Omission Error Rates Research Articles

Validation of active fire detection from moderate-resolution satellite sensors: the MODIS example in northern eurasia

This paper discusses the process of validating active yes/no binary detection products from moderate-resolution satellite sensors. General concepts and practical issues are illustrated by the validation of the Moderate Resolution Imaging Spectroradiometer (MODIS) active product in Siberia. Coincident Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery is used to characterize spatial patterns of flaming at sub-MODIS pixel scale. It is shown that for proper evaluation reference observations are needed at the scale of the satellite pixel, as only 60% of the MODIS footprints contain single contiguous clusters of ASTER pixels. In Siberia the size of a single ASTER cluster within the MODIS footprint that has a 50% probability of being flagged as fire is ~60, compared to ~45 in the Brazilian Amazon, whereas previous radiative transfer simulations suggested similar detection probabilities. The lower-than-expected detection rates in Siberia are largely attributable to flaming underneath heavy smoke, which is not detected by the current MODIS algorithm. Pixel-based and cluster-based omission error rates are derived, and it is shown that the probability of flagging as fire a MODIS pixel which contains a given number of 30-m ASTER pixels is typically 3-5 times lower than detecting a contiguous cluster with the same number of ASTER pixels. The procedures described are recommended for a consensus active validation protocol, but with the inclusion of multiplatform sensor configurations to complement the near-nadir angular sampling from single-platform observations such as MODIS and ASTER on Terra

A comparison of model selection indices for nested latent class models

Latent Class analysis has been used to study the hierarchical relationship among sets of categorical variables. Researchers routinely use chi-squared statistics as model-selection criteria. Due to the limitation of chi-squared statistics, it is desirable to develop other model selection indices. In this study, we compared the performance of chi-squared statistics with three information criteria, Akaike's AIC, Schwarz's BIC and Bozdogan's CAIC. The factors actually manipulated in this study were types of latent class model and conditional response probabilities including intrusion and omission error rates for certain models. In terms of the performance of the six models, BIC and CAIC were most accurate for the Independence, Proctor and Goodman models, AIC was most accurate for the Extended Intrusion-Omission Error model, while chi-squared difference statistics showed their best performance in some settings of the Extended Proctor model. As for the Intrusion-Omission Error model and some situations in the Extend Proctor model, the performance of the five indices depended on sample sizes and error rates. AIC was preferred in Intrusion-Omission Error model when sample size was small and BIC and CAIC were preferred when sample size was medium. In Proctor model, AIC was more accurate than chi-squared difference statistics when error rate was small. A similar effect occurred in Hierarchy I in Extended Proctor model. With a small error rate, AIC was superior to chi-squared difference statistics but worse with a large error rate. None of the five criteria performed well in Extended Proctor and Extended Intrusion-Omission Error models. In conclusion, the information criteria had superior performance than both chi-squared statistics. Among the information criteria, BIC and CAIC were more appropriate than AIC for the Independence and Proctor models while AIC was more accurate for Extended Proctor model.

Interactions of task and subject variables among continuous performance tests

Contemporary models of working memory suggest that target paradigm (TP) and target density (TD) should interact as influences on error rates derived from continuous performance tests (CPTs). The present study evaluated this hypothesis empirically in a typically developing, ethnically diverse sample of children. The extent to which scores based on different combinations of these task parameters showed different patterns of relationship to age, intelligence, and gender was also assessed. Four continuous performance tests were derived by combining two target paradigms (AX and repeated letter target stimuli) with two levels of target density (8.3% and 33%). Variations in mean omission (OE) and commission (CE) error rates were examined within and across combinations of TP and TD. In addition, a nested series of structural equation models was utilized to examine patterns of relationship among error rates, age, intelligence, and gender. Target paradigm and target density interacted as influences on error rates. Increasing density resulted in higher OE and CE rates for the AX paradigm. In contrast, the high density condition yielded a decline in OE rates accompanied by a small increase in CEs using the repeated letter CPT. Target paradigms were also distinguishable on the basis of age when using OEs as the performance measure, whereas combinations of age and intelligence distinguished between density levels but not target paradigms using CEs as the dependent measure. Different combinations of target paradigm and target density appear to yield scores that are conceptually and psychometrically distinguishable. Consequently, developmentally appropriate interpretation of error rates across tasks may require (a) careful analysis of working memory and attentional resources required for successful performance, and (b) normative data bases that are differently stratified with respect to combinations of age and intelligence.

