Spurious Patterns Research Articles

Observer effects and training in underwater visual surveys of reef fishes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 154:53-63 (1997) - doi:10.3354/meps154053 Observer effects and training in underwater visual surveys of reef fishes Thompson AA, Mapstone BD Visual survey techniques are used widely to estimate abundances of target organisms in terrestrial and aquatic environments. There are a number of methodological 'errors' in almost all applications of visual surveys. Given the dependence of all visual survey data on the skill and technique of the observer, one potentially important source of imprecision and/or bias is variation among and within observers. In studies involving large amounts of fieldwork over great geographic range and many years, it is inevitable that observers will change from place to place and through time at any single site as they are replaced or gain experience. We present the results of 3 observer training/calibration exercises that indicate that observational studies in which multiple observers must be employed may be subject to considerable observer-related biases and imprecision. We found that careful training and calibration of observers ameliorated such effects for most taxa, but non-trivial levels of bias for some taxa and imprecision in estimates for several taxa remained even after thorough training. It is essential that the influence of observer bias and imprecision be well documented in multi-observer monitoring studies, so that (spurious) patterns related to differences among observers can be distinguished from real spatial or temporal patterns in the environment. Observer training · Bias · Precision · Monitoring · Visual survey · Fish counts Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 154. Publication date: July 31, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Singular Value Decomposition Analysis and Canonical Correlation Analysis

The goal of singular value decomposition analysis (SVD) and canonical correlation analysis (CCA) is to isolate important coupled modes between two geophysical fields of interest. In this paper the relationship between SVD and CCA is clarified. They should be considered as two distinct methods (possibly) suitable for answering two different questions. Some problems associated with interpreting results of both SVD and CCA are discussed. Both methods have a high potential to produce spurious spatial patterns. Caution is always called for in interpreting results from either method.

Formation of dislocation patterns: Computer simulations.

Dislocations patterns have been extensively studied by means of TEM. In parallel, theoretical approaches have been developed by using two methods; reaction diffusion schemes and computer simulation models. This distinction is not rigid since some computer models include the former approach in their evolution equations. Independently from the difficulties each approach presents in formulating the collective behavior of dislocations, the aim of these studies is to exhibit simple dislocation patterns as persistent slip bands and/or cellular organization. In this context, computer simulations brought a methodology which undoubtedly is a complement to the existing approaches for dislocations. Nevertheless, several remarks must be pointed out about the results obtained with the method. First, the conditions of simulations (e.g., cutoff procedure, periodic boundaries conditions), have been extensively criticized and responsible for spurious patterns. Second, the simulations developed do not show clearly the formation of cell structures. Third, the simulations performed do not tell us about the evolution of dislocation patterns in function of the parameters such as dislocation density, external force, or friction stress. The aim of the simulations presented here is to study at the mesoscopic scale the formation of dislocation patterns in two dimensions. For this, we used systems of large dimensions (20\ensuremath{\mu}${)}^{2}$ and rigid boundaries conditions which permitted us to avoid a cutoff procedure. The simulations performed exhibit the formation of dipolar walls present in persistent slip bands and clearly show the formation of cell organizations. For each pattern observed, we have deduced relationships between the size of the patterns and the parameters used as dislocation density, external force, or friction stress. And indeed, the results obtained show a good agreement with experimental laws. \textcopyright{} 1996 The American Physical Society.

Orthodox Religious Beliefs and Anti-Semitism: A Replication of Glock and Stark in the Netherlands

The Glock and Stark theoretical framework on Christian beliefs and anti-Semitism implies that orthodox religious beliefs perpetuate secular anti-Semitism via particularism and religious anti-Semitism. Several critics have argued that the major weakness of this study is its failure to examine explanatory variables other than religious beliefs. This paper addresses these issues using data from a 1990-91 national Dutch survey. Although the results tend to support the assumption that nonreligious variables are far more important to the explanation of anti-Semitism and, too, that they attenuate the impact of Christian orthodoxy, the effects of the latter are by no means spurious. The most important conclusion of this paper is therefore that there still is, in Holland at least, a religious factor at work, albeit a modest one, generating anti-Semitic beliefs. Numerous studies have documented that people who consider themselves to be Christians are more likely to be anti-Semitic than those who are not religious. Despite the large amount of data that has been collected on this issue, however, the problem of whether and, if so, how and to what extent Christian religion per se engenders less compassion for Jews has never really been solved. Ambiguity remains because most studies have not been theory-guided, and consequently their findings were purely ad hoc. Further, in studying religion and its role in supporting anti-Semitism, one must always consider the possibility that nonreligious variables may create spurious patterns of relationships. Relatively little research has yet been done, however, to determine their confounding influences in order to support or challenge the assumption - held by many but made explicit by a few - that the Christian churches are conducive to anti-Jewish sentiments in their members. This paper examines the role orthodox Christian beliefs play in religious and secular anti-Semitism in the Netherlands, using data from a 1990-91 national Dutch survey. The study was triggered by the recent revival of hostility towards Jews across much of western Europe. Many of those who try to understand this upsurge emphasize anti-Semitic prejudice deeply entrenched within European Christian culture and history as the core of the problem. We therefore decided to examine whether vestiges of this legacy remain in Holland to

