The Perception of Involuntary Prosaccades in an Antisaccade Task

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 275-275
Author(s):  
A Mokler ◽  
B Fischer
Keyword(s):  
Error Rate ◽  
Reaction Times ◽  
Stimulus Onset ◽  
Error Rates ◽  
Data Sets ◽  
Antisaccade Task ◽  
Key Press ◽  
Extra Peak ◽  
The Mean ◽  
Strong Mode

In an antisaccade task subjects are required to generate a voluntary saccade to the side opposite to a small visual stimulus. With fixation-point offset preceding stimulus onset (gap) subjects produce some involuntary saccades to the stimulus and correct them by a second saccade. We wanted to know whether the subjects recognised their errors and whether a recognised sequence (error followed by correction) is different from an unrecognised sequence. To test the access to the correction mechanism, subjects were asked in subsequent experiments to produce the error-correction sequence voluntarily (voluntary sequence). We used the gap = 200 ms condition. A valid cue was presented 100 ms before stimulus onset. This manipulation increased the error rate (Fischer and Weber, 1996 Experimental Brain Research109 507 – 512). Subjects indicated errors by key-press. The rate of recognised and unrecognised errors, saccadic size, reaction times (SRT), and correction times (CRT) were determined. Altogether 93 data sets (400 trials each) from 38 subjects were analysed. The mean error rate was 20%, of which 62% went unrecognised. In sessions with high error rates the fraction of unrecognised errors was high. The SRT of the errors ranged from 80 to 170 ms with a strong mode of express saccades at 100 ms. Both types of errors had the same mean SRT of 117 – 119 ms. The unrecognised errors were 0.4 deg smaller. They were corrected after a mean CRT of 95 ms. The recognised errors were corrected after 127 ms; in the voluntary sequence the correction occurred after 217 ms. The CRT distributions differ from each other with the unrecognised errors having an extra peak around 45 ms, suggesting different modes of correction, to which perception has different access. These results raise the question why the large and long-lasting changes of the retinal image escape the conscious perception so often.

scholarly journals Another Warning about Median Reaction Time --- Version of 11 Feb 2020

2020 ◽  
Author(s):  
Jeff Miller
Keyword(s):  
Type I Error ◽  
Reaction Times ◽  
Error Rates ◽  
Type I ◽  
Experimental Conditions ◽  
Type I Error Rates ◽  
Correction Technique ◽  
Inflated Type ◽  
The Mean ◽  
Rt Distributions

Contrary to the warning of Miller (1988), Rousselet and Wilcox (2020) argued that it is better to summarize each participant’s single-trial reaction times (RTs) in a given condition with the median than with the mean when comparing the central tendencies of RT distributions across experimental conditions. They acknowledged that median RTs can produce inflated Type I error rates when conditions differ in the number of trials tested, consistent with Miller’s warning, but they showed that the bias responsible for this error rate inflation could be eliminated with a bootstrap bias correction technique. The present simulations extend their analysis by examining the power of bias-corrected medians to detect true experimental effects and by comparing this power with the power of analyses using means and regular medians. Unfortunately, although bias-corrected medians solve the problem of inflated Type I error rates, their power is lower than that of means or regular medians in many realistic situations. In addition, even when conditions do not differ in the number of trials tested, the power of tests (e.g., t-tests) is generally lower using medians rather than means as the summary measures. Thus, the present simulations demonstrate that summary means will often provide the most powerful test for differences between conditions, and they show what aspects of the RT distributions determine the size of the power advantage for means.

Localization–compensation algorithm based on the Mean kShift and the Kalman filter

2015 ◽  
Vol 29 (06n07) ◽  
pp. 1540020
Author(s):  
Dong Myung Lee ◽  
Tae Wan Kim ◽  
Yun-Hae Kim
Keyword(s):  
Kalman Filter ◽  
Error Rate ◽  
Mean Shift ◽  
Mobility Model ◽  
Mobile Node ◽  
Error Rates ◽  
Average Error ◽  
Compensation Algorithm ◽  
Average Error Rate ◽  
The Mean

In this paper, we propose a localization simulator based on the random walk/waypoint mobility model and a hybrid-type location–compensation algorithm using the Mean kShift/Kalman filter (MSKF) to enhance the precision of the estimated location value of mobile modules. From an analysis of our experimental results, the proposed algorithm using the MSKF can better compensate for the error rates, the average error rate per estimated distance moved by the mobile node ( Err _ Rate DV ) and the error rate per estimated trace value of the mobile node ( Err _ Rate TV ) than the Mean shift or Kalman filter up to a maximum of 29% in a random mobility environment for the three scenarios.

