Non-target Patterns Research Articles

Variational learning in L2

This study examines the interpretation of constituent wh-questions in L2 English by learners whose L1 is Austrian German. Austrian German and English share identical surface word order patterns for a range of question forms, but with distinct semantic interpretations. Non-target patterns of interpretation show that the learners ay high levels of proficiency continue to optionally parse English questions with the L1 syntax. The continued presence of thematic verb movement and head-final VP syntax in L1 German-L2 English interlanguage challenges previous findings that headedness is reset very early and that V2 is realised by auxiliary verbs. This is analysed as an instance of Variational Learning (Yang, 2002), whereby the L1 grammar is accessed to parse L2 input where possible. The L1 syntactic representation thus continues to be available at high proficiency levels to parse input strings that are linearly compatible, giving rise in the case of L1 German-L2 English to non-target parses and interpretation of wh-questions.

Effects of anxiety on visuospatial pattern discrimination and decision-making processes: what can we learn from brain dynamics?

Event Abstract Back to Event Effects of anxiety on visuospatial pattern discrimination and decision-making processes: what can we learn from brain dynamics? Catherine Brandner1*, S. Tapparel1, L. Grabherr1 and Julie Palix1 1 Department of Psychology, University of Lausanne, Switzerland Detection and discrimination of visuospatial input involve at least extracting, selecting and encoding relevant information and decision-making processes allowing selecting a response. These two operations are altered, respectively, by attentional mechanisms that change discrimination capacities, and by beliefs concerning the likelihood of uncertain events. Information processing is tuned by the attentional level that acts like a filter on perception, while decision-making processes are weighed by subjective probability of risk. In addition, it has been shown that anxiety could affect the detection of unexpected events through the modification of the level of arousal. Consequently, purpose of this study concerns whether and how decision-making and brain dynamics are affected by anxiety. To investigate these questions, the performance of women with either a high (12) or a low (12) STAI-T (State-Trait Anxiety Inventory, Spielberger, 1983) was examined in a decision-making visuospatial task where subjects have to recognize a target visual pattern from non-target patterns. The target pattern was a schematic image of furniture arranged in such a way as to give the impression of a living room. Non-target patterns were created by either the compression or the dilatation of the distances between objects. Target and non-target patterns were always presented in the same configuration. Preliminary behavioral results show no group difference in reaction time. In addition, visuo-spatial abilities were analyzed trough the signal detection theory for quantifying perceptual decisions in the presence of uncertainty (Green and Swets, 1966). This theory treats detection of a stimulus as a decision-making process determined by the nature of the stimulus and cognitive factors. Astonishingly, no difference in d’ (corresponding to the distance between means of the distributions) and c (corresponds to the likelihood ratio) indexes was observed. Comparison of Event-related potentials (ERP) reveals that brain dynamics differ according to anxiety. It shows differences in component latencies, particularly a delay in anxious subjects over posterior electrode sites. However, these differences are compensated during later components by shorter latencies in anxious subjects compared to non-anxious one. These inverted effects seem indicate that the absence of difference in reaction time rely on a compensation of attentional level that tunes cortical activation in anxious subjects, but they have to hammer away to maintain performance. Conference: 10th International Conference on Cognitive Neuroscience, Bodrum, Turkey, 1 Sep - 5 Sep, 2008. Presentation Type: Poster Presentation Topic: Emotional Processing Citation: Brandner C, Tapparel S, Grabherr L and Palix J (2008). Effects of anxiety on visuospatial pattern discrimination and decision-making processes: what can we learn from brain dynamics?. Conference Abstract: 10th International Conference on Cognitive Neuroscience. doi: 10.3389/conf.neuro.09.2009.01.208 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 08 Dec 2008; Published Online: 08 Dec 2008. * Correspondence: Catherine Brandner, Department of Psychology, University of Lausanne, Lausanne, Switzerland, Catherine.Brandner@unil.ch Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Catherine Brandner S. Tapparel L. Grabherr Julie Palix Google Catherine Brandner S. Tapparel L. Grabherr Julie Palix Google Scholar Catherine Brandner S. Tapparel L. Grabherr Julie Palix PubMed Catherine Brandner S. Tapparel L. Grabherr Julie Palix Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Identification of scanned and static tactile patterns.

