Metamemory accuracy: effects of feedback and the stability of individual differences.

This study addressed two questions about metamemory accuracy: how feedback about recall performance affects confidence-recall accuracy and whether individual differences in confidence-recall accuracy are stable across different sets of test items. College students answered general knowledge questions and made confidence ratings about the correctness of the answers. Half the students were told whether their answers were correct. All students answered half the questions a second time. The results show that feedback did not produce a general improvement in metamemory accuracy; the improvement was specific to the questions for which feedback was provided. Also, individual students' metamemory accuracy showed moderate alternate-forms stability when each test was made up of 250 items. Therefore, researchers studying individual differences in metamemory accuracy on recall tasks should use tests that yield several hundred responses.

Instability of individual differences in the association between confidence judgments and memory performance.

There are large individual differences in the degree of association between the accuracy of memories and subjective confidence in those memories. Are these differences stable within the same test, and between alternate forms of a test? In Experiment 1, college students were tested on 3 recognition memory tasks, then retested 2 weeks later on alternate forms of the same tasks. The relationship between confidence judgments and recognition performance displayed low split-half stability and low alternate-forms stability. A second experiment with elderly adults replicated these findings. In a third experiment, college students recalled answers to general knowledge questions and rated confidence in the correctness of each answer. Individual differences in the association between confidence and recall performance were not stable across the odd- and even-numbered items on the test. These data indicate the need for the development of procedures that will produce stable estimates of individuals' metacognitive accuracy.

Design and synthesis of piperidine-3-carboxamides as human platelet aggregation inhibitors.

A detailed structure-activity analysis was carried out using eight 1-alkyl(aralkyl)nipecotamides (type 5), 33 bis-nipecotamidoalkanes and aralkanes (type 6), and 7 N,N'-bis(nipecotoyl)-piperazines (type 7) as inhibitors of human platelet aggregation. Steric factors played an important role in determining the activity of type 5 compounds possessing an an appropriate degree of hydrophobic character. Types 6 and 7 compounds were more potent than the corresponding type 5 molecules. Hydrophobic character appeared to influence the activity of type 6 compounds. A 3-substituent on the piperidine ring was necessary for antiplatelet activity; the substituent should be preferably an amide with its C attached directly to the ring. 3,5-Disubstitution and 2-substitution led to a decline in activity. Optimal activity was attained when the two nipecotoyl ring N atoms were connected by an aralkyl group, and separated by approximately 7 A. It is suggested that van der Waals forces and pi interactions may govern the inhibitor-platelet interaction. The most potent type 6 inhibitor was alpha,alpha'-bis[3-(N-ethyl-N-butylcarbamoyl)piperidino]-p-xylene (6i). The most potent type 5 compound was 1-decyl-3-(N,N-diethylcarbamoyl)piperidine (5a). Any substitution on the piperazine ring of type 7 compounds led to a decline in activity, the most active analog being N,N'-bis(1-decylnipecotoyl)piperazine (7a). It is suggested that nipecotamides interact with anionic platelet sites located 7 A from each other and connected by a hydrophobic well.

Structure-from-motion based on information at surface boundaries.

Existing computational models of structure-from-motion--the appearance of three-dimensional motion generated by moving two-dimensional patterns--are all based on variations of optical flow or feature point correspondence within the interior of single objects. Three separate phenomena provide strong evidence that in human vision, structure-from-motion is significantly affected by surface boundary cues. In the first, a rotating cylinder is seen, though no variation in optical flow exists across the apparent cylinder. In the second, the shape of the bounding contour of a moving pattern dominates the actual differential motion within the pattern. In the third, the appearance of independently moving objects changes significantly when the boundary between them becomes indistinct. We describe a simple computational model sufficient to account for these effects. The model is based on qualitative constraints relating possible object motions to patterns of flow, together with an understanding of the patterns of flow that can be discriminated in practice.

Structure-from-motion by tracking occlusion boundaries.