scholarly journals A variant of gravitational classification

2014 ◽  
Vol 51 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Tomasz Górecki ◽  
Maciej Luczak
Keyword(s):  
Gravity Field ◽  
Error Rate ◽  
Simulation Method ◽  
General Idea ◽  
Classification Error ◽  
Data Sets ◽  
Classification Error Rate ◽  
Motion Problem ◽  
The Mean ◽  
Parameter Values

Summary In this article there is proposed a new two-parametrical variant of the gravitational classification method. We use the general idea of objects' behavior in a gravity field. Classification depends on a test object's motion in a gravity field of training points. To solve this motion problem, we use a simulation method. This classifier is compared to the 1NN method, because our method tends towards it for some parameter values. Experimental results on different data sets demonstrate an improvement in efficiency and that this approach outperforms the 1NN method by providing a significant reduction in the mean classification error rate.

From Simple to Complex or Vice Versa: Sequence Effects on the Detection of Embedded Figures

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 247-247
Author(s):  
I Ludwig
Keyword(s):  
Reaction Time ◽  
Error Rate ◽  
Reaction Times ◽  
Random Order ◽  
Error Rates ◽  
Presentation Order ◽  
The Other ◽  
Embedded Figures ◽  
Sequence Effects ◽  
Mean Reaction Time

In a series of studies concerning part - whole perception we have investigated effects of perceptual learning, and of systematically varied presentation orders on the detection of embedded figures. In the present study the effects of increasing and decreasing complexity orders on detection performance are reported. Stimuli were 170 pairs of whole and part figures. Half of them were positive items, ie the searched part was contained in the (simultaneously presented) whole. The other half were negative items, ie the searched part was not contained in the whole. The difficulty of all figure pairs was determined from earlier data. On the basis of these difficulty parameters three presentation orders were created: (1) increasing difficulty (from simple to complex), (2) decreasing difficulty (from complex to simple), and (3) randomised order. Sixty subjects performed each of these tasks in three sessions separated by one week. Effects of practice and samples were balanced by permutating the order of the three tasks. The reaction times and error rates for all presentations were registered. The results showed marked differences between the three tasks: The lowest mean reaction time was obtained in the presentation order with increasing difficulty. Error rate, on the other hand, was lowest in the decreasing-difficulty presentation order. For the random-order presentation error rate and reaction time was in between the other orders. Furthermore, differences in benefit from practice were observed between the three orders of difficulty. Results are discussed with respect to the question of how efficient search strategies may be learned and whether one can learn to bend the rules of Gestalt organisation if required.

Continuous Wristband Monitoring Over 2 Years Decreases Identification Errors

2002 ◽  
Vol 126 (7) ◽  
pp. 809-815 ◽  
Author(s):  
Peter J. Howanitz ◽  
Stephen W. Renner ◽  
Molly K. Walsh
Keyword(s):  
Error Rate ◽  
Continuous Monitoring ◽  
The United States ◽  
Error Rates ◽  
Quality Of Services ◽  
Improvement Program ◽  
Monthly Basis ◽  
Number Of Patients ◽  
The Mean

Abstract Context.—Identification of patients is one of the first steps in ensuring the accuracy of laboratory results. In the United States, hospitalized patients wear wristbands to aid in their identification, but wristbands errors are frequently found. Objective.—To investigate if continuous monitoring of wristband errors by participants of the College of American Pathologists (CAP) Q-Tracks program results in lower wristband error rates. Setting.—A total of 217 institutions voluntarily participating in the CAP Q-Tracks interlaboratory quality improvement program in 1999 and 2000. Design.—Participants completed a demographic form, answered a questionnaire, collected wristband data, and at the end of the year, best and most improved performers answered another questionnaire seeking suggestions for improvement. Each institution's phlebotomists inspected wristbands for errors before performing phlebotomy and recorded the number of patients with wristband errors. On a monthly basis, participants submitted data to the CAP for data processing, and at the end of each quarter, participants received summarized comparisons. At the end of each year, participants also received a critique of the results along with suggestions for improvement. Main Outcome Measures.—The percentage of wristband errors by quarter, types of wristband errors, and suggestions for improvement. Results.—During 2 years, 1 757 730 wristbands were examined, and 45 197 wristband errors were found. The participants' mean wristband error rate for the first quarter in 1999 was 7.40%; by the eighth quarter, the mean wristband error rate had fallen to 3.05% (P < .001). Continuous improvement occurred in each quarter for participants in the 1999 and 2000 program and in 7 of 8 quarters for those who participated in both 1999 and 2000. Missing wristbands accounted for 71.6% of wristband errors, and best performers usually had wristband error rates under 1.0%. The suggestion for improvement provided by the largest number of best and most improved performers was that phlebotomists should refuse to perform phlebotomy on a patient when a wristband error is detected. Conclusions.—The wristband error rate decreased markedly when this rate was monitored continuously using the CAP Q-Tracks program. The Q-Tracks program provides a useful tool for improving the quality of services in anatomic pathology and laboratory medicine.

