INTRODUCTION: Reaction time may be broadly defined as the time between stimulus presentation and a response. Analysis of reaction time in terms of rate of force development (RFD), peak force, and surface electromyography (EMG) may help bridge the gaps in knowledge pertaining to the neuromuscular system's role in reaction time. The purpose of the present study was to identify predictors of reaction time using digital hand grip dynamometry and EMG. It was hypothesized that RFD and rate of EMG rise (RER) at the onset of a contraction would correlate with reaction time. METHODS: For grip testing, participants were instructed to squeeze a handheld dynamometer with the right hand "…as hard and fast as possible" for 5 seconds upon hearing a "beep" from the computer. A total of 5 attempts were performed, with 1-minute rest periods. Bipolar surface EMG signals were detected from the right first dorsal interosseous (FDI) and flexor carpi radialis (FCR) muscles throughout grip testing. Bivariate correlations (Pearson r) were used to examine the statistical associations. The 95% confidence interval (CI) for each Pearson r was also computed. An alpha level of p ≤ 0.05 was used to reject the null hypothesis. RESULTS: Significant correlations were observed between reaction time and all other measures of grip force (r = -0.507 to -0.557, p= 0.016 to 0.042), except for time until peak force (r = 0.029, p = 0.915). As FDI EMG amplitude increased reaction time decreased (r = -0.664, p = .005). CONCLUSION: Many of the grip force variables were significantly associated with reaction time. Peak force and rapid force variables showed significant correlations with reaction time. While no significant correlations for any of the FDI RER or FCR variables were found, EMG amplitude from the FDI presented the strongest bivariate correlation. As FDI EMG amplitude, peak force, and rapid force variables increased reaction time decreased. These findings give some insight into the neuromuscular system's role in hand grip tasks and help broaden the current understanding of variables that may be used to assess or improve reaction time in the clinical setting.

This study investigated distortion that occurs when raw scores are converted to ipsative scores on Affinity 2.0, a relatively new instrument for assessing sexual interest. Using a sample of 146 non-offending, heterosexual females, this study examined the characteristics of distorted ipsative score profiles and attempted to develop an algorithm to identify such distortions. A method was developed for defining distortion objectively. Of the 146 profiles,125 were found to contain some degree of distortion. Several hypotheses were formulated as to variables that might be related to distortion. These relationships were examined using Pearson Product Moment Correlations. Several statistically significant, but weak, correlations were found. An interaction effect was calculated for four of these variables, and was found to have a moderately strong correlation with distortion (r = .530, p <.01). An algorithm for identifying distortion was developed using this interaction effect. Several cut-off scores were tested. The most effective cut-off only correctly identified 42.9% of the significantly distorted profiles. Implications and limitations of the results are discussed, and directions for future research are provided.

The experiments reported within this thesis use psychophysical techniques to examine the factors which determine perceived multisensory timing in humans. Chapters 1 and 2 describe anatomical and psychophysical features of temporal processing, respectively, whilst Chapter 3 introduces the reader to psychophysical methods. Chapter 4 examines the relationship between two measures of sensory latency, reaction time (RT) and crossmodal temporal order judgment (TOJ). Despite task and attentional manipulations the two measures do not correlate, suggesting that they measure some fundamentally different aspect(s) of temporal perception. Chapter 5 examines the effects of adaptation to asynchronous stimulus pairs on perceived audiovisual (AV), audiotactile (AT) and visuotactile (VT) temporal order. Significant temporal shifts are recorded in all three conditions. Evidence is also presented showing that crossmodal TOJs are intransitive. Chapter 6 shows that concurrent adaptation to two sets of asynchronous AV stimulus pairs causes perceived AV temporal order to recalibrate at two locations simultaneously, and that AV asynchrony adaptation effects are significantly affected by observers¿ attention during adaptation. Finally, Chapter 7 shows that when observers are accustomed to a physical delay between motor actions and sensory events, an event presented at a reduced delay appears to precede the causative motor action. The data are well-described by a simple model based on a strong prior assumption of physical synchrony between motor actions and their sensory consequences.

