ORCID Profile
0000-0001-8769-1331
Current Organisation
Deakin University
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Publisher: Elsevier BV
Date: 05-2023
Publisher: SAGE Publications
Date: 2011
DOI: 10.1068/P6892
Abstract: Failure to detect change under circumstances where visual input is interrupted or attention is distracted is indicative of the capacity limits of visual short-term memory. The current study attempts to probe the nature of these limits. In experiment 1, the appearance of single Gabor patches was altered across colour, size, or speed, and set size was manipulated by means of a visual cue. In experiment 2, performance for detecting single and multiple changes to Gabor patches was compared under the constraint that the inherent detectability of each in idual change was the same. Experiment 1 yielded a particular set size (4) and a particular level of change magnitude at which performance was equivalent across change type. On the basis of these parameter values, experiment 2 revealed that the detectability of two features changing within one object was the same as the detectability of a single feature changing across two objects, and that this level of detectability could be predicted by a simple model of probability summation. Together, these results suggest that performance is determined by the magnitude of featural changes independently of the way they are distributed across objects. We suggest they are adequately explained by a flexible-resource-allocation model rather than a slot-allocation model.
Publisher: Wiley
Date: 06-06-2021
DOI: 10.1111/PSYP.13871
Abstract: Attentional lapses interfere with goal‐directed behaviors, which may result in harmless (e.g., not hearing instructions) or severe (e.g., fatal car accident) consequences. Task‐related functional MRI (fMRI) studies have shown a link between attentional lapses and activity in the frontoparietal network. Activity in this network is likely to be mediated by the organization of the white matter fiber pathways that connect the regions implicated in the network, such as the superior longitudinal fasciculus I (SLF‐I). In the present study, we investigate the relationship between susceptibility to attentional lapses and relevant white matter pathways in 36 healthy adults (23 females, M age = 31.56 years). Participants underwent a diffusion MRI (dMRI) scan and completed the global–local task to measure attentional lapses, similar to previous fMRI studies. Applying the fixel‐based analysis framework for fiber‐ specific analysis of dMRI data, we investigated the association between attentional lapses and variability in microstructural fiber density (FD) and macrostructural (morphological) fiber‐bundle cross section (FC) in the SLF‐I. Our results revealed a significant negative association between higher total number of attentional lapses and lower FD in the left SLF‐I. This finding indicates that the variation in the microstructure of a key frontoparietal white matter tract is associated with attentional lapses and may provide a trait‐like biomarker in the general population. However, SLF‐I microstructure alone does not explain propensity for attentional lapses, as other factors such as sleep deprivation or underlying psychological conditions (e.g., sleep disorders) may also lead to higher susceptibility in both healthy people and those with neurological disorders.
Publisher: SAGE Publications
Date: 2011
DOI: 10.1068/P6890
Abstract: Change blindness refers to the difficulty observers have in detecting otherwise obvious changes to visual stimuli, when these changes are masked in some way. Typically, change blindness is studied by using complex visual scenes and complex changes to these scenes. In the current study, we used a more controlled visual environment, presenting observers with a series of oriented, sinusoidal patterns (Gabors), one of which underwent a change during a blanking of the screen. Changes were made to different features (size, colour, spatial frequency, and speed) with the target – distractor discriminability varying. The detectability of these changes was quantified by calculating psychometric functions and thresholds for each in idual observer. Thresholds for the detection of changing features were higher than those for non-changing features, but thresholds for both tasks show consistency across observers. Psychometric-function slopes show consistency across observers and change type only for non-changing targets. For changing targets, psychometric-function slopes show no obvious pattern across observers or change types. We suggest this reflects vSTM treating different features as abstract, interchangeable tokens, as alternative explanations (such as additional noise in vSTM) can be ruled out.
