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PubMed1983

Frequency discrimination and signal detection in band-reject noise.

An experiment was conducted in order to compare the importance of information from frequency regions remote from the nominal signal frequencies for frequency discrimination and signal detection. In both tasks, signals were presented within the "notch" of band-reject noise, and different notch widths were employed. The results indicate that information is integrated over a wider range in frequency discrimination than in signal detection. Further, experiments in which a noise floor was present as well as band-reject noise, indicate that disrupting the information from regions remote from the nominal signal frequencies impairs frequency discrimination even in the absence of any significant impairment of signal detection performance.

Auditory Perception↗
PubMed2003

"Nonparametric" A' and other modern misconceptions about signal detection theory.

Many modern descriptions of signal detection theory (SDT) are, at best, distorted caricatures of the Gaussian equal-variance model of SDT (G-SDT). The distortions have sometimes led to important, but unwarranted, conclusions about the nature of cognitive processes. Some researchers reject using d' and beta because of concerns about the validity of explicit underlying assumptions (that are shared with most inferential statistics), instead using either the supposedly "nonparametric" measures of A' and B" or measures known to confound ability and bias. The origins, development, and underlying assumptions of SDT are summarized, then contrasted with modern distortions and misconceptions. The nature and interpretation of common descriptive statistics for sensitivity and bias are described along with important pragmatic considerations about use. A deeper understanding of SDT provides researchers with tools that better evaluate both their own findings and the validity of conclusions drawn by others who have utilized SDT measures and analyses.

Decision Making↗
PubMed2000

Predicting individual false alarm rates and signal detection theory: a role for remembering.

The relationships between hit, remember, and false alarm rates were examined across individual subjects in three remember-know experiments in order to determine whether signal detection theory would be consistent with the observed data. The experimental data differed from signal detection predictions in two critical ways. First, remember reports were unrelated, or slightly negatively related, to the commission of false alarms. Second, both response types (remembers and false alarms) were uniquely related to hit rates, which demonstrated that the hit rate cannot be viewed as the result of a single underlying strength process. These results are consistent with the dual-process signal detection model of Yonelinas (1994), in which performance is determined by two independent processes--retrieval of categorical context information (remembering) and discriminations based on continuous item strength. Remember and false alarm rates selectively tap these processes, whereas the hit rate is jointly determined. Monte Carlo simulations in which the dual-process model was used successfully reproduced the pattern in the experimental data, whereas simulations in which a signal detection model, with separate "old" and "remember" criteria, was used, did not. The results demonstrate the utility of examining individual differences in response types when one is evaluating memory models.

Adult↗
PubMedDate not supplied

A brief primer on automated signal detection.

BACKGROUND: Statistical techniques have traditionally been underused in spontaneous reporting systems used for postmarketing surveillance of adverse drug events. Regulatory agencies, pharmaceutical companies, and drug monitoring centers have recently devoted considerable efforts to develop and implement computer-assisted automated signal detection methodologies that employ statistical theory to enhance screening efforts of expert clinical reviewers. OBJECTIVE: To provide a concise state-of-the-art review of the most commonly used automated signal detection procedures, including the underlying statistical concepts, performance characteristics, and outstanding limitations, and issues to be resolved. DATA SOURCES: Primary articles were identified by MEDLINE search (1965-December 2002) and through secondary sources. STUDY SELECTION AND DATA EXTRACTION: All of the articles identified from the data sources were evaluated and all information deemed relevant was included in this review. DATA SYNTHESIS: Commonly used methods of automated signal detection are self-contained and involve screening large databases of spontaneous adverse event reports in search of interestingly large disproportionalities or dependencies between significant variables, usually single drug-event pairs, based on an underlying model of statistical independence. The models vary according to the underlying model of statistical independence and whether additional mathematical modeling using Bayesian analysis is applied to the crude measures of disproportionality. There are many potential advantages and disadvantages of these methods, as well as significant unresolved issues related to the application of these techniques, including lack of comprehensive head-to-head comparisons in a single large transnational database, lack of prospective evaluations, and the lack of gold standard of signal detection. CONCLUSIONS: Current methods of automated signal detection are nonclinical and only highlight deviations from independence without explaining whether these deviations are due to a causal linkage or numerous potential confounders. They therefore cannot replace expert clinical reviewers, but can help them to focus attention when confronted with the difficult task of screening huge numbers of drug-event combinations for potential signals. Important questions remain to be answered about the performance characteristics of these methods. Pharmacovigilance professionals should take the time to learn the underlying mathematical concepts in order to critically evaluate accumulating experience pertaining to the relative performance characteristics of these methods that are incompletely defined.