The current study aimed to investigate the effects of disfluencies, specifically filled pauses (FP) and unfilled pauses (UP), on reaction time (RT) to target words and hyponyms of target hypernyms(targets = target words + hyponyms of target hypernyms). Two experiments were conducted, withthe first experiment examining the impact of disfluencies on RTs to target words in utterances, whilethe second experiment explored their effect on hyponyms of target hypernyms. The experiments wereconducted on six participants, comprising two females and four males, following a within-subjectdesign.Unlike previous studies that have examined disfluencies in the Swedish language, this study dis-tinguished between two categories of filled pauses, namely ehm (E:m, @:m, œ:m, or æ:m) and öh (E:,@:, œ:, or æ:). However, the results revealed that this distinction had no significant effect on RTs.Conversely, a significant difference in RTs was observed between genders, with women exhibitingfaster reaction times compared to men. Participants generally reacted more swiftly to target wordsthan to hyponyms of target hypernyms.Interestingly, filled pauses were found to reduce reaction times to target hypernyms compared tounfilled pauses. However, they did not demonstrate a similar effect on reaction times to target words.Caution should be exercised in interpreting these results due to the limited sample size. Nevertheless,these findings have intriguing implications for the entropy hypothesis (EH) and attention-heighteninghypothesis (AHH) concerning filled pause production.

The approach-avoidance task (AAT) is an implicit task that measures people’s behavioral tendencies to approach or avoid stimuli in the environment. In recent years, it has been used successfully to help explain a variety of health problems (e.g., addictions and phobias). Unfortunately, more recent AAT studies have failed to replicate earlier promising findings. One explanation for these replication failures could be that the AAT does not reliably measure approach-avoidance tendencies. Here, we first review existing literature on the reliability of various versions of the AAT. Next, we examine the AAT’s reliability in a large and diverse sample (N = 1077; 248 of whom completed all sessions). Using a smartphone-based, mobile AAT, we measured participants’ approach-avoidance tendencies eight times over a period of seven months (one measurement per month) in two distinct stimulus sets (happy/sad expressions and disgusting/neutral stimuli). The mobile AAT’s split-half reliability was adequate for face stimuli (r = .85), but low for disgust stimuli (r = .72). Its test–retest reliability based on a single measurement was poor for either stimulus set (all ICC1s < .3). Its test–retest reliability based on the average of all eight measurements was moderately good for face stimuli (ICCk = .73), but low for disgust stimuli (ICCk = .5). Results suggest that single-measurement AATs could be influenced by unexplained temporal fluctuations of approach-avoidance tendencies. These fluctuations could be examined in future studies. Until then, this work suggests that future research using the AAT should rely on multiple rather than single measurements.

No description available.

Collision avoidance systems (CASs) are being developed and fielded to reduce the number and severity of rear-end crashes. Kinematic algorithms within CASs evaluate sensor input and apply assumptions describing human-response timing and deceleration to determine when an alert should be presented. This dissertation presents an analytic assessment of dynamic function and performance CASs and associated driver performance for preventing automotive rear-end crashes. A method for using naturalistic data in the evaluation of CAS algorithms is described and applied to three algorithms. Time-series parametric data collected during 13 rear-end crashes and 70 near-crashes are input into models of collision avoidance algorithms to determine when the alerts would have occurred. Algorithm performance is measured by estimating how much of the driving population would be able to respond in the time available between when an alert would occur and when braking was needed. A sensitivity analysis was performed to consider the effect of alternative inputs into the assessment method. The algorithms were found to warn in sufficient time to permit 50–70% of the population to avoid collision in similar scenarios. However, the accuracy of this estimate was limited because the tested algorithms were found to alert too frequently to be feasible. The response of the assessment method was most sensitive to differences in assumed response-time distributions and assumed driver braking levels. Low-speed crashes were not addressed by two of the algorithms. Analysis of the events revealed that the necessary avoidance deceleration based on kinematics was generally less than 2 s in duration. At the time of driver response, the time remaining to avoid collision using a 0.5g average deceleration ranged from â 1.1 s to 2.1 s. In 10 of 13 crashes, no driver response deceleration was present. Mean deceleration for the 70 near-crashes was 0.37g and maximum was 0.72g. A set of the events was developed to measure driver response time. The mean driver response time was 0.7 s to begin braking and 1.1 s to reach maximum deceleration. Implications for collision countermeasures are considered, response-time results are compared to previous distributions and future work is discussed. / Ph. D.