Saccadic and attentional abnormalities in patients with schizophrenia

1998 ◽  
Vol 28 (5) ◽  
pp. 1091-1100 ◽  
Author(s):  
P. MARUFF ◽  
J. DANCKERT ◽  
C. PANTELIS ◽  
J. CURRIE
Keyword(s):  
Chronic Schizophrenia ◽  
Stimulus Onset ◽  
Error Rates ◽  
Covert Attention ◽  
Visually Guided ◽  
Antisaccade Task ◽  
Attentional Shifts ◽  
Abnormal Performance ◽  
Onset Asynchrony ◽  
Normal Performance

Background. Abnormal performance on the antisaccade task suggests that patients with schizophrenia have difficulty with the inhibition of reflexive attentional shifts. The aim of the study was to investigate whether deficits in the inhibition of reflexive attentional shifts were specific to the oculomotor modality or whether they could also occur when attentional shifts were made without eye movements (e.g. covert attentional shifts).Methods. Fifteen medicated patients with chronic schizophrenia and 15 matched controls performed the antisaccade task and the covert orientating task (COVAT) where the probability of targets appearing at the same location of a peripheral cue was varied so that voluntary and reflexive orientating systems had the same goal (80% probability of target and cued condition) or opposite goals (20%probability of target at cued location). A condition where only reflexive orientating was initiated was also included (50% probability of target at cued location). For each of these conditions the stimulus onset asynchrony (SOA) varied between 150 and 350 ms.Results. Patients with schizophrenia showed normal latency and accuracy for visually guided saccades but increased error rates and latency on the antisaccade task. For the COVAT, patients with schizophrenia were unable to use voluntary orientating strategies to inhibit reflexive shifts of covert attention. On conditions where only reflexive orientating was required or when the goals of the reflexive and voluntary orientating systems were the same, patients with schizophrenia showed normal performance.Conclusions. These results suggest the reflexive orientating mode is normal in patients with chronic schizophrenia. However, these patients have a reduced ability to utilize the voluntary orientating mode to control or inhibit reflexive orientating. This impairment of voluntary control is evident for both overt and covert attentional shifts.

Perception of Hue Re-Examined: An Analytical Consideration of Color-Oddity Test Results

1977 ◽  
Vol 45 (3) ◽  
pp. 795-804 ◽  
Author(s):  
Angela C. Little ◽  
Rosslyn Gaines
Keyword(s):  
Multidimensional Scaling ◽  
Error Rate ◽  
Age Groups ◽  
Error Rates ◽  
Test Results ◽  
Chromaticity Diagram ◽  
Linear Transformations ◽  
Color System ◽  
The Mean ◽  
Theoretical Construction

The purpose of this study is to investigate an earlier finding wherein more than 100 subjects in four age groups responded systematically but differently to Munsell hues. According to the theoretical construction of the Munsell Color System, the spacing of the 10 hues is in perceptually equal intervals; the error responses to all hues at constant chroma should therefore be equal. The mean error rates were compared with Munsell hue distribution on seven linear and non-linear transformations of the International Commission on Illumination chromaticity diagram to uniform chromaticity systems. Hue intervals are not equal: red and green have the smallest intervals and largest error, and yellow and yellow-red the largest intervals and smallest error rate. These observations were substantiated by results from multidimensional scaling experiments reported elsewhere.

scholarly journals Computational dissociation of dopaminergic and cholinergic effects on action selection and inhibitory control

2019 ◽  
Author(s):  
Eduardo A. Aponte ◽  
Dario Schöbi ◽  
Klaas E. Stephan ◽  
Jakob Heinzle
Keyword(s):  
Inhibitory Control ◽  
Reaction Times ◽  
Action Selection ◽  
Error Rates ◽  
Antisaccade Task ◽  
Starting Point ◽  
Dose Dependent Fashion ◽  
The Cost ◽  
The Impact ◽  
Dose Dependent