Active visual tracking of points on occlusion boundaries can simplify certain computations involved in determining scene structure and dynamics based on visual motion. Tracking is particularly effective at surface boundaries where large, discontinuous changes in depth are occurring. Two such techniques are described here. The first provides a measure of ordinal depth by distinguishing between occluding and occluded surfaces at a surface boundary. The second can be used to determine the direction of observer motion through a scene.

Postoperative radiation of open head and neck wounds.

Complication rates are lower using postoperative radiation therapy and cure rates at least compatible to preoperative radiation therapy. However, one of the concerns with postoperative radiation treatment is the possibility of delay in beginning the treatment because of an unhealed surgical wound. A delay of more than 6 weeks is detrimental. In order to study the effect of radiation therapy on incompletely healed wounds, a retrospective chart review of such cases during the period 1977 to 1984 was undertaken. One hundred and eighty-five patients had planned postoperative radiation therapy, and 13 of these began radiation therapy with an unhealed wound or fistula. Six of 10 wounds closed spontaneously, 4 required surgical closure, and 3 failed to heal. Seven patients in this study died with cancer, 2 died of other causes, 3 are alive without disease, and 1 patient remains alive with disease. We conclude that giving radiation therapy to an open wound with appropriate precaution can be done without serious complications.

Optical flow estimation: an error analysis of gradient-based methods with local optimization.

Multiple views of a scene can provide important information about the structure and dynamic behavior of three-dimensional objects. Many of the methods that recover this information require the determination of optical flow-the velocity, on the image, of visible points on object surfaces. An important class of techniques for estimating optical flow depend on the relationship between the gradients of image brightness. While gradient-based methods have been widely studied, little attention has been paid to accuracy and reliability of the approach. Gradient-based methods are sensitive to conditions commonly encountered in real imagery. Highly textured surfaces, large areas of constant brightness, motion boundaries, and depth discontinuities can all be troublesome for gradient-based methods. Fortunately, these problematic areas are usually localized can be identified in the image. In this paper we examine the sources of errors for gradient-based techniques that locally solve for optical flow. These methods assume that optical flow is constant in a small neighborhood. The consequence of violating in this assumption is examined. The causes of measurement errors and the determinants of the conditioning of the solution system are also considered. By understanding how errors arise, we are able to define the inherent limitations of the technique, obtain estimates of the accuracy of computed values, enhance the performance of the technique, and demonstrate the informative value of some types of error.

Analysis of accretion and deletion at boundaries in dynamic scenes.

In dynamic scenes, the presence of object boundaries is often signaled by the appearance or disappearance of occluded surfaces over time. Such regions of surface accretion or deletion can be found using matching techniques similar to those used to determine optical flow in an image sequence. Regions in one frame that are not adequately matched by any region in previous frames correspond to accretion. Regions that have no matches in subsequent frames correspond to deletion. In either case, an occlusion boundary is present. Furthermore, by associating accretion or deletion regions with a surface on one side of a boundary, it is possible to determine which side of the boundary is being occluded. This association can be based purely on visual motion-the accretion or deletion region moves with the same image velocity as the remaining visible surface to which it is attached.

Dynamic occlusion analysis in optical flow fields.

Optical flow can be used to locate dynamic occlusion boundaries in an image sequence. We derive an edge detection algorithm sensitive to changes in flow fields likely to be associated with occlusion. The algorithm is patterned after the Marr-Hildreth zero-crossing detectors currently used to locate boundaries in scalar fields. Zero-crossing detectors are extended to identify changes in direction and/or magnitude in a vector-valued flow field. As a result, the detector works for flow boundaries generated due to the relative motion of two overlapping surfaces, as well as the simpler case of motion parallax due to a sensor moving through an otherwise stationary environment. We then show how the approach can be extended to identify which side of a dynamic occlusion boundary corresponds to the occluding surface. The fundamental principal involved is that at an occlusion boundary, the image of the surface boundary moves with the image of the occluding surface. Such information is important in interpreting dynamic scenes. Results are demonstrated on optical flow fields automatically computed from real image sequences.

Recognition of moving objects using feature signatures.

