1,873 research outputs found
Trace-strength and source-monitoring accounts of accuracy and metacognitive resolution in the misinformation paradigm
No full textTwo experiments are reported that investigate the impact of misinformation on memory accuracy and metacognitive resolution. In Experiment 1, participants viewed a series of photographs depicting a crime scene, were exposed to misinformation that contradicted details in the slides, and later took a recognition memory test. For each answer, participants were required to indicate whether they were willing to testify (report) their answer to the Court and to rate confidence. Misinformation impaired memory accuracy but it had no effect on resolution, regardless of whether resolution was indexed with confidence-rating measures (gamma correlation and mean confidence) or a report-option measure (type-2 discrimination: d’). In Experiment 2, a similar accuracy-confidence dissociation was found, and the misinformation effect occurred mostly with fine-grained responses, suggesting that responding was based on recollected details. We argue that the results support source-monitoring accounts of accuracy and resolution rather than accounts based on trace strength
Measuring manual dexterity and anxiety in divers using a novel task at 35-41 m
No full textBackground: nitrogen narcosis has a detrimental impact on the manual dexterity of divers and prior research has suggested that this impairment may be magnified by anxiety. Preliminary findings of the effects of depth (i.e., narcosis) and subjective anxiety on a novel test of manual dexterity are presented. Methods: there were 45 subjects who were given a test of manual dexterity once in shallow water (1–10 m/3–33 ft) and once in deep water (35–41 m/115–135 ft). Subjective anxiety was concurrently measured in 33 subjects who were split into ‘non-anxious’ and ‘anxious’ groups for each depth condition. Results: subjects took significantly longer (seconds) to complete the manual dexterity task in the deep (mean 5 52.8; SD 5 12.1) water compared to the shallow water (mean 5 46.9; SD 5 8.4). In addition, anxious subjects took significantly longer to complete the task in the deep water (mean 5 48.6; SD 5 6.8) compared to non-anxious subjects (mean 5 53.2; SD 5 9.9), but this was not the case in the shallow water. Discussion: this selective effect of anxiety in deep water was taken as evidence that anxiety may magnify narcotic impairments underwater. It was concluded that the test of manual dexterity was sensitive to the effects of depth and will be a useful tool in future research
Global subjective memorability and the strength-based mirror effect
No full textBetween-list manipulations of memory strength through repetition commonly generate a mirror effect, with more hits, and fewer false alarms for strengthened items. However, this pattern is rarely seen with within-list manipulations of strength. Three experiments investigated the conditions under which a within-list mirror effect of strength (items presented once or thrice) is observed. In Experiments 1 and 2, we indirectly manipulated the overall subjective memorability of the studied lists by varying the proportion of non-words. A within-list mirror effect was observed only in Experiment 2, where a higher proportion of non-words was presented in the study list. In Experiment 3, the presentation duration for each item (0.5 s versus 3 s) was manipulated between groups with the purpose of affecting subjective memorability: A within-list mirror effect was observed only for the short-presentation durations. Thus, across three experiments, we found the within-list mirror effect only under conditions of poor overall subjective memorability. We propose that when the overall subjective memorability is low, people switch their response strategy on an item-by-item basis, and that this generates the observed mirror effect. <br/
Implicit learning of conjunctive rule sets: An alternative to artificial grammars
No full textA single experiment is reported that investigated implicit learning using a conjunctive rule set applied to natural words. Participants memorized a training list consisting of words that were either rare-concrete and common-abstract or common-concrete and rare-abstract. At test, they were told of the rule set, but not told what it was. Instead, they were shown all four word types and asked to classify words as rule-consistent words or not. Participants classified the items above chance, but were unable to verbalize the rules, even when shown a list that included the categories that made up the conjunctive rule and asked to select them. Most participants identified familiarity as the reason for classifying the items as they did. An analysis of the materials demonstrated that conscious micro rules (i.e., chunk knowledge) could not have driven performance. We propose that such materials offer an alternative to artificial grammar for studies of implicit learning
Memory and metacognition in dangerous situations: investigating cognitive impairment from gas narcosis in undersea divers
No full textObjective: The current study tested whether undersea divers are able to accurately judge their level of memory impairment from inert gas narcosis.Background: Inert gas narcosis causes a number of cognitive impairments, including a decrement in memory ability. Undersea divers may be unable to accurately judge their level of impairment, affecting safety and work performance.Method: In two underwater field experiments, performance decrements on tests of memory at 33 to 42 m were compared with self-ratings of impairment and resolution. The effect of depth (shallow [1-11 m] vs. deep [33-42 m]) was measured on free-recall (Experiment 1; n = 41) and cued-recall (Experiment 2; n = 39) performance, a visual-analogue self-assessment rating of narcotic impairment, and the accuracy of judgements-of-learning (JOLs).Results: Both free- and cued-recall were significantly reduced in deep, compared to shallow, conditions. This decrement was accompanied by an increase in self-assessed impairment. In contrast, resolution (based on JOLs) remained unaffected by depth. The dissociation of memory accuracy and resolution, coupled with a shift in a self-assessment of impairment, indicated that divers were able to accurately judge their decrease in memory performance at depth.Conclusion: These findings suggest that impaired self-assessment and resolution may not actually be a symptom of narcosis in the depth range of 33 to 42 m underwater and that the divers in this study were better equipped to manage narcosis than prior literature suggested. The results are discussed in relation to implications for diver safety and work performance