Most of the studies in which the interactions between target and nontarget spatial patterns have been examined have tested patterns that are generated statically. Static patterns are those in which all the elements of the pattern are presented at the same time and at a fixed location on the skin; however, most tactile information comes to the skin by means of patterns' being scanned across the surface of the skin. In the present study, the interactions between target and nontarget patterns were measured for patterns generated in both the static and the scanned modes. Nontarget patterns often interfere with the perception of target patterns. Using patterns generated in the static mode, previous studies have identified two factors that produce interference in pattern identification: response competition and masking. Masking, in turn, appears to be the result of temporal integration of the target and nontarget patterns, as well as the displacement of target features. In the present study, these factors were examined for patterns generated in both static and scanned modes. Regardless of the mode in which the patterns were generated, similar functions were obtained relating identification performance to the temporal separation between the target and the nontarget patterns. Although statically generated patterns are more easily identified than scanned patterns, particularly at brief durations, mechanisms such as response competition, temporal integration, and the displacement of target features appear to be factors that affect scanned patterns to nearly the same degree as static patterns.

Perceptual processing at adjacent locations on a single finger: masking and response competition.

When target patterns and nontarget patterns are presented either to the same or to adjacent locations on the distal pad of the index finger, the amount of interference in identifying targets depends on both the shape and the location of the nontarget (Horner, 1997). In the present study, the question of whether such interference is caused by masking (the masker in some way distorts the initial representation of the target) or by response competition (the observer mistakenly responds with the masker, rather than with the target) was investigated. A 4-to-2 paradigm was used (Craig, 1995), in which four stimuli were mapped to only two responses. Targets and nontargets were randomly selected from the set of four stimuli and presented to the same or adjacent locations on the same fingerpad. Both the distal pad and the medial pad of the index finger were tested, because innervation density varies proximodistally on the distal pad, but not on the medial pad. The results indicated that response competition was an important factor limiting perception. Furthermore, perception was affected by varying location on the distal pad, but not on the medial pad. Finally, varying location on the distal pad affected perception only when responses were based on pattern shape, not when responses were based on direction of motion. The results are discussed in terms of differences in innervation density between adjacent locations and possible resultant differences in the spatial filtering properties of the skin.

Tactile pattern perception by two fingers: temporal interference and response competition.

The identification of a spatial pattern (target) presented to one fingerpad may be interfered with by the presentation of a second pattern (nontarget) to either the same fingerpad or a second fingerpad. A portion of the interference appears to be due to masking and a portion to response competition. In the present study, vibrotactile spatial patterns were designed to extend over two fingerpads. Target and nontarget patterns were presented to the same two fingerpads with a temporal separation between the two patterns. The function relating target identification to the temporal separation between the target and nontarget was very similar to the functions obtained with one-finger patterns in temporal masking studies. Subsequent measurements showed that a substantial portion of the interference resulted from response competition. Pattern categorization was better when patterns were presented to two fingers on opposite hands than to two fingers on the same hand; however, there was more interference for patterns presented bilaterally than for patterns presented ipsilaterally. The results supported the conclusion that similar processes are involved in the perception of sequences of spatial patterns whether the patterns are presented to one or to two fingers.

