Tullis (1983, 1984) identified and quantified six conceptually distinct dimensions of alphanumeric display formats. On the basis of these dimensions, he derived regression equations which predicted performance and user perceptions in a simple search task. The current study sought to extend his findings to other common tasks performed with visually coded information--where the use of several pieces of information from predictable display locations was required. Further, complexity and visual monitoring load were manipulated to study the effects of the Tullis dimensions in a broader task context so that any boundary conditions might be identified. While there did not appear to be any clear effects of format once information was extracted from the display, the time taken to extract the information did vary with the format dimensions. Thus, their importance was not diluted by the predictability of the displays. The relative merits of alternative formats in the Scanning task, however, were not predicted successfully by the Tullis equations. This prediction failure was explained post hoc as being due to an enhancement and reversal of the effect of the Item Uncertainty dimension when display locations are known by users. Further research designed to test this hypothesis directly will be necessary to determine whether an alternative prediction system might be useful for such task situations. In contrast, the Tullis equations did predict the perceived difficulty associated with alternative formats fairly well in all task conditions. Subjects' perceptions seemed to be based largely on the ease with which information was extracted regardless of other task considerations (such as their actual level of performance). Since the regression equations were based on user perceptions of the ease of search, their predictions appear to be robust to major differences in task requirements. Finally, it was suggested that subjects' apparent inability to evaluate their performance accurately under alternative designs should serve as a warning to system designers. That is, where performance is the paramount design criterion, empirical human performance research should be conducted in the absence of a validated prediction system such as the one developed by Tullis for search.

When information is presented on a computer display in support of the human decision maker, but the amount of information is in direct proportion to computer processing powers, the human can quickly be overloaded. Because of its ability to attract and direct attention, color is one of the techniques used to enhance information display. However, the general rule that color is good for a search task, but not for strictly an identification task is limited in its applicability to complex displays: Certain design tradeoffs have to be made. Further, whether color is reported to benefit performance depends on the measure. The experiment reported here was a test of the effectiveness of color in simplifying coding, adding highlighting, and reducing clutter on an actual display, the display used in the US Army's Patriot high altitude air defense weapon system. Trained operators were tested with the existing monochrome display and an experimental color display, which was developed based on guidelines derived from the literature and on knowledge of the human/computer interface, including the operators' conceptual organization, or mental model, of the displayed information. Contrary to expectation, there was no general enhancement due to color with any of the measures taken, including the stated preference of the operators. Looking at the pattern of results over time, however, the trend was in the direction of an enhancement with color, specifically as measured by the timeliness of the engagement decision, by the pattern of activities showing the ability to use step-saving features of the system, and by subjective workload assessment. The lack of more immediate and widespread color benefits can be attributed to having to learn the color-category relationships even though early perceptual processing of color information is effortless, and to the inherent difficulty in designing a structured display to fit an unstructured task.

A review of recent research on risk perception shows that little attention has been given to risk perception for common accidents and injuries such as those that occur in and around the home. The study of common risk perception, however, could be useful in the development of psychological theories of memory and judgment, as well as in the design of better product warnings. In this study, two types of knowledge among "non-expert" individuals was tested, including knowledge about relative levels of risk and knowledge about the ways that injuries occur. Information was gathered about these two types of knowledge using (1) frequency estimation tasks in which subjects estimated annual emergency room injury frequencies for each of ten common consumer products, and (2) scenario recall tasks in which subjects recalled, generated, and organized accident scenarios for the same ten products. While performance on the frequency estimation tasks highlighted a surprising ability to assess accurately and quickly relative levels of risk, the scenario recall and rating tasks showed severe errors in judgment. In the frequency estimation task, estimates that were made within 2 seconds of category presentation were just as accurate as those made after lengthy analysis and review of scenarios. In the scenario recall task, subjects recalled or generated only about 40 percent of the common accident scenarios, and overestimated their own ability to recall scenarios. In short, information about relative levels of risk was readily accessible to individuals, while information about the ways that injuries occur often was not. A second finding concerned individuals' confidence in the relationship between estimated and actual frequencies in conditions where estimates were based on intuition (very fast estimates) or analysis (more deliberate estimates). Though frequency estimation performance did not improve after performing evaluations such as "fault tree analysis", confidence ratings nonetheless increased. This suggests that intuitive judgments can be as accurate as more thoughtful, analytical judgments and that the act of performing an analysis may sometimes lead to overconfidence in judgment. The issue of when analysis improves judgment and when it does not is worthy of further study as a general, theoretical concept.