AbstractBackgroundPatients with schizophrenia make more errors than healthy subjects on the antisaccade task. In this paradigm, participants are required to inhibit a reflexive saccade to a target and to select the correct action (a saccade in the opposite direction). While the precise origin of this deficit is not clear, it has been connected to aberrant dopaminergic and cholinergic neuromodulation.MethodsTo study the impact of dopamine and acetylcholine on inhibitory control and action selection, we administered two selective drugs (levodopa 200mg/galantamine 8mg) to healthy volunteers (N=100) performing the antisaccade task. A computational model (SERIA) was employed to separate the contribution of inhibitory control and action selection to empirical reaction times and error rates.ResultsModeling suggested that levodopa improved action selection (at the cost of increased reaction times) but did not have a significant effect on inhibitory control. By contrast, according to our model, galantamine affected inhibitory control in a dose dependent fashion, reducing inhibition failures at low doses and increasing them at higher levels. These effects were sufficiently specific that the computational analysis allowed for identifying the drug administered to an individual with 70% accuracy.ConclusionsOur results do not support the hypothesis that elevated tonic dopamine strongly impairs inhibitory control. Rather levodopa improved the ability to select correct actions. Instead, inhibitory control was modulated by cholinergic drugs. This approach may provide a starting point for future computational assays that differentiate neuromodulatory abnormalities in heterogeneous diseases like schizophrenia.

scholarly journals The Stochastic Early Reaction, Inhibition, and Late Action (SERIA) Model for Antisaccades

2017 ◽  
Author(s):  
Eduardo A. Aponte ◽  
Dario Schoebi ◽  
Klaas E. Stephan ◽  
Jakob Heinzle
Keyword(s):  
Decision Process ◽  
Model Comparison ◽  
Reaction Times ◽  
Error Rates ◽  
Decision Processes ◽  
Antisaccade Task ◽  
Data Set ◽  
Early Reaction ◽  
Experimental Findings ◽  
Reaction Inhibition

AbstractThe antisaccade task is a classic paradigm used to study the voluntary control of eye movements. It requires participants to suppress a reactive eye movement to a visual target and to concurrently initiate a saccade in the opposite direction. Although several models have been proposed to explain error rates and reaction times in this task, no formal model comparison has yet been performed. Here, we describe a Bayesian modeling approach to the antisaccade task that allows us to formally compare different models on the basis of their evidence. First, we provide a formal likelihood function of actions (pro- and antisaccades) and reaction times based on previously published models. Second, we introduce theStochastic Early Reaction, Inhibition, and late Action model(SERIA), a novel model postulating two different mechanisms that interact in the antisaccade task: an early GO/NO-GO race decision process and a late GO/GO decision process. Third, we apply these models to a data set from an experiment with three mixed blocks of pro- and antisaccade trials. Bayesian model comparison demonstrates that the SERIA model explains the data better than competing models that do not incorporate a late decision process. Moreover, we show that the race decision processes postulated by the SERIA model are, to a large extent, insensitive to the cue presented on a single trial. Finally, we use parameter estimates to demonstrate that changes in reaction time and error rate due to the probability of a trial type (prosaccade or antisaccade) are best explained by faster or slower inhibition and the probability of generating late voluntary prosaccades.Author summaryOne widely replicated finding in schizophrenia research is that patients tend to make more errors in the antisaccade task, a psychometric paradigm in which participants are required to look in the opposite direction of a visual cue. This deficit has been suggested to be an endophenotype of schizophrenia, as first order relatives of patients tend to show similar but milder deficits. Currently, most models applied to experimental findings in this task are limited to fit average reaction times and error rates. Here, we propose a novel statistical model that fits experimental data from the antisaccade task, beyond summary statistics. The model is inspired by the hypothesis that antisaccades are the result of several competing decision processes that interact nonlinearly with each other. In applying this model to a relatively large experimental data set, we show that mean reaction times and error rates do not fully reflect the complexity of the processes that are likely to underlie experimental findings. In the future, our model could help to understand the nature of the deficits observed in schizophrenia by providing a statistical tool to study their biological underpinnings.

Phonological and semantic activation in reading two-kanji compound words

2000 ◽  
Vol 21 (4) ◽  
pp. 487-503 ◽  
Author(s):  
AIKO MORITA ◽  
FUMIKO MATSUDA
Keyword(s):  
Stimulus Onset Asynchrony ◽  
Reaction Times ◽  
Stimulus Onset ◽  
Error Rates ◽  
Semantic Activation ◽  
Phonological Information ◽  
Semantic Interference ◽  
Compound Words ◽  
Phonological Interference ◽  
Onset Asynchrony

The purpose of this study was to examine whether phonological information was activated automatically in processing two-kanji compound words. In Experiment 1, 27 participants judged whether pairs of the words were homophones, while another 27 participants judged whether pairs were synonyms. Stimulus onset asynchrony (SOA) was 140 ms, 230 ms, or 320 ms. In Experiment 2, 36 participants were asked to make one of the two judgments, as in Experiment 1. SOA was determined individually. The following results were found. Reaction times showed semantic interference. Phonological interference was observed only under the shortest SOA in Experiment 2. Error rates showed phonological and semantic interferences even when SOA was the longest. These findings support the universal phonological principle.

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