Network constraints and multi-objective optimization for one-class classification

This paper introduces a constrained second-order network with a multiple objective learning algorithm that forms closed hyperellipsoidal decision boundaries for one-class classification. The network architecture has uncoupled constraints that give independent control over each decision boundary's size, shape, position, and orientation. The architecture together with the learning algorithm guarantee the formation of positive definite eigenvalues for closed hyperellipsoidal decision boundaries. The learning algorithm incorporates two criteria, one that seeks to minimize classification mapping error and another that seeks to minimize the size of the decision boundaries. We consider both additive combinations and multiplicative combinations of the individual criteria, and we present empirical evidence for selecting functional forms of the individual objectives that are bounded and normalized. The resulting multiple objective criterion allows the decision boundaries to increase or decrease in size as necessary to achieve both within-class generalization and out-of-class generalization without requiring the use of non-target patterns in the training set. The resulting network learns compact closed decision boundaries when trained with target data only. We show results of applying the network to the Iris data set (Fisher (1936), Annals of Eugenics, 7(2), 179–188). Advantages of this approach include its inherent ability for one-class generalization, freedom from characterizing the non-target class, and the ability to form closed decision boundaries for multi-modal classes that are more complex than hyperspheres without requiring inversion of large matrices.

Interference in identifying tactile patterns: response competition and temporal integration.

When two vibrotactile spatial patterns-one target and one nontarget pattern-are presented to the same location, subjects may have difficulty in identifying the target pattern. The difficulty may be in part the result of the target's and nontarget's being processed to the point of evoking competing responses. Subjects err by responding with the nontarget. Target identification may also be interfered with because the target and nontarget form a composite pattern through temporal integration, and subjects are unable to separate the features of the target and nontarget patterns. The present study addressed the issue of whether a response competition explanation of interference is consistent with the existence of temporal integration and the formation of composite patterns. A series of three experiments examined temporal integration and its relationship to response competition. The results indicate that both temporal integration and response competition can occur under similar stimulus conditions, and that both can interfere with the identification of target patterns. The results further indicate that even under conditions in which composite patterns are formed, the two patterns that constitute the composite are still identifiable. It is concluded that the interference in pattern identification attributed to response competition is not a result of temporal integration.

Vibrotactile masking: the role of response competition.

When two tactile patterns, a target and a nontarget pattern, are presented in close temporal proximity to the same location, the nontarget pattern may interfere with the identification of the target. A series of experiments examined the extent to which the interference in target identification results from masking (interference in the representation of the target at an early stage of processing) or from response competition. A response competition view of pattern perception holds that both the target and nontarget are fully processed to the level of evoking responses. Interference is produced when subjects select the nontarget rather than the target. This view was tested with a paradigm developed in studies of selective attention. Pairs of tactile patterns were presented to subjects' left index fingerpads. The amount of interference produced by a nontarget that is physically different from a target depends on whether the nontarget is associated with the same response as the target or a different response. The amount of masking also depends on the set of target and nontarget patterns that are used. The results support the conclusion that subjects have available a representation of both the target and the nontarget and that a substantial portion of the interference previously attributed to masking may be due to response competition.

The visual information processing in generating saccades through the selection of the peripheral stimulus

The purpose of this study is to examine whether the preattentive process contributes to generating saccades to the peripheral target in an unstructured background. The target and the non-target stimuli were presented simultaneously on the opposite sides at 10 deg. of eccentricity. Subjects were instructed to fixate on the target with the first saccade after the presentation of the test stimuli. The first saccade latency was measured with the EOG-technique. The target and the non-target patterns were different in textons and/or forms i.e., 1) in textons (the t-condition), 2) in forms (the f-condition), and 3) in textons and in forms (the tf-condition). While the textons are processed in th preattentive mode, the form is processed in the focal attentive mode. The mean saccade latencies in the t and the tf conditions did not differ significantly. The both were significantly shorter than those in the f condition. The number of the first error-saccades to the non-target was significantly larger in the f than the t and tf conditions. The study demonstrated that the preattentive process contributes to generating saccades to the peripheral target in an unstructured background.

