how attention is distributed to different levels of detail (global, local) in visual scenes. Six experiments explore the effect of a previous level of processing on current processing. The contention that processing at a given level of detail biases the distribution of attention so that more is allocated to that level for future processing is supported by the presence in the data of a robust level-readiness effect, whereby processing is faster at a given level if previous processing has been at that level. The level-readiness effect occurs regardless of the conspicuity of features at the various levels. Conflict between levels seems to depend on the imbalance of conspicuity and attention allocation between levels, with the more conspicuous or attended-to-level interfering more. A model of two-state attention switching similar to that of Sperling and Melchnor (1978) is proposed to explain these data. the final experiment confirmed the somewhat unusual prediction of this model that sometimes processing under focusing-attention conditions can be slower than that under divided-attention conditions.

Attention↗
PubMed1979

Levels of processing in visual illusions: the combination and interaction of distortion-producing mechanisms.

In order to assess the mode and sequence of interaction of visual-geometric illusion mechanisms, responses to simple and composite overestimation configurations were measured in 72 observers. Analysis suggests that some illusion mechanisms add their distortions to the outputs of others and that other mechanisms average. A logarithmic or near-logarithmic transformation seems to occur when illusory effects combine. A path analysis of the results suggests that some illusory mechanisms combine in a serial manner and that others operate on separate parallel channels. Notions based on simple addition of illusory effects and on serial linear processing are not supported by these analyses.

Discrimination Learning↗
PubMed1979

Stimulus information and sequential dependencies in magnitude estimation and cross-modality matching.

Descriptive models of magnitude estimation and cross-modality matching derived from two different approaches to psychophysical judgment, the response ratio hypothesis and the fuzzy judgment approach, are compared. The two approaches emphasize different bodies of facts but both attempt to account for sequential dependencies in psychophysical judgments. Both models suggest a hierarchical multiple linear regression model for such data. Some of the predictions of the models are explored in the context of two experiments in which the amount of stimulus information available to subjects in magnitude estimation and cross-modality matching tasks is varied. The fuzzy judgment approach generally does better in explaining the form of such data.

Adolescent↗
PubMed1977

The case for misapplied constancy scaling: depth associations elicited by illusion configurations.

It has been suggested that many visual-geometric illusions arise from inappropriate evocation of size-constancy by depth cues implicit in illusion configurations. Observers gave free association responses while viewing illusion figures. Analysis of these responses provides weak but consistent evidence for the elicitation of depth in the Sander parallelogram, Mueller-Lyer, Zoellner, and Ehrenfels variant of the Ponzo illusion. No evidence for depth is found in the normal form of the Ponzo, Poggendorff, and horizontal-vertical illusions, and the evidence is ambiguous in the Orbison configurations. These results indicate that depth processing may be evoked by some, but not all, classical illusion forms.

Cues↗
PubMed1976

Levels of feature analysis in processing visual patterns.

In this paper, a revised Pandemonium-like model of visual-feature processing is formulated and a preliminary test of its feasibility is reported. The model differentiates visual-feature processing into a series of hierarchical stages organized by increasing complexity, with the output of each stage going both to the next higher stage, and directly to a more central processor. In the experiment, subjects sorted decks of cards into piles according to the presence or absence of a target stimulus which differed from nontargets in a variety of different features; detection of a feature was sufficient for detection of a target. The data generally supported the revised Pandemonium model, in that targets which differed from nontargets in features thought to be low in the hierarchy were processed faster than targets whose difference was in a high level feature. An extension of the revised model did somewhat less well in predicting the results of sorting for targets in which detection of any one of several features was sufficient for target detection.

Adult↗