A little bias goes a long way: the effects of feedback on the strategic regulation of accuracy on formula-scored tests
No full textUnder formula-scoring rules for multiple-choice exams, a penalty is applied to incorrect responses to reduce noise in the observed score. To avoid the penalty individuals are allowed to “pass,” and therefore they must be able to strategically regulate the accuracy of their reporting by deciding which and how many questions to answer. To investigate the effect of bias within this framework, Higham (2007) introduced bias profiles, which show the score obtained under formula scoring (corrected score) as a function of the omission rate. Bias profiles estimate the optimal number of questions that should be answered to maximize the corrected score (i.e., optimal bias). Our initial research showed that individuals tend to be too conservative when setting reporting criteria, “omitting” too many answers. The present three experiments introduced a feedback manipulation whereby participants were informed of the optimal omission rate after completing a test and asked to alter their reporting decisions accordingly. This feedback and concomitant alteration of reporting decisions led to improved corrected scores on true/false (Experiment 1), two-alternative tests (Experiments 2), and four-alternative tests (Experiment 3). Importantly, corrected scores at optimal bias also were higher than at forced-report for both true/false and two-alternative tests. Furthermore, in Experiment 3, feedback based on one test improved scores on a second test, and participants were more likely to perform optimally on a third test without feedback. These effects suggest that optimal-bias feedback may have long-term effects and generalize to new tests
Error analysis of QR algorithms for computing Lyapunov exponents
No full textLyapunov exponents give valuable information about long term dynamics. The discrete and continuous QR algorithms are widely used numerical techniques for computing approximate Lyapunov exponents, although they are not yet supported by a general error analysis. Here, a rigorous convergence theory is developed for both the discrete and continuous QR algorithm applied to a constant coefficient linear system with real distinct eigenvalues. For the discrete QR algorithm, the problem essentially reduces to one of linear algebra for which the timestepping and linear algebra errors uncouple and precise convergence rates are obtained. For the continuous QR algorithm, the stability, rather than the local accuracy, of the timestepping algorithm is relevant, and hence the overall convergence rate is independent of the stepsize. In this case it is vital to use a timestepping method that preserves orthogonality in the ODE system. We give numerical results to illustrate the analysis. Further numerical experiments and a heuristic argument suggest that the convergence properties carry through to the case of complex conjugate eigenvalue pairs
The dud-alternative effect in memory for associations: putting confidence into local context
No full textWhen participants are asked to provide confidence judgments for each provided alternative in a multiple-choice memory task, such judgments are inflated if assessed alternatives are accompanied by an implausible (dud) alternative. This finding, termed the dud-alternative effect, has been recently documented in a memory setting with a line-up procedure (Charman, Wells, & Joy, 2011). In the present study we develop a novel paradigm to investigate the dud-alternative effect in memory. The paradigm utilizes a multiple-choice associative recognition task in which dud alternatives can be rejected on the basis of their unfamiliarity. In two experiments we demonstrate a reliable dud-alternative effect with our novel procedure. The results demonstrate that the dud-alternative effect in episodic memory is not limited to tasks based on perceptual factors but is a general phenomenon concerning confidence judgments
Confidence in forced-choice recognition: what underlies the ratings?
No full textTwo-alternative forced-choice recognition tests are commonly used to assess recognition accuracy that is uncontaminated by changes in bias. In such tests, participants are asked to endorse the studied item out of two presented alternatives. Participants may be further asked to provide confidence judgements for their recognition decisions. It is often assumed that both recognition decisions and confidence judgements in two-alternative forced-choice recognition tests depend on participants' assessments of a difference in strength of memory evidence supporting the two alternatives - the relative account. In the present study we focus on the basis of confidence judgments and we assess the relative account of confidence against the absolute account of confidence, by which in assigning confidence participants consider only strength of memory evidence supporting the chosen alternative. The results of the study show that confidence in two-alternative forced-choice recognition decisions is higher when memory evidence is stronger for the chosen alternative and also when memory evidence is stronger for the unchosen alternative. These patterns of results are consistent with the absolute account of confidence in two-alternative forced-choice recognition but they are inconsistent with the relative account
Analysis of the singular value decomposition as a tool for processing microarray expression data
No full textWe give two informative derivations of a spectral algorithm for clustering and partitioning a bi-partite graph. In the first case we begin with a discrete optimization problem that relaxes into a tractable continuous analogue. In the second case we use the power method to derive an iterative interpretation of the algorithm. Both versions reveal a natural approach for re-scaling the edge weights and help to explain the performance of the algorithm in the presence of outliers. Our motivation for this work is in the analysis of microarray data from bioinformatics, and we give some numerical results for a publicly available acute leukemia data set
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