Thesis (M.A.)--University of British Columbia, 2003. / Includes bibliographical references (leaves 154-170).

Traditional psychophysical studies have been primarily unimodal experiments due to the ease in which a single sense can be isolated in a laboratory setting. This study, however, presents participants with auditory and visual stimuli to better understand the interaction of the two senses in visuospatial perception. Visual stimuli, presented as Gaussian distributed blobs, moved laterally across a computer monitor to a central location and "bounced" back to their starting position. During this passage across the screen, a brief auditory "click" was presented via headphones. Participants were asked to respond to the bounce of the ball, and response latency was recorded. Response latency to the bounce position varied as a function of baseline (no sound) and the varying sound offset locations.

Thesis is focusing on influence of caffeine on the change of reaction time of individual. The theoretical part consists of the introduction of the specific subject and is following by information about positive and negative caffeine effect on the human body. Certain part of dissertation presents some liquid food products, where caffeine is included. The description of the reaction time of the individual before and after consumption is mentioned as well. The practical part of thesis pays attention to the experimentation with the pre-selected sample of person. The test itself was based upon usage of the reaction measurement tool with the optical stimulus for inputs. The objective of the practical part was to compare the influence of caffeine, and its specific amount, on the reaction abilities of selected individuals. Recorded data have been than statically evaluated, and prepared to final comparison. Based on receiving information the unequivocal deduction was determined.

In this thesis were charted information and methodology about reaction time of horses on optical stimulus. As an optical stimulus was used vehement and unforseen movement by white board (500 x 500 mm) on which horses reacted very well. Reaction scanning was made by high-speed video camera MotionScope 9400, which was connected to a computer. In total was evaluated group of 35 horses. The average age was 5.8 years, the average reaction time on optical stimulus was 152 ms. In experiment was group of 14 thoroughbreds and 21 warmbloods. Group contained 4 stallions, 17 geldings and 14 mares. The largest group was represented by 5 years old (10 representatives). By the thoroughbreds was found out reaction time 154 ms, by the warmblood group 150 ms. Differences between breeds were not statistically significant. The lowest average reaction time was measured out by stallions (139 ms), then mares (149 ms) and the highest rate was by geldings (157 ms). The difference between reaction time of geldings and mares was not statistically significant. The lowest rate was measured out by the age group from 2 to 4 years old (142 ms), then group of 6 to 13 years old (156 ms). The highest rate had group of 5 years old (159 ms). The differences between age groups were not upholded as statistically significant. The correlation coefficient expressing relation between age of horses and reaction time on the optical stimulus was found out very low, that means that it is not statistically significant. In this thesis was proved, that as well as humans, horses react more quickly on acoustic stimulus than on optical stimulus.

Uma sequência melódica não depende apenas de eventos discretos, mas também da tonalidade, uma estrutura holística que hierarquiza a expectativa dos ouvintes para as notas que devem ocorrer. Para melhor compreender o funcionamento dos mecanismos cognitivos responsáveis por essa hierarquia, dois experimentos foram propostos. O primeiro experimento verificou se o tempo de resposta simples de um participante a uma nota é influenciado pelas suas características em relação a tonalidade da música, não encontrando nenhuma relação entre os tempos de resposta e as características melódicas dos estímulos. O segundo experimento verificou os tempos de resposta dos participantes para discriminarem uma determinada altura como igual ou diferente a uma altura apresentada em um momento anterior ao momento da coleta. Os resultados mostraram que os participantes são capazes de realizar a tarefa, e apresentaram um tempo de resposta menor para uma nota um tom abaixo da nota esperada, um achado novo. / A melodic sequence not only depends of discrete events, but also of the tonality, a holistic structure that hierarchize the listener expectancy to notes that should occur. To better understand the cognitive mechanisms responsible for this hierarchy, two experiments were developed. The first experiment tested if the simple reaction time of the participants in response to a note is influenced by its tonal characteristics, did not find any correlation between the collected reaction times and the melodic characteristics of the stimuli. The second experiment tested if the participants choice reaction time to discriminate a relative pitch presented in a different moment than a pitch presented earlier to the gathering. The results show that the participants, independently of musical training, are capable of performing the task, and present a smaller reaction time to the note one tone bellow the expected note, a new finding that didnt match the expected characteristics used to guide the participant reaction.

Visual target acquisition is performed during several daily tasks, often requmng time¬dependent behavioural responses towards stimuli. Information processing during such tasks is subject to bottom-up as well top-down influences, which results in an integrated processing mechanism. It follows that if the underlying neural mechanisms can be elucidated, behaviour towards visual stimuli will be better understood, allowing for the development of visual environments that facilitates desired behavioural response. The current study aimed to develop a systems-level approach according to which the mechanisms that underlie visual target acquisition can be understood, by interpreting psychophysical data in terms of the structural and functional organization of the visual system. Empirical work entailed psychophysical experiments and elaborated on previous studies regarding conspicuity areas around and response time towards visual targets. The rationale was that these two measures can be used as an indication of the conspicuity of a target within a specific background, which in turn can be related to the nature of information processing during a target acquisition task. Results showed that a proportional relationship exists between the size of the conspicuity area and a target's perceived conspicuity, with the most conspicuous targets being associated with the largest conspicuity areas. Response time trends showed that target detectability at different positions within the conspicuity area is equal, but that detection performance at positions outside the conspicuity area is greatly influenced by the nature of the background surrounding the target. Interpretation of the results points to the importance of visual attention during target acquisition, which in turn is supported by the structural and functional organization of the visual system. Findings from the psychophysical study presented here, along with the proposed framework of information processing, emphasise that behavioural outcome during visual target acquisition cannot be explained without considering the structural and functional organization of the visual system. / Dissertation (MSc (Human Physiology))--University of Pretoria, 2006. / Physiology / unrestricted