Investigating feedforward neural networks with respect to the rejection of spurious patterns

The reliability of feedforward neural networks with respect to the rejection of patterns not belonging to the defined training classes is investigated. It is shown how networks with different activation functions and propagation rules construct the decision regions in the pattern space and, therefore, affect the network's performance in dealing with spurious information. A modification to the standard MLP structure is described to enhance its reliability in this respect.

A fault diagnosis prototype for a bioreactor for bioinsecticide production

Abstract The objective of this work is to develop an algorithm for fault diagnosis in a process of animal cell cultivation, for bioinsecticide production. Generally, these processes are batch processes. It is a fact that the diagnosis for a batch process involves a division of the process evolution (time horizon) into partial processes, which are defined as pseudocontinuous blocks. Therefore, a PCB represents the evolution of the system in a time interval where it has a qualitative behavior similar to a continuous one. Thus, each PCB, in which the process is divided, can be handled in a conventional way (like continuous processes). The process model, for each PCB, is a Signed Directed Graph (SDG). To achieve generality and to allow the computational implementation, the modular approach was used in the synthesis of the bioreactor digraph. After that, the SDGs were used to carry out qualitative simulations of faults. The achieved results are the fault patterns. A special fault symptom dictionary —SM—has been adopted as data base organization for fault patterns storage. An effective algorithm is presented for the searching process of fault patterns. The system studied, as a particular application, is a bioreactor for cell cultivation for bioinsecticide production. During this work, we concentrate on the SDG construction, and 3btaining real fault patterns by the elimination of spurious patterns. The algorithm has proved to be effective in both senses, resolution and accuracy, to diagnose different kinds of simulated faults.

Redshift data and statistical inference

Frequency histograms and the 'power spectrum analysis' (PSA) method, the latter developed by Yu & Peebles (1969), have been widely employed as techniques for establishing the existence of periodicities. We provide a formal analysis of these two classes of methods, including controlled numerical experiments, to better understand their proper use and application. In particular, we note that typical published applications of frequency histograms commonly employ far greater numbers of class intervals or bins than is advisable by statistical theory sometimes giving rise to the appearance of spurious patterns. The PSA method generates a sequence of random numbers from observational data which, it is claimed, is exponentially distributed with unit mean and variance, essentially independent of the distribution of the original data. We show that the derived random processes is nonstationary and produces a small but systematic bias in the usual estimate of the mean and variance. Although the derived variable may be reasonably described by an exponential distribution, the tail of the distribution is far removed from that of an exponential, thereby rendering statistical inference and confidence testing based on the tail of the distribution completely unreliable. Finally, we examine a number of astronomical examples wherein these methods have been used giving rise to widespread acceptance of statistically unconfirmed conclusions.

A robotic vision system for object identification and manipulation using synergetic pattern recognition

This paper discusses the application of the synergetic pattern recognition method to a robotic vision system for workpiece identification and manipulation in automated flexible manufacturing environments. The original synergetic algorithm is extended to allow its pattern attention parameters to have different values. Stability analysis of the extended recognition model indicates that the prototype patterns are the only stable patterns and undesired spurious patterns cannot exist. A simple scheme for tuning attention parameters is developed. Simulation results show that the number of object misclassification is reduced significantly with this extension. In addition, an image preprocessing procedure enables synergetic recognition to be simultaneously invariant to spatial pattern translation, rotation, and scaling; while an approach for recovering position, orientation, and size information is also proposed. Simple and efficient task-directed and object-specific strategies for robotic workpiece manipulation are now easy to implement based on these results and procedures.