Evidence for unaltered brain electrical topography during prefrontal response control in cycloid psychoses

Objective Prefrontal structures such as the anterior cingulate cortex (ACC) play a decisive role in processes of action monitoring and response control, functions often impaired in schizophrenia. Patients with cycloid psychoses exhibit some characteristic neurophysiological features not indicative of the cerebral hypofrontality observed in schizophrenia. This study aimed at examining if cycloid psychoses—unlike schizophrenias—involve a normal brain-electrical topography during a task demanding prefrontal response control. Methods Thirty-seven patients with cycloid psychoses and 37 healthy controls were investigated electrophysiologically while performing a Continuous Performance Test (CPT). Topographical analyses were conducted to individually quantify the Nogo-anteriorisation (NGA) as a neurophysiological index of prefrontal response control. Results The patients exhibited an unaltered topography with a mean NGA not significantly different from the controls. They did, however, differ from the control group regarding their Global Field Power (GFP), with a significantly reduced GFP ( p<0.001) and decreased latencies ( p<0.01) during Nogo trials. On a behavioral level, patients exhibited prolonged reaction times and an increased rate of omission errors. Conclusions The investigated patients showed an activation of specific (presumably frontal) brain areas during Nogo trials, resulting in a frontalisation of the brain-electrical field comparable to the control group. However, the strength of this activation was apparently reduced. The patients' unaltered topographical pattern contrasts with previous findings in schizophrenic patients and supports the hypothesis that cycloid psychoses entail less severe prefrontal deficits than schizophrenias, which might be an indication of different biological backgrounds for both groups of endogenous psychoses.

Event-related potentials for response inhibition in Parkinson's disease

This study investigated inhibitory function in patients with Parkinson's disease (PD) by recording event-related brain potentials (ERPs) during a Go/NoGo task. Fourteen healthy volunteers and 13 patients with PD without dementia performed a cued continuous performance test that included Go and NoGo trials. The peak latency, amplitude, and topographic distributions of the ERPs to Go and NoGo stimuli were analyzed. Cognitive function was evaluated using the Wisconsin Card Sorting Test (WCST), Kana Pick-out Test, and Verbal Fluency Test (VFT). Performances in the WCST and VFT were significantly impaired in the PD group as compared with the control group. The PD group had significantly higher rates of omission and commission errors during the ERP task. The ERP study found no differences in the latency and amplitude of the Go-P3 between the two groups. By contrast, the NoGo-P3 latency was significantly longer in the PD group than in the control group. The amplitudes of the NoGo-P3 and NoGo-N2 were also significantly smaller in the PD group than in the control group. The NoGo-P3 latency was significantly correlated with the Kana Pick-out Test and VFT scores. The NoGo-P3 amplitude was significantly correlated with the WCST and VFT scores, as well as with the number of commission errors. There were no significant correlations between the cognitive function tests and either the Go-P3 or NoGo-N2 measures. The behavioral and ERP data suggest that there is selective impairment of inhibitory function in PD and that this deficit may be related to impaired inhibitory executive function in the frontal lobe.

Age and task parameters in continuous performance tests for preschoolers.

