Attentional control during visual search: The effect of irrelevant singletons

Four experiments investigated whether a highly salient color singleton can be ignored during serial search. Observers searched for a target letter among nontarget letters and were instructed to ignore an irrelevant, highly salient color singleton that was either compatible or incompatible with the response to the target letter. The results...

Detection of adulteration in orange juices by a new screening method using proton NMR spectroscopy in combination with pattern recognition techniques

This paper describes the application of proton NMR spectroscopy as a screening tool for the determination of the authenticity of orange juices. Principal component and discriminant analyses were used to discriminate between authentic and nonauthentic (suspect) samples. In one set of profiles, additions of sucrose, beet medium invert sugar,...

A puzzling percept of stimulus stabilization

A visual illusion is reported which comprises the following: when a monitor with a moving constant velocity grating is swayed in front of a subject, the grating may be perceived as freezing or decelerating on the screen. This percept appears to depend on the magnitude and direction of the retinal grating velocity, relative to that of the moni...

Partial linear fit: A new NMR spectroscopy preprocessing tool for pattern recognition applications

NMR spectroscopy is increasingly used in combination with multivariate analysis applications. Especially in the analysis of food products and the study of natural processes it has proved its usefulness. The samples used in these evaluations are however, often difficult to control. 'Positional' shifts of peaks due to differences in pH and other...

Determination of ocular torsion by means of automatic pattern recognition

A new, automatic method for determination of human ocular torsion (OT) was devel-oped based on the tracking of iris patterns in digitized video images. Instead of quanti-fying OT by means of cross-correlation of circular iris samples, a procedure commonly applied, this new method automatically selects and recovers a set of 36 significant...

Knowledge-based segmentation for automatic Map interpretation

In this paper, a knowledge-based framework for the top-down interpretation and segmentation of maps is presented. The interpretation is based on a priori knowledge about map objects, their mutual spatial relationships and potential segmentation problems. To reduce computational costs, a global segmentation is used when possible, but an...

Evaluation of infrared signature suppression of ships

Reduction of the infrared signature of warships helps to increase their survivability. Two methods to reduce the infrared signature are discussed: the cooling of exhaust gases and the application of low emissivity paint. The infrared signature of a generic frigate has been calculated with and without signature reduction. The signature values are...

The relationship between event-related brain potential, heart rate, and blood pressure responses in an S1-S2 paradigm

Event-related brain potential (ERP), heart rate (HR), and blood pressure (BP) responses were examined during the 6s foreperiod of a choice-reaction task. Low and high trait-anxious males were required to make same/different judgements based on the similarity of two successively presented visual patterns. The pitch of a warning tone, presented at...

Atmospheric effects on FPAs in IRSTs

In 1993 and 1994 TNO-FEL participated in the execution of experiments over the North Sea in order to derive the infrared atmospheric scintillation and beam deformation process. In 1993 the NATO MAPTIP trial allowed us to observe an infrared point source from a platform at sea with a 10 micron FLIR, at various ranges (0.5 - 5 NM) and in various...

IRST and its Perspective

This paper starts with a review of the status of presently available IRST sensors and continues with the problems that they are facing, even after more than 25 years of development. The problems arise from uncertainty in target signatures, atmospheric effects, background clutter and different types of hardware and processing shortcomings. Yet...

Parallel search for a conjunction of contrast polarity and shape

When a target object embedded in an array of other objects can be distinguished along a single feature dimension (e.g., colour or shape), it can be detected in parallel. When a target object is defined by a conjunction of stimulus features, search has to be conducted serially, indicating that the visual system is incapable of conducting a...

Perceptual selectivity for color and form

Three visual-search experiments tested whether the preattentive parallel stage can selectively guide the attentive stage to a particular known-to-be-relevant target feature. Subjects searched multielement displays for a salient green circle that had a unique form when surrounded by green nontarget squares or had a unique color when surrounded by...

Exogenous and endogenous control of attention: The effect of visual onsets and offsets

Two experiments were carried out to investigate the relation between exogenous and endogenous control of visual attention. Subjects searched for a target letter among three nontarget letters that were positioned on an imaginary circle around a fixation point. At different cue-display intervals, a centrally located arrowhead cue reliably...

Cross-dimensional perceptual selectivity

Three visual search experiments tested whether top-down selectivity toward particular stimulus dimensions is possible during preattentive parallel search. Subjects viewed multielement displays in which two salient items, each unique in a different dimension—that is, color and intensity (Experiment 1) or color and form (Experiments 2 and 3)—were...

Categorization and identification of simultaneous targets

Early and late selection theories of visual attention disagree about whether identification occurs before or after selection. Studies showing the category effect, i.e., the time to detect a letter is hardly affected by the number of digits present in the display, are taken as evidence for late selection theories since these studies suggest...

Vervormde textstrings herkennen met een spatio-temporeel patroon herkennings (SPR) neuraal netwerk

FEL heeft een SPR (Spatio-temporeel Pattern Recognition) neuraal nerwerk geïmplementeerd om vervormde woorden en/of delen van zinnen, in dit geval de namen van schepen, te herkennen in een real-time toepassing. Deze namen kunnen vervormd worden door transmissie en/of type fouten. SPR legt de nadruk op de volgorde van de karakters in een woord....

Effects of location and form cueing on the allocation of attention in the visual field

Two experiments were conducted which tested the effect of two different types of cues on the allocation of attention in the visual field. Subjects responded to a target appearing either 6.5° to the right or to the left of fixation in a field with small randomly positioned line segments. The target form was either a circle or diamond in which a...

Slow cortical and heart rate correlates of discrimination performance

Slow EEG potentials (Fz, Cz, Pz) and heart rate were recorded during the foreperiod of a reaction task, which involved different levels of discrimination difficulty. A simple reaction task was compared with a selective reaction task where either an easy or a difficult discrimination was required. In general, the terminal amplitude of the CNV was...