No / Language is more than a source of information for accessing higher-order conceptual knowledge. Indeed, language may determine how people perceive and interpret visual stimuli. Visual processing in linguistic contexts, for instance, mirrors language processing and happens incrementally, rather than through variously-oriented fixations over a particular scene. The consequences of this atypical visual processing are yet to be determined. Here, we investigated the integration of visual and linguistic input during a reasoning task. Participants listened to sentences containing conjunctions or disjunctions (Nancy examined an ant and/or a cloud) and looked at visual scenes containing two pictures that either matched or mismatched the nouns. Degree of match between nouns and pictures (referential anchoring) and between their expected and actual spatial positions (spatial anchoring) affected fixations as well as judgments. We conclude that language induces incremental processing of visual scenes, which in turn becomes susceptible to reasoning errors during the language-meaning verification process.

Context: It has been suggested that muscle fatigue can lead to injury, however, research investigating this phenomenon in functional ankle instability (FAI) subjects is lacking. Aim: The purpose of this thesis was to research postural sway and muscular latency in FAI subjects and healthy controls, both before and immediately after localised and globalised fatigue protocols. Subjects: All subjects used in this project were males, between the ages of 18 and 25 years, and participated in regular (&gt;2 x week) aerobic exercise. Subjects were categorised into healthy subjects, or subjects with a history of FAI using the FAI questionnaire. Methods: Neuromuscular control was analysed in FAI subjects and healthy controls through measures of muscular latency and postural sway. These measures were repeated both before and immediately after localised and globalised fatigue protocols. Results: The induction of localised and globalised fatigue had no effect on muscle latency in the FAI or healthy subjects. However, postural sway was significantly increased in the FAI subjects, following localised and globalised fatigue, with globalised fatigue also significantly increasing postural sway in the healthy subjects. The globalised football-specific fatigue protocol caused the greatest deficits in the FAI subjects, but also the healthy controls. Conclusions: In terms of muscle latency individuals that participate in sports, as well as sports clinicians and coaches, should not be concerned about the theorised relationship between the onset of fatigue and an increased injury risk at the ankle. However, in terms of postural sway the globalised football-specific fatigue protocol caused the greatest deficits. This highlights that the fatigued individual may be at greater risk of musculoskeletal injury during prolonged exercise that involves multiple joints, such as a football match.