Automation↗
PubMed2002

Atheroembolic signals detected by Doppler ultrasound scan monitoring in a patient with blue toe syndrome: report of a case.

It is generally accepted that clinical symptoms give the only clue to the presence of atheroemboli in patients with blue toe syndrome (BTS). We report a case of atheroemboli originating from the abdominal aortic aneurysm in which Doppler ultrasound successfully detected atheroembolic signals, which vanished immediately after surgery. To our knowledge, this is the first such case to be documented. When a 67-year-old man was given warfarin after aortocoronay bypass, digital cyanosis suddenly developed, which became worse and was very painful. Angiography and computed tomography scanning revealed an infrarenal aortic aneurysm with mural thrombus. Doppler ultrasound detected atheroemboli as high-intensity transient signals in the bilateral tibioperoneal trunks. After aneurysmectomy and a bifurcated graft replacement, the cyanotic and painful toes improved immediately. Microscopically, cholesterin crystals were seen in the arterioles of the amputated digits. Thus, Doppler ultrasound could be a valuable test to determine the appropriate treatment for patients at risk of atheroembolic BTS.

Aged↗
PubMed1997

Can we identify who will adhere to long-term physical activity? Signal detection methodology as a potential aid to clinical decision making.

Signal detection methodology was used to identify the best combination of predictors of long-term exercise adherence in 269 healthy, initially sedentary adults ages 50-65 years. Less educated individuals who were assigned to supervised home-based exercise of either higher or lower intensity and who were less stressed and less fit at baseline than other individuals had the greatest probability of successful adherence by the 2nd year. Overweight individuals assigned to a group-based exercise program were the least likely to be successful 2 years later. Predictors of short-term (1-year) adherence were generally similar to predictors of 2-year adherence. Signal detection analysis may be useful for identifying subgroups of people at risk for underadherence who subsequently might be targeted for intervention.

Aged↗
PubMed1988

Visual signal detection. IV. Observer inconsistency.

Historically, human signal-detection responses have been assumed to be governed by external determinants (nature of the signal, the noise, and the task) and internal determinants. Variability in the internal determinants is commonly attributed to internal noise (often vaguely defined). We present a variety of experimental results that demonstrate observer inconsistency in performing noise-limited visual detection and discrimination tasks with repeated presentation of images. Our results can be interpreted by using a model that includes an internal-noise component that is directly proportional to image noise. This so-called induced internal-noise component dominates when external noise is easily visible. We demonstrate that decision-variable fluctuations lead to this type of internal noise. Given this induced internal-noise proportionality (sigma i/sigma 0 = 0.75 +/- 0.1), the upper limit to human visual signal-detection efficiency is 64% +/- 6%. This limit is consistent with a variety of results presented in earlier papers in this series.

Acoustic Stimulation↗
PubMed1983

Signal detection and matching: analyzing choice on concurrent variable-interval schedules.

Pigeons' pecks on a red key and a green key were followed by access to grain according to pairs of concurrent independent variable-interval schedules in a combined signal detection/matching law paradigm. Pecks on the red key were reinforced by the richer variable-interval schedule if a short-duration tone had been presented; pecks on the green key were reinforced by the richer variable-interval schedule if a long-duration tone had been presented. Pecks on the green key given a short-duration tone, or on the red key given a long-duration tone, were reinforced by the leaner variable-interval schedule. The data were analyzed according to both signal detection's and the matching law's separate measures of, first, the discrimination of the choices and, second, the bias to make one response or another. Increasing the difficulty of the tone-duration discrimination decreased both methods' measures of the discrimination of the choices and did not change both methods' measures of the bias to make one response or another. Changing the leaner variable-interval schedule so that it approached the richer variable-interval schedule decreased signal detection's measure of discrimination but left its measure of response bias and the matching law measures unchanged. Data collected only until a subject's first changeover response following presentation of a long or a short tone showed higher values for both methods' measures of discrimination, no change in signal detection's measure of response bias, and lower values for the matching law's measure of response bias. Relationships between the matching law's and signal detection's methods of analyzing choice are discussed. It is concluded that a signal detection analysis is more efficient for examining changes in the difficulty of a discrimination, whereas a matching law analysis is more effective for examining the effects of changes in relative reinforcer frequency.