Visual detectability gradients: Effect of high-speed visual experience

The detectability of a target pattern presented briefly with a number of similar nontarget patterns varies as a function of the spatial location of the target. Previous work attributes these detectability gradients to a visual search process—a non-eye movement serial scan—that examines a decaying neural representation of the image. ( Heron, 1957 Efron, Yund, & Nichols, 1987 Efron, Yund, & Nichols, 1990a Efron, Yund, & Nichols, 1990b Efron, Yund, & Nichols, 1990c Efron, Yund, & Nichols, 1990a Efron, Yund, & Nichols, 1990b Efron, Yund, & Nichols, 1990c. The results reported in the companion paper ( Ostrosky-Solis, Efron, & Yund, 1991) indicated that literacy did not affect overall performance levels but did influence scanning behavior: “… reading, or learning to read, caused the scanning mechanisms of literate subjects to adopt more consistent scan paths, from subject to subject, than they would have adopted without this reading experience.” The purpose of the present experiment was to determine the effect on this scanning mechanism, if any, of an entirely different type of visual experience —the high-speed visual processing required of tennis players. Unlike reading which requires the linguistic interpretation of a highly structured visual input, tennis skill requires rapid target detection and tracking in three-dimensional visual space as well as large scale visual-motor coordination. As in the previous experiments, subjects were required to detect a vertical stripe pattern among a number of similar non-target patterns. The experiment was performed on a group of 52 tennis players and on an age- and sex-matched group of 52 non-tennis players. The overall accuracy of target detection was greater among the tennis players than among the non-tennis players and, of more interest, there was a significant difference in the detectability gradients. The detection advantage of the tennis group seemed to reach its maximum in the first half of the scan and then to deteriorate as the scan proceeded. These results indicate that visual experience other than reading can affect the habitual activity of the scanning mechanism.

Visual detectability gradients: Effect of illiteracy

When subjects are required to detect a target pattern presented simultaneously with a number of similar non-target patterns in a brief exposure, marked differences of target detectability are observed as a function of the spatial location of the target ( Efron, Yund, & Nichols, 1987 Efron, Yund, & Nichols,1990a Efron, Yund, & Nichols, 1990b Efron, Yund, & Nichols, 1990c; Efron, Yund, & Nichols,1990a Efron, Yund, & Nichols,1990b Efron, Yund, & Nichols,1990c. These differences in detectability as a function of retinal locus, referred to collectively as a “detectability gradient,” have been attributed to a central serial processing mechanism, which scans the decaying neural representation of the image. There also is evidence suggesting that, at least in some circumstances, this gradient may be influenced by the direction in which subjects normally read ( Heron, 1957 Mishkin & Forgays, 1952 Efron et al., 1987. The object of the present experiment was to determine whether the detectability gradient obtained with the non-linguistic stimuli used in our previous experiments would differ as a function of previous reading experience. The experiment was performed on a group of 60 illiterate subjects and on a socioeconomic-matched group of 60 literate subjects. While the overall accuracy of target detection was identical in the two groups, there were significant differences between the detectability gradients of the literate and illiterate subjects. The nature of these differences indicates that reading, or learning to read, causes the scanning mechanisms of literate subjects to adopt more consistent scan paths, from subject to subject, than they would have adopted without this reading experience.

Serial processing of visual spatial patterns in a search paradigm

Previous experiments in this laboratory employing a search paradigm have found highly significant differences in the detectability of a briefly exposed target pattern as a function of the spatial location of the target when it is presented simultaneously with a number of discriminably different nontarget patterns. These detectability differences, at loci equidistant from the fovea, could not be accounted for by any known variation in retinal spatial resolution or by differential lateral masking effects of the target by nearby nontarget patterns. These observations led to the hypothesis that the target in these experiments was detected by a serial mechanism which “scanned” a persisting but rapidly degrading neural representation of the visual scene with increasing detection failures the later in time the scan processed the location occupied by the target. If this hypothesis is correct, then target detectability should vary inversely with the number of stimuli which must be examined. The present experiment confirmed this expectation. A mathematical model of such a serial scanning process also predicts other, less obvious, effects on target detectability which were observed when the number of nontarget patterns was changed.