66 children (M=56.2 mo., SD=10.9), recruited from preschool and daycare centers, were administered two continuous performance tests, one auditory and one visual. Both tests utilized a format with one target and one nontarget. Interstimulus interval was fixed at 1350 msec. for the visual test and 5000 msec. for the auditory test. The visual test produced greater rates of omission and commission errors than the auditory test. Age was significantly related to mean reaction time and response variability for both tests; however, the visual test produced an unexpected pattern of increasing response time across age groups. On both tests omission rates improved significantly with age, while commission rates were consistent across ages 3-6 years. When considering continuous performance test paradigms for preschoolers, 3-yr.-olds may need at least a 4000-msec. interstimulus interval to make a choice for the stimulus cue. Hits following an interstimulus interval shorter than 1400 msec. may reflect younger preschoolers' response to a previous stimulus.

Evaluation of algorithms for fire detection and mapping across North America from satellite

This paper presents an evaluation of advanced very high resolution radiometer (AVHRR)‐based remote sensing algorithms for detecting active vegetation fires [Li et al., 2000a] and mapping burned areas [Fraser et al., 2000] throughout North America. The procedures were originally designed for application in Canada with AVHRR data aboard the NOAA 14 satellite. They were tested here with both NOAA 11 and NOAA 14 covering the period 1989–2000. It was found that the active fire detection algorithm performs well with low commission and omission error rates over forested regions in the absence of cloud cover. Moderate errors were found over semi‐arid areas covered by thin clouds, as well as along rivers and around lakes observed from sun‐glint angles. A modification to a fire algorithm threshold and the addition of a new test can significantly improve the detection accuracy. Burned areas mapped by satellite were compared against extensive fire polygon data acquired by U.S. forest agencies in five western states. The satellite‐based mapping matches nearly 90% of total forested burned area, with the difference being mainly attributable to omission of some nonburned islands and patches within the fire polygons. In addition, it maps a significant area of burning outside the fire polygons that appear to be true fires. The 10% omission error was found to be caused mainly by three factors: lack or insufficient number of active fires, partial burning, and vegetation recovery after early season burning. In addition to total area, the location and shapes of burned scars are consistent with the ground‐based maps. Overall, the two algorithms are competent for detecting and mapping forest fires in North America north of Mexico with minor modifications.

Enduring effects of prenatal cocaine exposure on attention and reaction to errors.

Rats exposed to cocaine prenatally were administered a series of 3-choice visual attention tasks, with the most pronounced deficits seen in a task in which the onset time, location, and duration of a visual cue varied unpredictably between trials. The cocaine-exposed rats were less accurate than controls but did not differ in the rate of premature responses or omission errors. The pattern of errors, coupled with response latency data, implicated deficits in the ability to rapidly engage attention and maintain a high level of alertness to the task. The cocaine-exposed rats also exhibited a blunted reaction to an error on the previous trial, possibly reflecting an alteration in emotional regulation and/or error monitoring. Implications for underlying neuropathology are discussed.

Assessing Attention: Comparison of Response-Inhibition and Traditional Continuous Performance Tests

The purpose of this study was to compare a recently developed response-inhibition task (Conners, 1995) to slow- and fast-event-rate versions of the traditional A-X Continuous Performance Test (CPT). Among 146 normal adults, results revealed significant differences between tasks in omission and commission error rates, reaction time, reaction time variability, and responses to critical signals. Effects of environmental noise and participant anxiety also differed for the three tasks. Traditional CPTs produced time-related performance decrements, but the response-inhibition task produced improvement across initial blocks of trials. The response-inhibition task may measure executive control rather than sustained attention, and therefore may represent functions of different brain systems.

Interaction of semantic and perceptual processes in repetition blindness

Two experiments examined the effect of activation of higher-level semantic representations on lower-level perceptual representations. A forced-choice discrimination paradigm was used, a method known to produce repetition blindness (RB) for words unconfounded by memory demands or response bias. In Experiment 1, equivalent reductions in RB (as measured by omission error rate and by d') occurred when successive word pairs were identical in: (1) form, pronunciation, and meaning (both uppercase versions of the same word); (2) pronunciation and meaning but not form (lowercase versus uppercase; lexical identity); and (3) pronunciation, but not form or meaning (homonyms; phonological identity), relative to when the words were unrelated on all dimensions. The RB effect was markedly attenuated, but not eliminated, when the words were semantically related. Similar results were obtained in Experiment 2 using a larger group of subjects. These findings show that higher-order semantic representations can have a top-down influence on judgements based on lower-order perceptual representations. The results are discussed within the framework of a cascade model of object processing in the human brain.