Animals↗
PubMed1982

Suggestions for altered auditory sensitivity, the negative subject effect and hypnotic susceptibility: a signal detection analysis.

Two experiments used signal detection procedures to assess the effects of hypnotic susceptibility, a hypnotic induction procedure, and suggestions for altering auditory acuity on measures of sensitivity and response bias. In Experiment 1, low susceptibles showed higher sensitivity than high susceptibles, and hypnotic induction failed to affect the sensitivity of either highs or lows. Among the high susceptibles, suggestions to either increase or decrease acuity produced increments in sensitivity and reduced individual differences. Thus, suggestions (regardless of the direction of change suggested) probably motivated highs who would have otherwise performed inefficiently to perform as efficiently as the low susceptibles. With respect to response bias, high-susceptible hypnotic subjects given a suggestion for increased acuity behaved in terms of suggested demands; they showed an increased tendency to response "signal." Low-susceptible hypnotic subjects given the same suggestion responded in a counterdemand or "negative subject" fashion; they developed a bias to say "noise." Experiment 2 used a more difficult discrimination task to replicate and extend this counterdemand effect in low susceptibles. Implications for hypnosis research and for research on the negative subject effect are discussed.

Auditory Perception↗
PubMed2001

A signal detection approach to the combined effects of work stressors on alcohol consumption.

OBJECTIVE: To test the relationship between work stress and alcohol consumption and the efficacy of signal detection analysis in a work stress-alcohol consumption study. METHOD: The study was part of a Work Site Health Project, which included a stress reduction program, at a manufacturing company in Osaka, Japan. The study design was a cross-sectional survey. The participants were Japanese male whitecollar workers (N = 457; 30 to 50 years old) in the head administrative office of a large manufacturing company. Measurements consisted of demographic variables of the workers (age, marital status, manner of living and Type A personality), work stress measures, working hours and alcohol consumption. RESULTS: Of eight independent variables, six significant predictors of heavy alcohol consumption were identified in the first signal detection analysis. Of these six variables, job demand and skill discretion were work-stress-related measures. In the second multiple regression analysis, skill discretion and job demand were significant predictors of alcohol consumption among the workers in two of the seven subgroups categorized by the first signal detection analysis. CONCLUSIONS: It was revealed that work stress did relate to alcohol consumption. However, the effect of the work stress upon alcohol consumption was limited to specific types of workers with multiple specific attributes. It was also inferred that the signal detection approach is an effective approach to the work stress alcohol consumption relationship.

Adult↗
PubMed1996

Signal-detection, threshold, and dual-process models of recognition memory: ROCs and conscious recollection.

Threshold- and signal-detection-based models have dominated theorizing about recognition memory. Building upon these theoretical frameworks, we have argued for a dual-process model in which conscious recollection (a threshold process) and familiarity (a signal-detection process) contribute to memory performance. In the current paper we assessed several memory models by examining the effects of levels of processing and the number of presentations on recognition memory receiver operating characteristics (ROCs). In general, when the ROCs were plotted in probability space they exhibited an inverted U shape; however, when they were plotted in z space they exhibited a U shape. An examination of the ROCs showed that the dual-process model could account for the observed ROCs, but that models based solely on either threshold or signal-detection processes failed to provide a sufficient account of the data. Furthermore, an examination of subjects' introspective reports using the remember/know procedure showed that subjects were aware of recollection and familiarity and were able to consistently report on their occurrence. The remember/know data were used to accurately predict the shapes of the ROCs, and estimates of recollection and familiarity derived from the ROC data mirrored the subjective reports of these processes.

Adult↗
PubMed1992

Single photon radioluminescence. II. Signal detection and biological applications.