Recent attention research indicates that attention must focus narrowly on the location of a stimulus before that stimulus can be identified. Focal attention has also been shown to play an important role in the process of localizing and integrating the basic features of stimuli. Although this suggests that little information is available without focal attention, there is picture perception research which suggests that important information is available by means of a global process that is sensitive to the meaningful relationships that exist among objects in scenes. In an attempt to reconcile this discrepancy, attention was focused on a target object while the organization of the surrounding background objects was varied. In Experiment 1, there was general interference from the presence of background objects in the visual field, but no indication that the identities or spatial organization of those objects affected performance. In Experiments 2 and 3, the objects were moved closer together to form more coherent displays. In these two experiments, there was evidence that both the identities and the spatial organization of background objects affected performance. The effects generally persisted even after attention was focused on the target. The processing of unorganized background objects was more affected by attentional manipulations than the processing of organized background objects suggesting that information in organized scenes is, at least in part, available by means of a process that is independent of focal attention.

The research constitutes an investigation of selecting material for remembering, and specifically of the ability to pick out wanted from unwanted items intermixed in the same spoken message. In Experiments 1-4, subjects tried to remember a list of words heard under (a) a no-distraction condition, in which no other words were presented; (b) a precuing condition, in which the to-be-remembered words were intermixed with unwanted words and the to-be-remembered words were specified before list presentation; and (c) a postcuing condition, which differed from the precuing condition in that the to-be-remembered words were not specified until after list presentation. Wanted and unwanted words were distinguished on the basis of semantic category (e.g., colors versus trees). In Experiments 1-3, there were 12 wanted and 12 unwanted words, and the wanted words could be recalled in any order. Recall in the precuing condition was considerably higher than in the postcuing condition and only slightly lower than in the no-distraction condition, indicating a high degree of selective remembering. Interestingly, the degree of selective remembering depended little if any on within-list positions (Experiment 1), rate of word presentation (Experiment 2), or predictability of wanted and unwanted items (Experiment 3). Such results contrast sharply with the suffix effect, in which recall of a list of items is substantially depressed by a single, nominally irrelevant item at the end of a list. Experiment 4 was similar to the first three but incorporated features of the suffix paradigm, namely a short (8-item) list and the requirement that items be recalled in their presentation order. The efficiency of selection, although reduced, was still appreciable. Experiments 5 and 6 sought to reduce the suffix effect by interpolating the suffix item after each to-be-remembered item rather than just the last one, and by presenting the list and suffix items in different voices. The suffix effect was reduced, but only modestly. It is concluded that the last item to be presented is not easily ignored, and that the suffix effect, therefore, represents a special difficulty in selective remembering.

Two prominent theories of perceptual functioning in autism were tested. WCC theory maintains that individuals with autism spectrum disorder (ASD) preferentially attend to local elements. EPF model, on the other hand, maintains that persons with ASD can attend to either the local or the global elements and that they are sensitive to small changes in environmental contingencies. Individuals with ASD and typically developing individuals (TD) performed both the selective attention task, which employed instructions about which level of the hierarchical figure to attend, and the divided attention task, which employed implicit contingencies to bias to which level of the stimulus to attend. A global advantage and global interference were found for both groups. Furthermore, ASD persons demonstrated sensitivity to the contingencies relative to TD persons. This supports the EPF model indicating that individuals with ASD perform as TD individuals for global forms but can more flexibly modify their default level of selection according to changes in environmental contingencies. / Deux théories perceptuels ont été testé. WCC clâme que les personnes qui présentent un trouble envahissant du développement (TED) montrent une inclination aux traitement locaux. EPF dit que les personnes avec TED peuvent traiter les niveau global ou local, et qu'ils sont sensibles aux petites différences dans les éventualités de l'environnement. Les personnes avec TED et le groupe de développement typique (DT) ont exécuté la tâche d'attention sélective, qui a employé des instructions duquel le niveau être présent, et la tâche d'attention divisée, qui a employé des éventualités implicites. Un avantage global et une interférence globale ont été trouvés pour les deux groupes. De plus, seulement les personnes avec TED ont démontré la sensibilité aux éventualités. Ces résultats soutiennent le compte d'EPF, et indiquent que les individus avec TED peuvent performer d'une manière caractéristique la tâche des formes globales, et peuvent modifier leur niveau implicite selon les changements subtils dans l'environnement.

