Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 111-112).

Not available / text

Signal detection theory predicts that costs associated with recognition errors, specifically failing to respond to relevant stimuli (missed detection) and responding to erroneous ones (false alarms), shape receiver permissiveness in animal communication systems. Fitness costs of missed detection and false alarms in response to sexual signals differ between the sexes, and are usually higher for females than males. This asymmetry in costs predicts that males should be more permissive than females in their responses to signals. In my dissertation I investigate the behavioral responses of male and female túngara frogs, Physalaemus pustulosus, to mating signals and sounds associated with such calls. Specifically I explore the following topics: i) responses of the sexes to call complexity, ii) perception of congeneric mating calls by males and females, iii) responses of males to the conspecific call compared to those of extant heterospecifics, iv) effect of sounds associated with increased predation risk in reproductive decisions, and v) effect of the task performed by each sex on signal permissiveness. My findings indicate that recognition errors are higher for males than females as predicted by the different costs associated with recognition errors for each sex. Males respond to a broader range of calls than females. Despite the differences, evolutionary history has left a footprint on the brain of both sexes. In addition, I found that females behaved more cautiously than males suggesting that the sexes balance the risk of predation and the cost of cautious mating strategies differently. In the mating system of túngara frog, as in many others, sexual signals elicit different tasks in the different sexes, female phonotaxis and male calling. Therefore, the sexual differences in decision making I found could be either sex-specific independent of task, or task-specific independent of sex. Here I show that sexual differences in receiver permissiveness are motivated by differences due to the typical reproductive tasks displayed by the sexes. / text

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

No description available.

No description available.

Guidelines for using style to improve computer program comprehension have often been proposed without empirical testing. This thesis reports on the results of three controlled experiments that investigated ways program style may be used to aid comprehension of source code listings. Experiments 1 and 2 were conducted using advanced computer science students as subjects and short Pascal programs. Results showed that student programmers used meaningful identifier names as important sources of information during comprehension of short programs. A review of the literature showed the need for the thesis' proposed methodology for designing controlled experiments on program comprehension that produce results which generalize well to situations involving professional programmers working on real world tasks. This methodology was used to design Experiment 3. Text comprehension researchers have investigated the use of signaling, or the placement of non-content information, in a text in order to emphasize certain ideas and/or clarify the organization. Experiment 3 investigated the role of signaling in another domain, that of computer program source code listings. The experiment had professional programmers study a 913-line C program. Three types of signals were investigated: preview statements, headings, and typographic cueing. The major results were (a) meaningful module names served as headings in the source code listing and helped professional programmers understand and locate information in the program; (b) header comments, when written as preview statements, helped professional programmers understand and locate information in the program; (c) typographic cueing, designed to provide emphasis and segmentation cues, helped programmers understand the program; and (d) the effects of meaningful names, header comments, and typographic cueing were additive. No significant interactions of effects were observed. Based on these results, guidelines are proposed for ways programmers may use comments and module names in source code to act as signals that aid future readers. In addition, guidelines are suggested for adding typographic signaling to provide emphasis to the comments and names. / Graduation date: 1992

After defining the structure to a signal detection scheme, this dissertation describes and addresses some of the unresolved issues associated with its use when the interference encountered is impulsive. The alpha-stable (alpha-S) family of distributions is used as a model of this interference due to its physical interpretation and its general form. Despite its attractive features, difficulties arise in using this distribution due to, amongst other things, the lack of a general closed form expression for its probability density function. Relevant to the detection scheme used, this affects parameter estimation, signal detector design and goodness-of-fit tests. Significant contributions are made in the latter through the introduction of characteristic function based test that uses the parametric bootstrap. A modification of this test is then made to define a test of the level of impulsive behaviour - again the parametric bootstrap is employed to maintain levels of significance for this and another test based on testing the alpha-S parameter values. The performance of these tests is examined under simulated and two sources of real, impulsive data, namely human heart rate variability and fluctuations in stock prices. Once the appropriateness of the model assumption has been verified, the final, signal detection process may take place. Detectors based on the locally optimum criterion and approximations to it are described and compared to their rank-based counterparts. Results are presented that suggest compelling arguments based on performance and computational complexity for the consideration of rank-based techniques.Keywords: Impulsive behaviour, alpha-stable distribution, stable laws, Gaussianity testing, parameter estimation, goodness-of-fit, parametric bootstrap, signal detection, locally optimum detectors, rank-based detectors.