A quantitative theory for excitation of fluorescent molecules by beta decay electrons is reported in the accompanying manuscript; experimental detection methods and biological applications are reported here. The single photon signals produced by an excited fluorophore (single photon radioluminescence, SPR) provide quantitative information about the distance between radioisotope and fluorophore. Instrumentation was constructed for SPR signal detection. Photons produced in a 0.5-ml sample volume were detected by a cooled photomultiplier and photon counting electronics. To minimize electronic noise and drift for detection of very small SPR signals, a mechanical light chopper was used for gated-signal detection, and a pulse height analyzer for noise rejection. SPR signals of approximately 1 cps were reproducibly measurable. The influence of inner filter effect, sample turbidity, and fluorophore environment (lipid, protein, and carbohydrate) on SPR signals were evaluated experimentally. SPR was then applied to measure lipid exchange kinetics, ligand binding, and membrane transport, and to determine an intermolecular distance in an intact membrane. (a. Lipid exchange kinetics.) Transfer of 12-anthroyloxystearic acid (12-AS) from sonicated lipid vesicles and micelles to vesicles containing 3H-cholesterol was measured from the time course of increasing SPR signal. At 22 degrees C, the half-times for 12-AS transfer from vesicles and micelles were 3.3 and 1.1 min, respectively. (b. Ligand binding.) Binding of 3H-oleic acid to albumin in solution, and 3H-2,2'-dihydro-4,4'-diisothiocyanodisulfonic stilbene (3H-H2DIDS) to band 3 on the erythrocyte membranes were detected by the radioluminescence of the intrinsic tryptophans. The SPR signal from 5 microCi 3H-oleic acid bound to 0.3 mM albumin decreased from 13 +/- 2 cps to 3 +/- 2 cps upon addition of nonradioactive oleic acid, giving 2.7 high affinity oleic acid binding sites per albumin. The SPR signal from 1 microCi 3H-H2DIDS bound selectively to erythrocyte band 3 in erythrocyte ghosts (1.5 mg protein/ml) was 2.2 +/- 0.8 cps. (c. Membrane transport). Dilution of J774 macrophages loaded with 3H-3-O-methylglucose and BCECF gave a decreasing SPR signal with a half-time of 81 s due to methylglucose efflux; the SPR measurement of the efflux rate was in agreement with a conventional tracer efflux rate determination by filtration. 20 microM cytochalasin B inhibited efflux by 97%. (d. Distance determination.) The SPR signal from erythrocyte membranes labeled with 27 microCi 3H-oleic acid and 10 microM of fluorescein-labeled wheat germ agglutinin was 5.7 +/- 0.5 cps, giving an average glycocalyx-to-bilayer distance of 5 nm. The results establish methods for experimental detection of SPR signals and demonstrate the applications of radioluminescence to the measurement of lipid exchange kinetics, ligand binding, membrane transport, and submicroscopic distances in intact membranes in real time.

Biophysical Phenomena↗
PubMed2002

Signal detection theory, detectability and stochastic resonance effects.

Stochastic resonance is a phenomenon in which the performance of certain non-linear detectors can be enhanced by the addition of appropriate levels of random noise. Signal detection theory offers a powerful tool for analysing this type of system, through an ability to separate detection processes into reception and classification, with the former generally being linear and the latter always non-linear. Through appropriate measures of signal detectability it is possible to decide whether a local improvement in detection via stochastic resonance occurs due to the non-linear effects of the classification process. In this case, improvement of detection through the addition of noise can never improve detection beyond that of a corresponding adaptive system. Signal detection and stochastic resonance is investigated in several integrate-and-fire neuron models. It is demonstrated that the stochastic resonance observed in spiking models is caused by non-linear properties of the spike-generation process itself. The true detectability of the signal, as seen by the receiver part of the spiking neuron (the integrator part), decreases monotonically with input noise level for all signal and noise intensities.

Humans↗
PubMedDate not supplied

Signal detection theory and the psychophysics of pain: an introduction and review.