Aim: Regular repeating patterns are prominent features in a visual scene. Here I consider whether regularity is an adaptable feature that produces a subsequent after-effect and whether a first- or second-order process mediates that after-effect. Method: Stimuli consisted of a 7 by 7 arrangement of elements on a baseline grid. The position of each element was randomly jittered from its baseline position by an amount that determined its degree of pattern irregularity. The elements of the pattern consisted of dark Gaussian blobs (GB), difference of Gaussians (DOG) or random binary patterns (RBP). Observers adapted for 60 seconds to a pair of patterns above and below fixation with a different degree of regularity, then adjusted the relative degree of regularity of two subsequently presented test patterns. The size of the after-effect at the point of subjective equality (PSE) was given by the baseline removed difference in regularity at the PSE or log ratio of the physical element jitter of the two test patterns at the PSE. Results: PSEs revealed that regularity is an adaptable feature that produces a unidirectional after-effect; specifically that adaptation only causes test patterns to appear less regular. The after-effect displayed transfer from GB adaptors to both DOG and RB test patterns and from DOG and (RBP) adaptors to GB patterns. Conclusion: Pattern regularity is an adaptable feature in vision, which produces a novel unidirectional after-effect I have termed Regularity After-Effect, or RAE. I propose second-order spatial-frequency channels as candidate mechanisms of regularity processing. / Objectif: Les motifs réguliers répétitifs sont des caractéristiques de premier plan dans la scène visuelle. Cette communication a comme objectif de découvrir si la régularité est une caractéristique adaptable du système visuel produisant un effet consécutif et si cet effet-consécutif est lié à un processus de premier- ou de second-ordre. Méthode: Les stimuli étaient constitués en un arrangement 7 par 7 éléments sur une grille. La position de chaque élément a été giguer au hasard à partir de sa position d'origine avec une valeur qui détermine son degré d'irrégularité. Les éléments qui constituent chaque grille pouvaient être des blobs de Gaussiennes (GB), des différence de Gaussiennes (DOG) ou de motif binaire aléatoire (RBP). Les participants ont été adaptés pour 60 secondes à une paire de motifs placée de part et d'autre d'un point de fixation ou chaque motif avait un degré différent de régularité. Les participants devaient ajuster le degré relatif de régularité de deux motifs présentés après. La taille de l'effet-consécutif est obtenue par la différence de régularité au point subjectif d'égalité soustrait à la régularité mesurée entre les deux motifs test ou par le logarithme du ratio de la différence de régularité entre les deux motifs test au point subjectif d'égalité. Résultats: Les point-subjectif d'égalité mesurée ont montrées que la régularité est une caractéristique adaptable qui produit un effet-consécutif unidirectionnel, plus précisément que les motifs sont perçus comme plus irréguliers après adaptation. On a observe un transfert à partir des stimuli d'élément GB a des motifs de test RBP et DOG et un transfert a partir des stimuli DOG et RBP vers des test de GB. Conclusion: La régularité est un élément du système visuel adaptable, produisant effet-consécutif unidirectionnel nouveau que appelé l'effet consécutif de la régularité. Je propose les canaux de fréquence-spatial de second-ordre comme mécanisme candidat au traitement de la régularité.