Detectability as a function of target location: Effects of spatial configuration

Marked differences in detectability as a function of spatial location, a “detectability gradient,” are observed when subjects are required to detect a briefly exposed target pattern of uncertain location in the presence of a number of nontarget patterns. Target detectability also is inversely related to the number of nontarget patterns which are present in this search paradigm. These previous findings provide strong evidence for a serial process in which increasing probability of error occurs during a scan of a rapidly degrading neural representation of the visual image following a brief exposure to the stimuli. It is not yet established whether this scan is attentional or perceptual in nature. The present experiments test the hypothesis of an attentional scan by presenting the target and nontarget patterns in spatially segregated groups. If the scan is attentional, then target detectability under these circumstances would be expected to exhibit the characteristic phenomenon of “group processing”—a close clustering of detection performance for targets located within a group and large differences in detectability across groups. As no evidence for group processing was observed, the results fail to support the view that the scan is attentional in nature but are fully consistent with a nonattentional scan.

Target detection in one visual field in the presence or absence of stimuli in the contralateral field by right-and left-handed subjects

Marked differences in detectability are observed as a function of retinal locus when subjects are required to find a briefly exposed target pattern of uncertain location in the presence of a number of discriminably different nontarget patterns. Our previous studies using this search paradigm have attributed these detectability differences, and the right visual field detectability superiority associated with them, to a serial (scanning) mechanism which tends to examine stimuli in the right field earlier than those in the left. The present experiment, performed on large groups of right- and left-handed subjects, was designed to test the hypothesis that there are two independent serial processors, one in each hemisphere—an hypothesis which might account for the differences in detectability within and between the two half-fields in terms of hemispheric processing differences. The results are inconsistent with the dual independent serial processor hypothesis but are fully consistent with a single serial processor, a scanning mechanism, which has access to the information presented to both visual half-fields.

Detectability as a function of spatial location: Effects of selective attention

In a series of previous reports we have described differences in detectability of a target in a background of nontarget patterns as a function of its spatial location. These differences, referred to as a “detectability gradient,” have been attributed to target detection accomplished by a serial processing mechanism—a scan. The mathematical model of such a mechanism, developed in the previous report, is equally applicable to a series of attentional shifts or to a perceptual, i.e., a preattentive, mechanism. The present experiments were designed to test the hypothesis that this scan is attentional in nature. The results provide additional evidence for the scanning hypothesis but do not support the view that this scan represents a series of attentional shifts.

Detectability gradients as a function of target location

We examined the ability to detect a specified visual pattern (a target) in a randomly selected location when it was briefly presented with 11 other spatially distributed nontarget patterns and also when it was presented by itself for the same duration (50 msec) on a background of visual noise. Two experiments were designed to measure target detectability as a function of its location in the visual field where all possible target locations were equidistant from the fovea. A right visual field detection superiority was obtained in both experiments. In addition, highly significant detectability differences were observed within the right and left visual fields in both experiments. The origin of these detectability differences are interpreted in terms of parallel and serial processing mechanisms.

Transform-ratio ternary phase-amplitude filter formulation for improved correlation discrimination

A method of formulating ternary-valued (-1,0,1) correlation filters based on the ratio of spectral energies of target and nontarget patterns is proposed, and performance of such filters is investigated by computer simulations of correlation. The results confirm the intuitive expectation that such filters can enhance signalto- clutter and discrimination performance for target recognition in the presence of large amounts of input noise. These filters may be viewed as an extension of binary phase-only filters and similarly are motivated by the prospect of near-term real-time implementation.

Pattern recognition and eye-movement parameters

Pattern perception was studied by recording eye movements while Ss visually scanned nine simultaneously presented patterns of asterisks for target patterns. Pattern parameters studied were: similarity of target patterns to non-target patterns (absolute difference in the number of elements), number of target elements, and frequency of targets. Systematic correlation between the first two pattern parameters and eyemovement parameters were found. Mean duration and mean number of fixations on targets and also on non-targets increased with increased similarity. Mean duration and mean number of fixations increased on targets with an increase in the number of target elements. Non-target patterns were perceived more auicfely than targets. Fixations of longer duration were required to perceive the original target than to identify the other target patterns subsequently. The eye-movement results provide the basis for developing inferences about higher order processing of visual stimuli.