The ability to navigate with limited vision is a skill that is often employed in our daily lives. Navigating without vision to a remembered target has previously been studied. However, not much is known about the attention required to perform blind navigation. We examined the effect of aging and presence of obstacles on the attentional demands of blind navigation. We evaluated reaction time, navigation errors and average walking speed in an 8 meter walking path, with or without obstacles, in the absence of vision. Results showed that older participants had increased reaction time and increased linear distance travelled as opposed to young participants, that obstacles increased reaction time and decreased average walking speed in all participants, and that emitting the reaction time stimulus early in the trial increased the linear distance travelled. Interpretation of the results suggests that aging and presence of obstacles augments the attentional demands of blind navigation.

The stopping of an earlier intended action is best explained in a race between a go process and a stop process (Logan & Cowan, 1984). The finish line, to which each process races, has been likened to a point of no return, specifically one that marks the onset of a final ballistic (unstoppable) process. Of note is the typical relation of reduced go probabilities and faster go latencies at shorter signal onset asynchronies (SOAs). (The SOA is the time interval between presentation of the go signal and presentation of the stop signal.) We report, in some cases, sub-maximal surface electromyograms (EMGs) at onset when trying to stop a maximal speeded action. These data indicate reduced synaptic drive to reach the motor pools as a result of earlier stopping effects and, as such, hold important implications for a theory of control. First, we interpret these data to suggest that the point of no return is phantom. Sub-maximal EMGs indicate a point in the control stream beyond which some EMG will be later observed but, importantly, they fail to mark the onset of a final ballistic process if, once breached, the same process remains subject to further effects of stopping. The alternative interpretation, however, that of a final ballistic process that receives sub-maximal input which results in sub-maximal output (i.e., EMG onset) cannot be ruled out from these data. We used the Hoffmann (H) reflex to probe further the mechanism of control for stopping a voluntary action. The H-reflex, an involuntary reflex that is taken as an index of spinal control, is relevant to the control of stopping because it is typically facilitated a short time before EMG onset. In other words, it provides a window of control within which a final ballistic process would otherwise be expected to locate. Thus, we interpret the effects of stopping on the H-reflex before EMG onset as strong evidence against a final ballistic process. Second, while the race model can explain the relation between the go probabilities, the go latencies and the SOAs, it fails to explain the sub-maximal EMG onsets that describe that same action in some cases. We submit a mechanism of excitatory-inhibitory interaction at all times up to the motor pool to explain both sets of empirical data. The viability of this theory is demonstrated using computer analyses. / Education, Faculty of / Kinesiology, School of / Graduate

The aim of this work is evaluate usual time and frequency of selected traffic situations observation by the driver. A necessary part of this problem is a driver in this context is described herein personality driver and psychological factors that affect it during the process of driving in traffic. The important part is played by visual system driver and his perception of stimuli. The thesis also outlines the problems concerning the importance of transport routes, its environment and transport vehicle for drivers. The practical part is devoted to the evaluation of video recordings in the field driving tests on the basis of which it was possible to determine the frequency and duration of glances in selected situations in traffic.

Název práce: Vliv fyziologického stresu na rychlost reakce v sebeobranné situaci Cíl práce: Cílem práce je zjistit, jaký vliv bude mít fyziologický stres způsobený krátkodobým maximálním zatížením na rychlost jednoduché reakce na vizuální podnět a vysvětlit změny pro oblast sebeobrany a boje zblízka. Metody práce: Na skupině dobře trénovaných osob v oblasti sebeobrany, boje zblízka či bojových sportů (věk: r=29,0 6,6 let; pohlaví: m, n:10), byla aplikována dotazníková metoda pro zjištění základních údajů, charakteru aktivit, které provozují, zdravotního stavu a dalších faktorů ovlivňujících reaktometrii. Následně byli probandi podrobeni reaktometrii zařízením Vienna test system pro zjištění úrovně jednoduché reakce na vizuální podnět. Každý proband absolvoval maximální zatížení na bicyklovém ergometru, aby krátce po skončení zatěžování opakoval reakční test. Po ukončení testu byl probandům odebrán vzorek krve pro zjištění hladiny laktátu v krvi. Naměřené hodnoty reakčních časů byly porovnány pomocí párového t-testu, ostatní možné determinanty pomocí korelační analýzy. Výsledky práce: U sledovaného souboru došlo vlivem krátkodobé maximální zátěže ke statisticky významnému zlepšení jednoduché reakční rychlosti na vizuální podnět a pohotovostního rozměru této reakce, a to v rozmezí 7-10%. Byl potvrzen...