A brief explanation of signal detection theory is presented, followed by a review of the literature in which differences in pain report were analyzed to determine if changes were in sensitivity (physiological processes) or in response bias (a subject's willingness to report that a signal occurred). Three kinds of studies are reviewed: modification, procedural, and comparative and normative. The advantages of using a signal detection approach in pain research are emphasized. It is concluded that experimenters applying signal detection analysis to pain research should give greater consideration to methodological procedures and be cognizant of all possibilities for shifts in sensitivity (d)'.

Acupuncture Therapy↗
PubMed1996

Visual signal detection in structured backgrounds. I. Effect of number of possible spatial locations and signal contrast.

Several studies have investigated the effect of signal location uncertainty on the detectability of simple visual signals in uncorrelated Gaussian noise with a deterministic background. For this case, human performance in locating a signal in a forced-choice experiment has been successfully predicted for 2-1800 alternative locations with the use of signal detection theory and the usual assumption that the observer's internal response is Gaussian distributed. Gaussian uncorrelated noise is far from realistic medical image noise, which includes not only fluctuations in intensity of quantum origin but also other anatomical objects lying in the x-ray path (structured backgrounds). Our goal is to determine whether signal detection theory with the Gaussian assumption is adequate for the case of structured backgrounds, or whether other more complex models need to be developed to predict human performance as a function of the number of possible signal locations in structured backgrounds. We present experimental data suggesting that an assumed Gaussian internal response accurately predicts the decrease in observer performance as the number of alternative locations is increased. The one exception is a lower-than-predicted performance for the detection of low-contrast signals for two alternative locations. Performance as measured by the index of detectability d' is also found to be linear with signal contrast. Together these findings extend the applicability of signal detection theory with Gaussian internal response functions to the case of complex structured backgrounds.

Computer Simulation↗
PubMed1997

Signal detection and pitch ranking in conditions of masking release.

Masked threshold levels for signal detection or pitch ranking (low, middle, or high) were determined in conditions where one of three possible signal frequencies could be presented on a given trial of a three-interval forced-choice task. Thresholds were determined under conditions investigating binaural masking release (the masking-level difference, or MLD) and monaural masking release in modulated noise. It was assumed that part of the masking release in modulated noise was due to a within-channel analysis of information in the masker dips, and that part of the masking release was due to across-frequency analysis of temporal envelope information (comodulation masking release, or CMR). In the MLD experiment, the masker was a low-pass noise with a frequency cutoff of 1000 Hz. In the modulated-noise experiment, a broadband noise was square-wave amplitude modulated at a rate of 25 Hz and then digitally low-passed filtered at 1000 Hz. The results indicated that when the frequency separation between frequency components was relatively wide, masking release for pitch ranking was similar to that for signal detection. However, as the frequency separation between components narrowed, masking release for pitch ranking decreased. The results are consistent with an interpretation that information regarding signal frequency is relatively coarse under the conditions of masking release examined here.

Adult↗
PubMed2005

A signal detection analysis of contingency data.

There are many psychological tasks that involve the pairing of binary variables. The various tasks used often address different questions and are motivated by different theoretical issues and traditions. Upon closer examination, however, the tasks are remarkably similar in structure. In the present paper, we examine two such tasks, the contingency judgment task and the signal detection task, and we apply a signal detection analysis to contingency judgment data. We suggest that the signal detection analysis provides a novel interpretation of a well-established but poorly understood phenomenon of contingency judgments--the outcome-density effect.

Adult↗
PubMed2004

[Stochastic resonance in weak signal detection by sensory systems].

OBJECTIVE: To study the stochastic resonance phenomenon in biological sensory systems through signal detection theories and psychophysical experiments. METHOD: Sensory system is considered as threshold detectors including the receiver part and the classifier part. Compared with conventional models regarding the receiver part of the sensory system as a linear or single non-linear system, a summing network constructed by MacCulloch-Pitts neurons was provided in our model to simulate the receiver part. RESULT: The simulation results showed that the relevant indices of the percent correct measure and the detectability of signal both exhibit stochastic resonance behaviors. Psychophysical experiments were carried out through both 1IFC (one interval forced choice) and 2IFC (two interval alternative forced choice) methods. The experimental results qualitatively verified the considerations in accordance with the theoretical model. CONCLUSION: This work gives a proof that stochastic resonance is not only an epiphenomenon in sensory systems.

Models, Neurological↗