Worth a quick look? Initial scene previews can guide eye movements as a function of domain-specific expertise but can also have unforeseen costs

Rapid scene recognition is a global visual process we can all exploit to guide search. This ability is thought to underpin expertise in medical image perception yet there is no direct evidence that isolates the expertise-specific contribution of processing scene previews on subsequent eye movement performance. We used the flash-preview moving window paradigm (Castelhano & Henderson, 2007) to investigate this issue. Expert radiologists and novice observers underwent 2 experiments whereby participants either saw a 250ms scene preview or a mask before searching for a target. Observers looked for everyday objects from real-world scenes (Experiment 1), and searched for lung nodules from medical images (Experiment 2). Both expertise groups exploited the brief preview of the upcoming scene to more efficiently guide windowed search in Experiment 1, but there was only a weak effect of domain-specific expertise in Experiment 2, with experts showing small improvements in search metrics with scene previews. Expert diagnostic performance was better than novices in all conditions but was not contingent on seeing the scene preview, and scene preview actually impaired novice diagnostic performance. Experiment 3 required novice and experienced observers to search for a variety abnormalities from different medical images. Rather than maximising the expertise-specific advantage of processing scene previews, both novices and experienced radiographers were worse at detecting abnormalities with scene previews. We discuss how restricting access to the initial glimpse can be compensated for by subsequent search and discovery processing, but there can still be costs in integrating a fleeting glimpse of a medical scene

Looking for cancer: Expertise related differences in searching and decision making

We examined how the ability to detect lung nodules in chest x-ray inspection is reflected in experience-related differences in visual search and decision making, and whether the eye-tracking metric time-to-first hit showed systematic decreases across expertise levels are examined. In the study decision making improved with expertise, however, time-to-first fixate a nodule showed only a non-significant trend to decrease with expertise. Surprisingly, naïve and expert observers allocated less visual attention at nodules compared with first and third year radiography students. This similarity in visual attention at nodules but not in decision making was explained by the fact that naïve observers were more likely to fixate and make errors on distracter regions. Time-to-first hit has been linked to expert performance in mammography, but in this study was not sufficiently sensitive to demonstrate clear linear improvements across expertise groups. This brings into question the use of this metric as an indirect measure of rapid initial holistic processing

The flash-preview moving window paradigm: Unpacking visual expertise one glimpse at a time

How we make sense of what we see and where best to look is shaped by our experience, our current task goals and how we first perceive our environment. An established way of demonstrating these factors work together is to study how eye movement patterns change as a function of expertise and to observe how experts can solve complex tasks after only very brief glances at a domain-specific image. The primary focus of this paper is to introduce an innovative gaze-contingent method called the ‘Flash-Preview Moving Window’ (FPMW) paradigm (Castelhano & Henderson, 2007), which was recently developed to understand our shared expertise in scene perception and how our first glimpse of a scene is used to guide our eye movement behaviour. In keeping with this special issue on visual expertise and medicine, this paper will highlight how the FPMW paradigm has the potential to resolve long-standing theoretical issues as to how, right from the very first glance, experts are able to process domain-specific images and guide their eye movements better than novices. Since FPMW is a gaze-contingent eye-tracking method, the paper will first outline the current methodological and theoretical frontier, and how the FPMW paradigm bridges established methods used to investigate visual expertise. The paper will discuss a recent example in which the FPMW was employed to investigate medical image perception expertise for the first time (Litchfield & Donovan, 2016), and by discussing the insights and challenges this method offers, this should ultimately deepen our understanding of visual expertise

Investigating the effects of mopane worms (Imbrasia belina) on nutrients, Venetia-Limpopo Nature Reserve, South Africa

Ecologists have long been aware that large mammalian herbivores can alter ecosystem functioning in various ways, for example through changing where they defecate and urinate, which consequently affects nutrient cycling. The effects of herbivorous insects on ecosystems, however, have received limited attention until recently. Insects are capable of mass outbreaks, they can consume large volumes of vegetative material and can deposit large quantities of dung (frass), one example being the mopane worm, Imbrasia belina. This study looked at the effect of mopane worm frass on soil fertility in the mopane veld of the Venetia-Limpopo Nature Reserve and neighbouring Haakdoring farm. It found that mopane worms are capable of altering soil nutrient dynamics beneath the trees where they are browsing in three ways. Firstly, they increase the potential amount of nutrients deposited when compared with that deposited through conventional leaf litter. Secondly, they alter the rate of nutrient recycling by depositing nutrients in frass which decomposes more rapidly than conventional leaf litter. Lastly, they increase the amounts of potassium and phosphorus in the soil. While there is no conclusive data from this study that the mopane veld would become extinct if mopane worms were harvested to extinction, it has shown that there is relatively little evidence on how herbivorous insects could affect ecosystem functioning in the landscapes in which they occur. Further research is recommended that investigates how mopane worms influence soil fertility in more detail and over multiple geographical locations

Detection or decision errors? Missed lung cancer from the posteroanterior chest radiograph

