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This thesis presents an investigation into the problems of exploration, map building and collision free navigation for intelligent autonomous mobile robots. The project began with an extensive review of currently available literature in the field of mobile robot research, which included intelligent control techniques and their application. It became clear that there was scope for further development with regard to map building and exploration in new and unstructured environments. Animals have an innate propensity to exhibit such abilities, and so the analogous use of artificial neural networks instead of actual neural systems was examined for use as a method of robot mapping. A simulated behaviour based mobile robot was used in conjunction with a growing cell structure neural network to map out new environments. When using the direct application of this algorithm, topological irregularities were observed to be the direct result of correlations within the input data stream. A modification to this basic system was shown to correct the problem, but further developments would be required to produce a generic solution. The mapping algorithms gained through this approach, although more similar to biological systems, are computationally inefficient in comparison to the methods which were subsequently developed. A novel mapping method was proposed based on the robot creating new location vectors, or nodes, when it exceeded a distance threshold from its mapped area. Network parameters were developed to monitor the state of growth of the network and aid the robot search process. In simulation, the combination of the novel mapping and search process were shown to be able to construct maps which could be subsequently used for collision free navigation. To develop greater insights into the control problem and to validate the simulation work the control structures were ported to a prototype mobile robot. The mobile robot was of circular construction, with a synchro-drive wheel configuration, and was equipped with eight ultrasonic distance sensors and an odometric positioning system. It was self-sufficient, incorporating all its power and computational resources. The experiments observed the effects of odometric drift and demonstrated methods of re-correction which were shown to be effective. Both the novel mapping method, and a new algorithm based on an exhaustive mesh search, were shown to be able to explore different environments and subsequently achieve collision free navigation. This was shown in all cases by monitoring the estimates in the positional error which remained within fixed bounds.

Pain catastrophizing emerges in the literature as one of the most important psychological determinants of both pain itself and the negative outcomes commonly associated with it. However, despite decades of research confirming the impact of catastrophizing, there are still areas that remain unexplored or in which the surface has only been scratched. The overall aim of this dissertation was to expand existing knowledge about catastrophizing and to advance the theoretical framework around the concept. The role of catastrophizing was explored in three distinct areas: during pain in childbirth, in exposure treatment for back pain patients, and in a problem solving context. The findings from the three studies confirmed the vital role of catastrophizing in these areas. Firstly, catastrophizing played a critical role in pain in childbirth; women who catastrophized reported labor pain as more intense and the subsequent recovery period as longer than women who did not catastrophize. Secondly, catastrophizing was identified as a moderator of treatment effect in exposure in vivo for back pain patients with pain-related fear; patients who catastrophized were not helped by the exposure. Thirdly, catastrophizing played a role in a problem solving context; although this is in line with contemporary models such as the misdirected problem solving model, the results suggested a somewhat different pathway to this previous model. Taken together, these findings underscore the instrumental role of catastrophizing in diverse areas and imply a need for catastrophzing to be assessed and addressed in clinical contexts. In addition, the findings highlight a need for further development of the theoretical framework around catastrophizing as well as treatment interventions that directly target catastrophizing. Based on these needs, a new model of catastrophizing was proposed – a model of catastrophizing from a process perspective. In this model, the proposed function of catastrophizing is to down-regulate negative affect, as a form of internal avoidance. The model is a complement to existing theoretical models and provides a framework for developing treatment interventions that directly target catastrophizing, for example by problem solving skills training. Successful interventions for people who catastrophize would lead to several gains – for the individual in less suffering and increased ability to handle pain problems, and for society as a whole in reduced costs for health care for these individuals.

It was the purpose of the present study to compare the effect of intraperitoneal injections of the following drugs on a conditioned approach-avoidance response in mice. These drugs were epinephrine and nor-epinephrine.