An important application of machine vision systems is the recognition of known three-dimensional objects. A major difficulty arises when two or more objects project the same or similar two-dimensional image, often resulting in misclassification and degradation of system performance. The changes in images which result from the motion of objects provide a source of three-dimensional information which can greatly aid the classification process, but this three-dimensional analysis is computationally complex and subject to many sources of error. This work develops a methodology which utilizes the information derived from the apparent changes in object features over time to facilitate the recognition task, without the need to actually recover the three-dimensional structure of the objects under view. The basic approach is to generate a ``feature signature'' by combining the feature measurements of the individual regions in a long sequence of images. The static information in the individual frames is analyzed along with the temporal information from the entire sequence. These techniques are particularly applicable in situations where static image processing methods cannot discriminate between ambiguous objects. Two example implementations are presented to illustrate the application of the techniques of object recognition using motion information.

Face memory and hemispheric preference: emotionality and extraversion.

Subjects made arousing or nonarousing judgments about photographs of strangers, then had an unannounced recognition test over the photographs. Emotional orienting tasks led to better retention than nonemotional tasks. Assuming emotionality is predominantly a right-hemisphere activity, then this result is consistent with other research showing a right-hemisphere advantage in processing faces. This difference was most clear for subjects with a right-hemisphere cognitive style. Extraversion had no effect on face recognition, nor did a subject's cognitive style seem to be associated with extraversion or neuroticism scores.

Distribution of histidine-rich basic protein, a possible keratin matrix protein, in rat oral epithelium.

The indirect fluorescent-antibody technique was used to locate histidine-rich basic protein, filaggrin. In the newborn, immunofluorescence was seen in the cornified layers and in keratohyalin granules throughout the mouth using antibody specific for epidermal filaggrin, a distribution similar to that in epidermis where it is thought that filaggrin functions as the keratin matrix protein. In the adult immunofluorescence was in keratohyalin granules of palate, buccal and tongue epithelium but in the stratum corneum was limited to the soft palate with weak, patchy areas in the densely keratinized epithelium of the hard palate and tongue. Immunofluorescence was delineated at the boundary between the soft and hard palates. A protein apparently identical to epidermal filaggrin was identified in extracts of newborn palate by its mobility on sodium dodecyl sulphate-polyacrylamide gels and subsequent reaction with the antibody used for immunofluorescent studies. This protein was not detected in extracts of adult oral epithelia. Both newborn and adult tissues contained high mol. wt cross-reactive protein, suggestive of the filaggrin-precursor protein extractable from keratohyalin granules. The distribution of filaggrin was consistent with its function as a keratin matrix protein in the newborn oral epithelium and some less densely keratinized regions of the adult. However, in the adult mouth, filaggrin is not detectable in the stratum corneum of the most densely keratinized regions. Thus, the protein must be lost or its antigenic sites altered with maturation of the animal, depending on the type and extent of keratinization.

Disparity analysis of images.

An algorithm for matching images of real world scenes is presented. The matching is a specification of the geometrical disparity between the images and may be used to partially reconstruct the three-dimensional structure of the scene. Sets of candidate matching points are selected independently in each image. These points are the locations of small, distinct features which are likely to be detectable in both images. An initial network of possible matches between the two sets of candidates is constructed. Each possible match specifies a possible disparity of a candidate point in a selected reference image. An initial estimate of the probability of each possible disparity is made, based on the similarity of subimages surrounding the points. These estimates are iteratively improved by a relaxation labeling technique making use of the local continuity property of disparity that is a consequence of the continuity of real world surfaces. The algorithm is effective for binocular parallax, motion parallax, and object motion. It quickly converges to good estimates of disparity, which reflect the spatial organization of the scene.

Automated computer screening of chest radiographs for pneumoconiosis.

The results of two complementary approaches for performing diagnostic screening for the presence of coal workers' pneumoconiosis (CWP) from the routine posterior-anterior chest radiograph are presented. The first is a digital approach utilizing the measurement of image texture, while the second uses hybrid optical-digital methods involving the optical Fourier transform. Both approaches yield classification results comparable to experienced radiologists.