Publisher: SAGE Publications
Date: 2010
DOI: 10.1068/P6529
Abstract: Observers typically report illusory colour on achromatic gratings after being adapted to orthogonally oriented gratings presented in complementary colours, where the colour apparent on each grating is complementary to the one that had been presented with that grating during adaptation (McCollough, 1965 Science149 1115–1116). We used this procedure, but presented homogenous fields at test instead of achromatic gratings. When adaptation stimuli moved in directions locally orthogonal to their orientation, we found that, for up to 7–8 min after adaptation, a flower-like illusory pattern was evident on both homogenous fields after this time illusory radial lines and concentric circles were evident and were colour-contingent (eg for adaptation with green concentric circles and magenta radial lines, concentric circles were apparent on a magenta test field and radial lines were apparent on a green test field). When stimuli were stationary during induction, colour-contingent illusory forms were also apparent at test. The results demonstrate that an aftereffect, reciprocal to the McCollough effect, can be produced under appropriate induction conditions, and that this effect is not due to retinal afterimages.
Publisher: SAGE Publications
Date: 2012
DOI: 10.1068/P7176
Abstract: Change blindness is the failure of observers to notice otherwise obvious changes to a visual scene when those changes are masked in some way (eg by blotches or a blanking of the screen). Typically, change blindness is taken as evidence that our representation of the visual world is capacity limited. The locus of this capacity limit is thought to be visual short-term memory (vSTM). The capacity of vSTM is usually estimated with a high-threshold model which assumes that each element in the stimulus array is either fully encoded or not encoded at all, and, furthermore, that false alarms can arise only by guessing, not by noise. Low-threshold models, by contrast, suggest that false alarms can arise by noise at the level of detection/discrimination and/or decision. In this study, we use a well-controlled stimulus display in which a single element changes over a blanking of the screen and contrast predictions from a popular high-threshold model of vSTM with the predictions of a low-threshold model (specifically, the s le-size model) of visual search and vSTM. The data were better predicted by the low-threshold model.
Publisher: Springer Science and Business Media LLC
Date: 11-03-2021
Publisher: Center for Open Science
Date: 26-05-2020
Abstract: A common problem in vision research is explaining how humans perceive a coherent, detailed and stable world despite the fact that the eyes make constant,jumpy movements and the fact that only a small part of the visual field can beresolved in detail at any one time. This is essentially a problem of integrationover time - how successive views of the visual world can be used to create theimpression of a continuous and stable environment. A common way of studyingthis problem is to use complete visual scenes as stimuli and present a changedscene after a disruption such as an eye movement or a blank screen. It is found inthese studies that observers have great difficulty detecting changes made duringa disruption, even though these changes are immediately and easily detectablewhen the disruption is removed. These results have highlighted the importance ofmotion cues in tracking changes to the environment, but also reveal the limitednature of the internal representation. Change blindness studies are interestingas demonstrations but can be difficult to interpret as they are usually applied tocomplex, naturalistic scenes. More traditional studies of scene analysis, such asvisual search, are more abstract in their formulation, but offer more controlledstimulus conditions. In a typical visual search task, observers are presented withan array of objects against a uniform background and are required to report onthe presence or absence of a target object that is differentiable from the otherobjects in some way. More recently, scene analysis has been investigated bycombining change blindness and visual search in the ‘visual search for change’paradigm, in which observers must search for a target object defined by a changeover two presentations of the set of objects. The experiments of this thesis investigate change blindness using the visual search for change paradigm, but alsouse principles of design from psychophysical experiments, dealing with detectionand discrimination of basic visual qualities such as colour, speed, size, orientationand spatial frequency. This allows the experiments to precisely examine the roleof these different features in the change blindness process. More specifically, theexperiments are designed to look at the capacity of visual short-term memory fordifferent visual features, by examining the retention of this information acrossthe temporal gaps in the change blindness experiments. The nature and fidelityof representations in visual short-term memory is also investigated by manipulating (i) the manner in which featural information is distributed across space andobjects, (ii) the time for which the information is available, (iii) the manner inwhich observers must respond to that information. Results point to a model inwhich humans analyse objects in a scene at the level of features/attributes ratherthan at a pictorial/object level. Results also point to the fact that the working representations which humans retain during visual exploration are similarlyfeature- rather than object-based. In conclusion the thesis proposes a model ofscene analysis in which attention and vSTM capacity limits are used to explainthe results from a more information theoretic standpoint.
No related grants have been discovered for Alex Burmester.