In everyday activity we interact with objects and need to learn how to stabilize our limbs and apply appropriate forces. During learning the central nervous system adapts to the dynamics of the limb and the environment by means of formation of an accurate internal model. In the early stages of learning in the presence of novel force fields muscle cocontraction increases. Thoroughman and Shadmehr (1999) have described cocontraction as a wasted contraction. However, Franklin et al. (2003) have shown that the increase in muscle cocontraction has an important role in learning to stabilize the limb and offset the effect of the force field when the perturbing forces cannot be accurately predicted. With practice an internal model is formed which allows the central nervous system to estimate the force to counteract the force field and therefore the muscle cocontraction level declines gradually. It has been shown that the level of muscle cocontraction remains at an asymptote after learning and the amount of cocontraction depends on the amount of required impedance to provide stability (Franklin et al., 2003; Thoroughman and Shadmehr 1999). In this study, the level of muscle cocontraction in the presence of a force field of gradually increasing strength is investigated. Subjects practiced point-to-point arm movements under a training condition where the force field strength increased gradually or under a training condition where the force field was abruptly activated and remained at its maximum strength throughout training, which served as a control. At the end of the training period both groups were performing movements at maximum force field strength. Therefore, we were able to compare the level of muscle cocontraction and performance of two groups at the same high level of force field strength. The results showed that the level of muscle cocontraction in subjects who trained with the gradually increasing force field strength was lower than the group which trained with the abrupt transition to maximum force field strength both during training and subsequently when both groups performed the task at maximum force field strength. Furthermore, based on the applied force recorded during random catch trials both groups had formed an accurate internal model at the end of learning. The observed pattern of cocontraction was consistent with the learning model proposed by Franklin et al. (2008). / Dans nos activités de tous les jours, nous interagissons avec des objets, mouvements pour lesquels nous devons apprendre à stabiliser nos membres ainsi qu'à appliquer des forces adéquates. Pendant l'apprentissage de tels mouvements, le système nerveux central s'adapte à la dynamique entre les membres et l'environnement en créant un modèle interne précis. Dans les premiers stades de l'apprentissage moteur, en présence de nouvelles forces externes, une augmentation de la cocontraction musculaire est observée. Thoroughman et Shadmehr (1999) ont décrit la cocontraction musculaire comme étant une contraction gaspillée. Par contre, Franklin et al. (2003) ont démontré que l'augmentation de la cocontraction musculaire joue un rôle important dans l'apprentissage de la stabilisation des membres, tout en déviant les effets des forces externes lorsque ces forces ne peuvent être anticipées de façon précise. Avec la pratique, un modèle interne se forme ce qui permet au système nerveux central d'estimer la force nécessaire pour contrecarrer les forces externes et donc permettre une diminution graduelle de la cocontraction musculaire. Il a été démontré que le niveau de cocontraction musculaire demeure asymptotique lorsque la période d'apprentissage est terminée. À ce moment-là, le niveau de cocontraction dépend de la quantité d'impédance nécessaire pour maintenir une certaine stabilité (Franklin et al. 2003; Thoroughman and Shadmehr 1999).Dans la présente étude, le niveau de cocontraction musculaire a été examiné lors de mouvements exécutés en présence de forces externes augmentant graduellement. Les sujets ont pratiqué des mouvements du bras d'un point à un autre selon une des deux conditions d'entraînement suivantes: 1) la force externe augmentait graduellement pendant tout l'entraînement et 2) la force externe était appliquée abruptement et demeurait à son maximum pendant tout l'entraînement, servant ainsi de condition contrôle. À la fin de la période d'entraînement, les 2 groupes de sujets ont exécuté des mouvements avec des forces externes maximales. De cette façon, nous avons pu comparer le niveau de cocontraction musculaire et la performance des 2 groupes, dans une même condition de force externe élevée. Les résultats obtenus ont montré que le niveau de cocontraction musculaire chez les sujets qui se sont entraînés avec la force externe augmentant graduellement était moins élevé que chez les sujets qui se sont entraînés avec une force augmentant abruptement à un niveau de force maximale et ce, pendant l'entraînement, de même qu'au moment de l'exécution du mouvement avec une force externe maximale. De plus, selon les forces générées par les sujets, enregistrées lors d'essais-pièges, les 2 groupes de sujets ont formé un modèle interne précis à la fin de la période d'apprentissage. Le patron de cocontraction observé était en accord avec le modèle d'apprentissage moteur proposé par Franklin et al. (2008).