Patterns of recovery of autonomic dysfunctions and neurocognitive deficits in schizophrenics after acute psychotic episodes.

In this study, the authors aimed to identify patterns of autonomic dysfunction and neurocognitive deficit recovery. The authors performed laboratory assessments on 66 patients with schizophrenia immediately after an acute psychotic episode and 6, 12, and 18 months later. Shortly after the psychotic episode, the patients displayed cardiovascular hyperarousal at rest, cardiovascular and electrodermal hyporeactivity during 2 Continuous Performance Tasks (CPTs) and deficits in 2 behavioral CPT measures (i.e., reaction time and omission error rate) compared with 29 normal controls. In the subsequent postpsychotic course, changes indicative of a process of recovery occurred in all measurement areas, although with regard to autonomic hyporeactivity amelioration was limited to a subgroup of schizophrenics with complete and persistent symptomatic remission. Neurocognitive improvement in CPTs did not appear to depend on unimpaired autonomic reactivity mechanisms.

Extracting Context-Sensitive Models in Inductive Logic Programming

Given domain-specific background knowledge and data in the form of examples, an Inductive Logic Programming (ILP) system extracts models in the data-analytic sense. We view the model-selection step facing an ILP system as a decision problem, the solution of which requires knowledge of the context in which the model is to be deployed. In this paper, “context” will be defined by the current specification of the prior class distribution and the client's preferences concerning errors of classification. Within this restricted setting, we consider the use of an ILP system in situations where: (a) contexts can change regularly. This can arise for example, from changes to class distributions or misclassification costss and (b) the data are from observational studies. That is, they may not have been collected with any particular context in mind. Some repercussions of these are: (a) any one model may not be the optimal choice for all contextss and (b) not all the background information provided may be relevant for all contexts. Using results from the analysis of Receiver Operating Characteristic curves, we investigate a technique that can equip an ILP system to reject those models that cannot possibly be optimal in any context. We present empirical results from using the technique to analyse two datasets concerned with the toxicity of chemicals (in particular, their mutagenic and carcinogenic properties). Clients can, and typically do, approach such datasets with quite different requirements. For example, a synthetic chemist would require models with a low rate of commission errors which could be used to direct efficiently the synthesis of new compounds. A toxicologist on the other hand, would prefer models with a low rate of omission errors. This would enable a more complete identification of toxic chemicals at a calculated cost of misidentification of non-toxic cases as toxic. The approach adopted here attempts to obtain a solution that contains models that are optimal for each such user according to the cost function that he or she wishes to apply. In doing so, it also provides one solution to the problem of how the relevance of background predicates is to be assessed in ILP.

Social cue perception in Japanese schizophrenic patients

Although abnormal social cue perception in schizophrenia is thought to be a factor in impairing the acquisition of social skills, there have been no studies on social cue perception in Japanese schizophrenics. In order to clarify the characteristics of social cue perception in Japanese schizophrenic patients, 46 schizophrenics and 41 normal controls were presented 12 videotaped vignettes of interpersonal situations, and then they were asked true–false questions about the interaction viewed. Additionally, schizophrenics were administered the Bech version of the Brief Psychiatric Rating Scale. The results showed that the schizophrenic group showed a poorer performance on the cue recognition task than the normal group, and in particular, schizophrenics exhibiting false alarm errors were seen more often than schizophrenics exhibiting omission errors. This suggests that false recognition of information that does not actually exist in social situation is an important characteristic of social cue perception in schizophrenic patients. The false alarm rates on the cue recognition task in schizophrenics were related to the severity of positive-thought disorder, but not to that of negative symptoms. There was no significant relationship between the omission error rates and the two symptom scores in schizophrenics. Faulty cue recognition and positive-thought disorder may be due to a common factor.