L’objectif de ce projet de recherche était de vérifier la présence de changements de sensibilité de la rétine et du système circadien suite à deux semaines d'exposition à un milieu faiblement ou fortement éclairé, dans des conditions contrôlées en laboratoire. De plus, comme un changement de sensibilité peut modifier l'ajustement du système circadien au cycle jour-nuit extérieur, nous voulions également vérifier si la phase circadienne serait modifiée par le traitement et si la vigilance et l’humeur seraient affectées. Dix sujets ont été exposés à de la lumière tamisée (70 lux [LT]) et 10 ont été exposés à de la lumière vive (3000 lux [LV]) pendant 12 jours consécutifs en laboratoire de 8h45 à 19h00 tous les jours. L’exposition à la lumière a été mesurée 5 jours avant l’entrée au laboratoire dans l’habitat naturel du sujet et pendant la période en laboratoire à l’aide de l’Actiwatch-L®. La sensibilité rétinienne a été mesurée avant et après le traitement lumineux, par un électrorétinogramme (ERG) et la sensibilité circadienne, par le test de suppression de mélatonine salivaire. Tout au long du protocole, la vigilance, la somnolence et l'humeur ont été évaluées à plusieurs moments de la journée à intervalles prédéterminés. Après 12 jours d’exposition en lumière contrôlée, l’amplitude de l’onde-a au Vmax à l’ERG photopique a diminué en LV alors qu’elle a augmenté en LT. À l’ERG scotopique, une différence de sensibilité rétinienne (log K) entre les groupes avant le traitement expérimental s’est amenuisée à la fin du traitement (p=.053). La suppression de mélatonine après 90 minutes d’exposition au test de suppression a diminué en LV alors qu’il n’y a pas eu de modification en LT, cependant cette interaction n’était pas significative (p=.16). La phase circadienne des sujets exposés à LV a été devancée de 58 minutes (p=.04) alors qu’elle a été retardée de 26 minutes en LT (p=.32). Les mesures de vigilance subjective (EVA) ont indiqué que les sujets LV se considéraient plus éveillés que les sujets LT après le traitement (p=.02). Par contre, aucune différence n’est apparue quant aux mesures de performance psychomotrice ni de l’humeur. L’histoire lumineuse n’a pas modifié la sensibilité rétinienne dans le sens prévu par les hypothèses alors qu’il y a eu une tendance vers une augmentation de la sensibilité circadienne en condition de lumière tamisée. L’amélioration de la vigilance subjective après l’exposition en LV n’a pas été soutenue par les résultats de la performance psychomotrice. L’histoire lumineuse n’a eu aucun effet sur l’humeur des sujets. Cette étude souligne l’importance d’utiliser des mesures permettant de départager les effets immédiats d’un traitement lumineux des effets à long terme autant sur le plan rétinien que circadien. Il reste également complexe d’étudier en laboratoire des changements adaptatifs qui se produisent dans le milieu naturel en raison du confinement et des modifications physiologiques et psychologiques pouvant y être associées. / The purpose of this study was to evaluate the impact of two weeks exposure in a dim or bright light environment on retinal and circadian sensitivity to light in a controlled laboratory setting. Given that a change in sensitivity to light could modify the circadian adjustment to the external light-dark cycle, it was expected that the circadian phase would be modified with the light treatment and have an effect on alertness and mood. Ten participants were exposed to a dim light (DL) environment (70 lux) and 10 participants to a bright light (BL) environment (3000 lux) 10 hours per day for 12 consecutive days. Light exposure was measured 5 days prior to the onset of the experiment in the subject’s natural environment and during the entire laboratory experiment with an Actiwatch-L®. Retinal function was assessed with the electroretinogram (ERG). Circadian light sensitivity was evaluated with a salivary melatonin suppression test. Retinal and circadian sensitivity measures were taken before and after the experimental condition. Alertness, sleepiness and mood were measured several times per day at fixed intervals. After 12 days of controlled light exposure, the amplitude of amax of the photopic ERG was decreased in BL whereas it was increased in DL. In scotopic ERG, there was a difference in the retinal sensitivity (log K) between the two groups before light treatment that disappeared at the end of light exposure (p=.053). The percentage of melatonin suppression after 90 minutes exposure to the melatonin suppression test was decreased in BL while it did not changed in DL condition. This interaction, however, did not reach significance (p=.16). We measured a 58 minutes phase advance in the BL condition (p=.04) and a 26 minutes phase delay in DL (p=.32). Measures of subjective vigilance (EVA) suggested that BL subjects were more alert after the light treatment than DL subject (p=.02). However, there was no difference in the psychomotor vigilance task or mood. Light history did not modify the retinal sensitivity as predicted by the hypotheses. However, there was a trend toward an increased circadian sensitivity in the dim light condition. The improvement of subjective vigilance in the BL condition was not supported by the results at the psychomotor vigilance task. Light history had no effect on the mood of the subjects. Long-term effects of a light treatment are difficult to isolate from shorter direct effects of light. Moreover, the study of adaptative environmental changes that spontaneously appeared in the field are possibly masked in a laboratory setting where confinement could induce physiological and psychological changes.