A test bank of verified chest radiographs was compiled for visual search experiments to investigate radiology performance in the detection of early lung cancer. A measure of the physical characteristics of the lesions was derived to determine the conspicuity (x) of the nodules and to investigate possible causes of failed detection. Observer performance was measured by alternate free response operating characteristic (AFROC) methodology and was supplemented with visual search recording. Correlation of AFROC scores and the x values was poor but inspection of the visual search recordings showed that most nodules were fixated. Fixations on missed lesions produced average dwell times greater than three times the minimum duration thought to be associated with detection. We conclude that the majority of errors were failures of decision rather than detection and comment on the implications of this for strategies to improve diagnostic effectiveness

False memory guided eye movements::insights from a DRM-Saccade paradigm

The Deese-Roediger and McDermott (DRM) paradigm and visually guided saccade tasks are both prominent research tools in their own right. This study introduces a novel DRM-Saccade paradigm, merging both methodologies. We used rule-based saccadic eye movements whereby participants were presented with items at test and were asked to make a saccade to the left or right of the item to denote a recognition or non-recognition decision. We measured old/new recognition decisions and saccadic latencies. Experiment 1 used a pro/anti saccade task to a single target. We found slower saccadic latencies for correct rejection of critical lures, but no latency difference between correct recognition of studied items and false recognition of critical lures. Experiment 2 used a two-target saccade task and also measured corrective saccades. Findings corroborated those from Experiment 1. Participants adjusted their initial decisions to increase accurate recognition of studied items and rejection of unrelated lures but there were no such corrections for critical lures. We argue that rapid saccades indicate cognitive processing driven by familiarity thresholds. These occur before slower source-monitoring is able to process any conflict. The DRM-saccade task could effectively track real-time cognitive resource use during recognition decisions

Current trends in lower limb Doppler scanning in Ireland

Introduction: The clinical need to diagnose and treat above knee deep vein thrombosis (AKDVT) has long been established in literature and in practice. On the other hand, the need to diagnose and treat below knee deep vein thrombosis (BKDVT) continues to be debated in literature. This has resulted in variation in clinical guidelines and protocols nationwide. This research aims to establish if there is a standard practice in Irish ultrasound departments and if so, what that practice is and where sonographers are getting information to inform this. Methods: A questionnaire was designed using SurveyMonkey and distributed using online platforms. The questionnaire aimed to establish the experience of the sonographer, the types of exams performed, protocols/guidelines used as well as scenarios where the sonographer might deviate from protocol. Results: The study yielded 90 responses. The research found 49% of sites perform whole leg ultrasound routinely and 46% perform proximal ultrasound only. 41% of respondents said their protocols were based on clinical guidelines however, 22% of participants didn't know what these guidelines were. 49% of respondents were unaware of what treatment a patient would receive in cases where there is a high clinical suspicion of DVT, but the ultrasound is negative for DVT. Conclusion: The research has established a lack of consistency amongst sonographers and scanning practices with a fairly even split (49% of respondents perform whole leg ultrasound and 46% perform proximal only). Not only has the research identified a lack of standardised scanning approach nationwide, but inconsistencies are also seen in the guidelines that inform our department's protocols as well as inconspicuous terms used in radiology reporting and jargon in literature in relation to DVT. Implications for practice: 1. An inconsistency in practice has been established. Discussions are now needed to decide what guidelines should be implemented into Irish Ultrasound DVT protocols. 2. A national protocol for BKDVT would result in all patients in Ireland having access to the same standard of care. 3. Call for consensus on appropriate training for sonographers undertaking LLDs

An investigation of the effects of age and stroke on implicit motor imagery as demonstrated by a hand laterality judgment test

Background Explicit motor imagery is recommended for stroke rehabilitation but can be difficult to practice. Hand Laterality Judgement (HLJ) stimulates implicit motor imagery which may be easier for stroke patients, but its benefits are unknown. Previous studies are inconclusive and have not considered the effects of older age. Objectives. This thesis investigated the effects of older age and stroke on HLJ and the effects of practising HLJ after a stroke. Methods Three experiments were undertaken. The first compared HLJ in twenty young, healthy participants (mean=22(2) years) with twenty aged 60 -70 years (mean=67(3) years) and twenty-two aged ≥ 70 years (mean=77(5) years). The second compared HLJ of eleven stroke survivors aged ≥ 60 years (mean =69 (6)) with age-matched controls. The third examined the effects of practising HLJ in four stroke survivors. Main findings There were no significant differences in HLJ response times between the young and older groups (p=.06) or between the stroke and control group (p=.13). Both older groups were significantly less accurate than the younger group (young group =92%; older groups= 81%-86% p≤ .00). There were no significant differences in accuracy between the two older groups (P=.10) or between the stroke and control groups (p=.59). All groups engaged in implicit motor imagery, but this was impaired by early old age. Visuospatial imagery was impaired in later old age and by stroke. There were no significant relationships between HLJ performance and upper limb impairment post-stroke. There were no significant effects of practising HLJ, but trends towards increased accuracy (d=.24) and slower response times (d=.46). Conclusion. Stroke survivors can perform HLJ as well as similarly aged healthy individuals. Stroke may impair visuospatial imagery, but accuracy improves with practice. Further research is needed to determine if there are any benefits to post-stroke upper limb rehabilitation