Empirical performance comparison of selective and constructive induction

The paper provides the results of a performance comparison study of two symbolic learning programs, both based on the AQ15c learning algorithm. The first program uses a single representation space, while the second one utilizes constructive induction, which changes the representation space. The performance of the compared systems was analyzed using three empirical error rates, including the overall, commission and omission error rates. These were determined by applying the hold-out, 10-fold, and leave-one-out sampling methods. Both systems' performance was calculated for individual stages in a multi-stage knowledge-acquisition process. Learning curves and their envelopes were prepared. The study was conducted using a set of 384 optimal designs of wind bracing in steel skeleton structures of tall buildings. The research methodology and the two learning systems used in the experiments are described, all numerical results are provided, and the conclusions of the research are given.

The extraction of phrase structure during reading: Evidence from letter detection errors

In light of recent suggestions regarding the prominence of structure in speech production and comprehension, it has been postulated that structural processing might also play a similarly important role in reading. Some evidence in support of this contention can be gleaned from eye-movement research. However, more systematic support comes from recent work on letter detection during reading, which has shown that the rate of omission errors is inordinately high for morphemes that disclose phrase structure. The results of three lines of research suggest that, early in text processing, readers attempt to extract a structural frame for the sentence to help the on-line integration of accessed representations, and that structure-supporting units recede to the background as the meaning of the sentence evolves.

Sensation seeking, paired associate learning and brain catecholamines.

Paired associate learning performance and strategies were analyzed in terms of learning situations (training vs. 'contextual' and 'noncontextual' transfer), personality factors [Thrill and adventure seeking (TAS) and disinhibition (Dis)] and catecholamine enzyme activity [dopamine-beta-hydroxylase (DBH) and monoamine-oxydase (MAO)]. Performance was better in transfer situations, in high MAO-high DBH subjects (high catecholamine turnover rate?), and as a negative function of DBH (preponderance of dopaminergic activity?). Error patterns of response selection (high omission and low intrusion error rate) were found to be a positive function of contextual transfer, TAS and DBH (high response-contingent noradrenergic activity?).

Left hemisphere's inability to sustain attention over extended time periods in schizophrenics.

Each hemisphere's ability to sustain attention over extended time periods was investigated in 14 schizophrenics and 17 controls using dichotic detection tasks. Schizophrenics produced significantly higher rates of omission errors, as compared to that of commission errors. The rates of omission errors for schizophrenics fluctuated markedly, while the rates of commission errors remained fairly constant. Primarily due to the fluctuation of omission errors, the detection index decreased progressively when schizophrenics were engaged in right-ear tasks. These results suggest that schizophrenics demonstrate a deficit concerning 'response set', especially in the left hemisphere. It is feasible that there may be a correlation with disturbances in integration mechanisms of both hemispheres in schizophrenics.

Studies on the regulation of sensitivity to the narcotic cue

This paper presents the results of two studies bearing on the problem of whether tolerance develops to the physiological actions underlying the discriminative stimulus properties of narcotic analgesic drugs. In the first study, rats were given daily non-contingent exposure to 0.06 mg/kg fentanyl for 30 days before they were trained to discriminate 0.04 mg/kg fentanyl from saline. In contrast with the predictions derived from the tolerance hypothesis it was found that, as compared with control (1) the omission error rate was decreased, (2) there was no increase in the number of sessions-to-criterion, (3) sensitivity to the narcotic cue was unaffected. The second study utilized rats with a long history of narcotic treatment; non-contingent exposure to increasing (0.06–0.16 mg/kg) fentanyl doses in addition to regular contingent exposure, failed to (i) increase the omission error rate, and (ii) to decrease sensitivity. It is concluded that the tolerance hypothesis is inadequate to account for the data reported here. An alternative hypothesis is proposed, asserting that the organism actively regulates its sensitivity to the physiological actions of narcotics, and that their biological significance presents a major source of feedback in this regulation.