The Analysis and Interpretation of Seedling Recruitment Curves

We present statistical methods appropriate for the analysis of seedling recruitment data. The techniques are applied to the data collected by H. A. Roberts and his colleagues. The main result of this analysis is that seed banks do not in general decay according to a negative exponential pattern and that a wide range of recruitment patterns occur. We explore the effects of unobserved mortality on age-specific recruitment. We also demonstrate the difficulty of interpreting age-specific patterns of recruitment in terms of the behavior of individual seeds. This difficulty is a result of unobserved seed mortality and between-seed variability, either of which can qualitatively change the shape of the recruitment curve. A simple model of the recruitment process is presented, and it is demonstrated that density dependence can generate spurious patterns of age-specific recruitment.

Empirically derived model of the role of sleep in associative learning and recuperative processes

Abstract Neuronal firing patterns, defined as intraburst temporal relations between sequential spike intervals, were monitored extracellularly from the rostral part of the nucleus reticularis (NR) and from the centrum medianum—parafascicular complex (CM-Pf) of the thalamus in adult freely moving cats during acquisition of bar pressing behavior (BP1) for milk reward, subsequent slow wave sleep (SWS1), and contiguous rapid eye movement (REM1) sleep, and then, 16 to 48 h later, after the animal fully learned the conditioned BP behavior (BP2). The patterns were defined on the basis of relative relations between sequential spike intervals. The intervals were compared in sequential pairs, moving one interval at a time. This method, if applied to random and/or independent values, generates a novel and well-defined theoretical distribution of inequality patterns which is uniquely sensitive to the history of spike train and plastic changes at neuronal membrane. The “information” encoded in single neuronal firing patterns was quantified using two criteria: (a) the magnitude of pattern emissions with reference to the random model; and (b) the difference between pattern distribution during BP1-training/acquisition and after the animal fully acquired the BP behavior. The latter patterns, termed BP2-template, were assumed to be composed only of patterns relevant for learned behavior. Thus, other patterns observed during BP-1, SWS, and REM were classified as spurious. During BP-1 training/acquisition of conditioned behavior, in 28 out of 265 neurons studied, the firing patterns linked to and relevant for BP behavior emerged in background of spurious patterns. Subsequently, during SWS-1, the relevant patterns were selectively suppressed below chance level. Conversely, during REM-1 sleep, contiguous with SWS-1, patterns linked to acquisition of BP behavior were strongly amplified above the level observed during BP1-training episode, while the ‘spurious’ patterns were eliminated. Thus, REM-1 patterns may be regarded as amplified precursors of the BP2-template which, 16 to 48 h later, and often after additional training, emerged with the acquired conditioned BP behavior. With reference to the random model, the emission magnitudes of individual BP-1 patterns were correlated with suppressions of same patterns during subsequent SWS-1. The magnitudes of these deficits were, in turn, correlated with subsequent REM1-induced amplified emission of same patterns. These observations indicate that: (a) acquisition of operantly conditioned behavior is linked to inversions in statistical distribution of patterns during BP1, SWS1, and REM1 episodes; and (b) the inversions are not random but graded, and therefore are likely to reflect the well-known graded nature of receptor desensitization which may result from repetitive exposure to neurotransmitters and/or modulators during a motor task that requires repetitive use of the same set of neuronal assemblies and pathways over a significant period of time. The neuronal firing patterns in “control” episodes of milk drinking from a bowl (BOWL) had, on the average, no significant relationships to BP, SWS, nor REM episodes. The results provide: (a) a novel insight into the information processing based on intraburst temporal organization of spike trains, as opposed to the mean firing rate; (b) a novel concept of homeostatic behavior of neurons which is consistent with current views on the physico-chemical dynamics of neuronal membrane and its receptors; (c) the first quantifiable empirical evidence for the relationships between firing patterns, learning, SWS, and REM sleep; and (d) the results suggest a new model for learning linked to recuperative role of sleep which is based on spatio-temporal inversion of neuronal interactions and depolarization-induced recovery (DIR) of synaptic receptors that had been down regulated during waking state. This notion is compatible with receptor changes in vitro and in vivo.

Neural network architectures for content-addressable memory

The paper investigates whether neural network content-addressable memories (CAMs) can compete with the non-neural alternatives which are currently available. The storage and retrieval of 64-bit patterns is used as a test problem which reflects the requirements of today's computer technology. The two main strategies available for implementing a CAM with a neural network architecture, feedback networks and twostage CAMs, and in particular their ability to retrieve patterns from corrupted input data, are investigated in detail. The storage capacity of the Hopfield network is very poor although it can be improved with the use of an iterative algorithm, such as the threshold algorithm which is described in this paper. However, the possibility of generating spurious patterns always remains with feedback networks. Two-stage CAMs are much more efficient, provided that an appropriate algorithm is used for the input classification stage. The wellknown perceptron and least-mean squares algorithms need to be modified if they are to cope with corrupted input patterns, but the optimal classifier for the type of problem under consideration is the minimum-distance classifier (or Hamming network for binary patterns). The implementation of the latter in analogue VLSI is discussed in the last section of the paper as an alternative to conventional technology.