Neural populations in the basolateral amygdala (BLA) have been shown to be an essential substrate for associative fear memories. However, it remains unclear whether distinct associative memories are mediated by independent or overlapping populations of BLA neurons. The focus of this dissertation is to describe efforts undertaken to use reconsolidation to advance this issue. I used the fact that initiation of reconsolidation is dependant on the reactivation of a particular memory. Therefore, if two memories are stored by the same overlapping population within the BLA, then interference through blockade of reconsolidation of one should lead to impairments in both. Conversely, if the two memories are stored independently of each other within the BLA, then blockade of reconsolidation of one memory should leave the second intact. I have investigated this with two protocols that each result in two distinct fear memories. Using a single tone-shock, I investigated the relationship of auditory and contextual fear memory. My findings demonstrate a complex functional interaction between these two memories. I designed a novel 2-tone protocol with which I attempted to use the selective blockade of reconsolidation to test a model of fear memory acquisition. This attempt illuminated the need for further knowledge regarding the boundary conditions of reconsolidation. I also describe an unbiased approach to detect molecular mechanisms unique to either consolidation or reconsolidation. One candidate from this screen was validated for its role in consolidation in the BLA. The experiments described in this dissertation provide a unique view of how fear memory representations are organized in the amygdala and how manipulations of reconsolidation can be used to understand the structure of memory. / Les populations neuronales situées dans l'amygdale basolatérale (BLA) sont reconnues comme étant un substrat essentiel aux mémoires associés à la peur. Il n'est pas encore clairement établi si des souvenirs associatifs distincts sont reliés à des populations de neurones de la BLA indépendantes ou se chevauchant. Cette dissertation décritles efforts entrepris pour faire progresser nos connaissances sur cette dernière interrogation en utilisant la reconsolidation. Pour mon étude, je me suis basé sur le fait que la reconsolidation est dépendante de la réactivation d'un souvenir en particulier. Par conséquent, si deux souvenirs sont emmagasinés par la même population de neurones se chevauchant dans la BLA, alors l'interférence causée par le blocage de la reconsolidation devrait altérer les deux souvenirs. Inversement, si deux souvenirs sont emmagasinés de manière indépendante l'un de l'autre à l'intérieur de la BLA, alors le blocage de la reconsolidation d'un seul souvenir devrait laisser le second intact. J'ai examiné cette hypothèse à l'aide de deux protocoles qui ont chacun produit deux mémoires distinctes associées à la peur. En utilisant une seule association tonalité-décharge électrique, j'ai étudié la relation entre la mémoire auditive et contextuelle associée à la peur. Mes résultats ont démontrés une interaction fonctionnelle complexe entre ces deux types de souvenirs. J'ai conçu un nouveau protocole composé de deux tonalités avec lequel j'ai essayé de bloquer sélectivement la reconsolidation pour tester un modèle d'acquisition de mémoires associées à la peur. Cette expérience démontre le besoin d'en apprendre davantage sur les conditions limitant la reconsolidation. De plus, j'ai décris une approche impartiale pour détecter les mécanismes moléculaires uniques à la consolidation ou à la reconsolidation. Suite au criblage de plusieurs molécules, une molécule candidate a été reconnue pour son rôle dans la consolidation dans la BLA. Les expériences décrites dans cette dissertation amène une perspective nouvelle sur la façon dont les mémoires reliées à la peur sont organisées dans l'amygdale et démontre comment la manipulation de la reconsolidation peut être utilisée pour comprendre la structure de la mémoire.

In virtual auditory display, sound source motion is typically cued through dynamic variations in two types of localization cues: binaural disparity cues and spectral cues. Generally, both types of cues contribute to the perception of sound source motion. For certain spatial trajectories, however, namely those lying on the surfaces of cones of confusion, binaural disparity cues are constant, and motion must be inferred solely on the basis of spectral cue variation. This thesis tests the effectiveness of these spectral variation cues in eliciting motion percepts. A virtual sound source was synthesized that traversed sections of a cone of confusion on a particular sagittal plane. The spatial extent of the source's trajectory was systematically varied to probe directional discrimination thresholds. / Dans le domaine de la spatialisation, le mouvement de la source sonore est généralement indiqué par des variations dynamiques selon deux types d'indices de localisation : des indices de disparite binaurale et des indices spectraux. En régle rénérale, les deux types d'indices contribuent à la perception du mouvement de la source sonore. Cela dit, dans le cas de certaines trajectoires spatiales, à savoir celles qui reposent sur la surface des cônes de confusion, les indices de disparité binaurale sont constants et le mouvement ne s'induit forcément qu'à partir des variations spectrales. La présente thése sonde l'efficacité de ces indices de variation spectrale en indiquant les perceptions du mouvement. Une source sonore virtuelle a été synthétisée et chemine sur la surface d'un cône de confusion sur un plan sagittal déterminé. L'étendue spatiale de la trajectoire de la source a été ajustée systématiquement afin de sonder les seuils critiques de discrimination de mobilité directionnelle.