This study investigated the effectiveness of aversion therapy to help subjects achieve and maintain a weight loss. The aversion therapy made use of an avoidance conditioning procedure. Slides of fattening foods were paired with the possibility of receiving an electric shock in an attempt to induce anxiety. Slides of non-fattening foods were paired with shock avoidance and consequent anxiety relief.

Experiential avoidance (EA) is a process in which a person attempts to avoid, dismiss, or change experiences such as emotions, behaviors, and thoughts. EA is associated with a number of psychological disorders and is generally harmful to psychological well-being. Various studies have explored the role of EA as a mediator, while others have studied EA as a moderator. The current study aimed to further understand and broaden the knowledge of the role of EA in regard to trauma, substance abuse, aggression, and impulsivity by examining relationships between these variables with EA as a mediator and as a moderator. Experientially avoidant behaviors (i.e., substance abuse, aggression, and impulsivity) were related to higher levels of EA. EA was found to partially mediate the relationship between the number of traumatic experiences and posttraumatic stress disorder (PTSD) symptoms, as well as the relationship between substance abuse and PTSD. EA was also found to moderate the relationship between PTSD symptoms and aggression. Findings from the present study as well as its limitations and future directions for research are discussed.

Avoidance is behaviour that prevents or postpones the occurrence of an aversive stimulus; whereas, escape is behaviour that terminates an aversive stimulus. There are two types of avoidance, both of which prevent an aversive stimulus from occurring. Standard avoidance involves a warning stimulus that predicts an aversive stimulus, reinforced by the termination of the warning stimulus. Alternatively, Sidman or free-operant avoidance does not include a warning stimulus and it is unknown what the exact reinforcing properties are that maintain it. Previous research has found that Betta splendens (Siamese fighting fish) may not engage in Sidman avoidance whereas other fish species including Carassius auratus (goldfish) do. The present study looked at whether Betta splendens could be taught Sidman avoidance when water disturbance is the aversive stimulus, by prompting the fish to emit the avoidance response of crossing over between the two sides of an experimental tank in 30second intervals, and reinforcing the behaviour with a mirror. Results showed an increase in the frequency of independent (i.e., unprompted) crossovers between the sides of the experimental tank resulting in avoidance of water disturbance, an aversive stimulus for these fish. The increase in responding was maintained for one of the three subjects when reinforcement was removed, suggesting that this species can learn Sidman avoidance. / May 2016

Predators select for defensive adaptations, such as stings, toxins, and camouflage color patterns. Madtoms, Noturus, are diminutive catfishes with dorsal and pectoral stings. Thirteen of the 25 nominal species have serrated spines in the pectoral sting and a contrasting pigment pattern. Behavior of two saddled species, N. miurus and N. hildebrandi, and one uniformly colored species, N. leptacanthus, was investigated to test if the pigment pattern is camouflage. Saddle spacing and crypticity of the saddled species were measured against various substrates and were found to be unevenly spaced, which could be camouflage when viewed against gravel. Given substrate choices, madtoms preferred gravel during daylight conditions. In subsequent experiments, all species were given colored gravel to test color vs. texture-based substrate choice and preferred dark substrates. In the presence of a predator stimulus, madtoms preferred gravel at night and dawn. The pigment pattern likely is camouflage when viewed against gravel substrates.

I hypothesize and find that the variation in corporate tax avoidance is jointly determined by firms’ incentive and opportunities to avoid taxes. Specifically, the positive relation between financial constraints (my proxy for an incentive to avoid taxes) and tax avoidance is significantly stronger for firms with high tax planning opportunities (TPO), where TPO is the distance between a firm’s actual and predicted ETRs. I further show that firms with TPOs based on high permanent (temporary) book-tax differences exhibit more permanent (temporary) book-tax differences under financial constraints. From a risk perspective, I find no evidence that financially constrained firms with low TPO exhibit more tax risk but some evidence that those with high TPO do so. In general, the findings in this paper provide evidence consistent with an incentive-opportunity interaction story to help explain differences in corporate tax avoidance.