There's No Percentage in It: Intersite Spatial Analysis of Bushman (San) Pottery Decorations

Grass-tempered bowls made by the forbears of historical Karoo Bushmen between ca. A.D. 1500 and 1800 were decorated with many different stamp-impressed motifs. Five of the seven observed motif groups appear to be distributed randomly across the 2,000 km2 study area in the upper Seacow River valley, South Africa. When their percentage frequencies per site cluster were mapped, however, localized concentrations appeared. The validity of the percentage concentrations is tested here by unconstrained cluster analysis, which is not subject to the closure effect. Also, several other tests, all avoiding the use of percentage frequency maps, are introduced as alternative ways to deal with unevenly distributed sites and scarce artifacts or traits unevenly distributed among the sites themselves. The results demonstrate that percentage-frequency mapping can produce occasionally spurious and misleading patterns. Because stratigraphic evidence is scarce and inconclusive, and direct dating of sherds has not yet been conducted, a test also is proposed for determining contemporaneity of motif groups.

Comparative Synoptic Dynamics. I. Relationships Between Inter- and Intra-Specific Spatial and Temporal Variance/Mean Population Parameters

SUMMARY (1) In an initial analysis, the inter- and intra-specific relationships between spatial and temporal variances and means are examined comparatively within and between ninety-seven aphid, 263 moth and eighty-four bird species at up to 300 sites for about a decade throughout Great Britain. (2) Despite the vast amount of data available, from which more than half the species sampled had been removed before analysis because they were numerically inadequate, parameter bias remains in some species and results in interspecific artifacts. (3) Population parameters dependent on small samples with arithmetic means below two and variances below four, are subject to distortion affecting all measures of aggregation. The artifact of small discrete samples is illustrated by spurious patterns in the relationship between log mean and log variance. (4) In contrast, taxonomic defects in the data were discovered by inconsistencies in the analysis of spatio-temporal pattern because of the large numbers of species sampled simultaneously.

Moire Pattern in Color Television

The overlapping of two periodic line patterns of the same general magnitude can produce larger scale visible patterns called moire fringes. In shadow mask picture tubes a design objective is to prevent such unsought patterns from being produced by the interaction of the scan line pattern with the pattern of mask holes or phosphor dots. This goal is the subject of this paper, although a broader examination of moire in color television would include other spurious patterns in the reproduced picture. These could be caused by interference between two or more patterns such as the original subject, the target grid of the image orthicon, scan line pattern, mask-screen pattern, and carrier color signal periodicity.

Experiments in Bright-Field Imaging with Hollow-Cone Illumination

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.

Transient gas‐liquid flow in horizontal pipes: Modeling the flow pattern transitions

AbstractThe theory for predicting flow pattern transition under transient flow conditions is developed and compared with experiment. This work represents an extension of the methods presented by Taitel and Dukler (1976) for steady state flows. Under transient conditions, flow pattern transitions can take place at flow rates substantially different than would occur under steady flow conditions. In addition, flow patterns can appear which would not be expected for a slow change in flow rates along that same path. Methods are presented for predicting the flow rates at which flow pattern transitions will take place during flow transients. The method also reveals when spurious flow patterns will appear.

Identification of a potential artifact in the use of electron microscope autoradiography to localize saturated phospholipids in cells

The suitability of electron microscope autoradiography for sutdying the uptake and intracellular localization of lipid vesicles (liposomes) containing radiolabeled saturated phospholipids has been examined. Data are presented showing that preparation of specimens for electron microscope autoradiography by conventional methods is accompanied by significant translocation and intercellular redistribution of radiolabeled saturated lipids, causing spurious labeling patterns. Intercellular redistribution of radiolabeled lipid was demonstrated by mixing glutaraldehyde-fixed mous L1210 cells that had been incubated with sonicated lipid vesicles containing [H] dipalmitoyl phosphatidylcholine with an indicator cell population (fixed avian erythrocytes) which had not been exposed to vesicles and showing that after electron microscope processing radiolabeled grains were present in both cell types. The same redistribution artifact also probably affects the intracellular localization of radiolabeled lipids. This artifact is discussed in relation to previous work in which autoradiographic methods have been used for ultrastructural localization saturated phospholipids in cells and tissues.

Pitfalls in the study of steady state kinetics of enzymes: Spurious inhibition patterns due to stray light errors

Abstract When reaction velocity measurements of enzyme reactions are carried out with single beam, single monochromator spectrophotometers, stray light in the spectrophotometer can produce systematic errors in the apparent velocities when highly absorbing solutions (optical density >2.0) are used. These errors can give rise to spurious “inhibition” patterns of the steady state kinetics. Because of a suspected error of this kind, this laboratory has recently reinvestigated the kinetics of glucose 6-phosphate dehydrogenase from Escherichia coli and found that the reported noncompetitive inhibition of the enzyme by DPNH is explained more readily by an unnoticed effect of stray light on the apparent reaction velocity than by a true enzyme inhibition. Methods for estimating and correcting such errors in spectrophotometers are presented in detail.

Luminance thresholds for subjective patterns in a flickering field: effect of wavelength.

When a uniform field is intermittently illuminated, it will often appear to contain various geometric patterns. The present study deals with the threshold luminance at which such spurious patterns appear and with the dependence of this threshold upon the frequency of intermittency and upon the wavelength of the stimulus. The log threshold luminance increases roughly linearly with the frequency of intermittency over the major part of the frequency range tested. The threshold is affected by stimulus wavelength; blue or green require higher luminances than yellow or red. However, these differences of threshold vary with frequency of intermittency and reach maxima at approximately 14 cps. The wavelength effects are modified by chromatic preadaptation.

Causal Models and Probability

Elementary probability statements are employed in causal inference models as an alternative to Blalock's correlation technique. By making use of certain simplifying assumptions, surplus equations become available for predictive use. Probability statements and predictions are shown for one-way causal models with causal chain, possibly spurious, and convergent patterns of relations. Fictitious data are used to illustrate the feasibility of probability models. Probability models thus provide another perspective for the kinds of causal models considered by Blalock. B lalock has extended and refined a technique for making causal inferences from correlational data based on earlier work by Simon.' This technique, in essence, requires explicit assumptions about the presence and direction of causal connections among a specific set of variables treated as a closed system. Zero-order and partial correlation coefficients-or beta coefficients-are computed for one or more specific models to help determine whether predicted relationships obtain. A particular model is retained as a possible causal explanation, if predictions are confirmed. Otherwise a model is rejected. This paper takes the position that probability statements may be used in causal inference models as an alternative to correlation or beta coefficients. If probability statements can serve as a substitute kind of measure, as the following discussion indicates, then we have a different set of analytic procedures for tackling problems of causal inference. Attention will be limited in this paper to (1) specifying the kinds of predictions that can be made for certain basic patterns of relationships among variables in threeand four-variable models, (2) illustrating the feasibility of causal probability models, and (3) noting similarities and differences between probability statements and correlation coefficients in causal models. A basic requirement in developing strategy and techniques for handling causal models is to establish prediction equations. In approaching this task we can briefly note some similarities between probability statements and correlation coefficients. First, in one-way causal models, statements of relationship must be asymmetric. This is accomplished by establishing a system of recursive equations in Blalock's approach and can be attained in a similar manner for probability models. Second, simplifying assumptions are necessary in order to have one or more excess equations for predictive purposes. Prediction equations become available partly as a result of assuming that certain variables in the model are unrelated. Thus a zero correlation can be predicted in using Blalock's technique as compared with a prediction of independence with the probability approach. Third, some predictions require controls for other variables in a model that may influence certain relations. In comparison with partial coefficients, conditional probability statements achieve this end in a slightly different manner, as subsequent discussion will show. Blalock's position on the concept of causality can be accepted as a working basis for the following discussion.2 In brief, this posi* Revised version of a paper presented at the annual meeting of the Southern Sociological Society, Atlanta, Georgia, April 1965. 1 See Hubert M. Blalock, Jr., Causal Inferences in Nonexperimental Research (Chapel Hill: The University of North Carolina Press, 1964), and Herbert A. Simon, Spurious Correlations: A Causal Interpretation, Journal of the American Statistical Association, 49 (September 1954), pp. 467479. 2 For a discussion of this position, see Hubert M. Blalock, Jr., Four-Variable Causal Models and Partial Correlations, American Journal of Sociology, 68 (September 1962), p. 183, and Blalock, op. cit., pp. 3-26. This content downloaded from 157.55.39.104 on Sun, 19 Jun 2016 05:53:26 UTC All use subject to http://about.jstor.org/terms