Pseudoneglect and visual attention networks

Pseudoneglect represents the tendency for healthy individuals to show a slight but consistent bias in favour of stimuli appearing in the left visual field. The bias is often measured using variants of the line bisection task. An accurate model of the functional architecture of the visuospatial attention system must account for this widely observed phenomenon, as well as for modulation of the direction and magnitude of the bias within individuals by a variety of factors relating to the state of the participant and/or stimulus characteristics. To date, the neural correlates of pseudoneglect remain relatively unmapped. In the current thesis, I employed a combination of psychophysical measurements, electroencephalography (EEG) recording and transcranial direct current stimulation (tDCS) in an attempt to probe the neural generator(s) of pseudoneglect. In particular, I wished to utilise and investigate some of the factors known to modulate the bias (including age, time-on-task and the length of the to-be-bisected line) in order to identify neural processes and activity that are necessary and sufficient for the lateralized bias to arise. Across four experiments utilising a computerized version of a perceptual line bisection task, pseudoneglect was consistently observed at baseline in healthy young participants. However, decreased line length (experiments 1, 2 and 3), time-on-task (experiment 1) and healthy aging (experiment 3) were all found to modulate the bias. Specifically, all three modulations induced a rightward shift in subjective midpoint estimation. Additionally, the line length and time-on-task effects (experiment 1) and the line length and aging effects (experiment 3) were found to have additive relationships. In experiment 2, EEG measurements revealed the line length effect to be reflected in neural activity 100 – 200ms post-stimulus onset over source estimated posterior regions of the right hemisphere (RH: temporo-parietal junction (TPJ)). Long lines induced a hemispheric asymmetry in processing (in favour of the RH) during this period that was absent in short lines. In experiment 4, bi-parietal tDCS (Left Anodal/Right Cathodal) induced a polarity-specific rightward shift in bias, highlighting the crucial role played by parietal cortex in the genesis of pseudoneglect. The opposite polarity (Left Cathodal/Right Anodal) did not induce a change in bias. The combined results from the four experiments of the current thesis provide converging evidence as to the crucial role played by the RH in the genesis of pseudoneglect and in the processing of visual input more generally. The reduction in pseudoneglect with decreased line length, increased time-on-task and healthy aging may be explained by a reduction in RH function, and hence contribution to task processing, induced by each of these modulations. I discuss how behavioural and neuroimaging studies of pseudoneglect (and its various modulators) can provide empirical data upon which accurate formal models of visuospatial attention networks may be based and further tested.

An explanation of consumer trust recovery in a food retailer

An organization trusted by consumers enjoys a number of benefits. Unfortunately, instances of trust-damaging events involving organizations happen often. Damaged consumer trust in an organization has numerous negative consequences for the organization and for consumers. Currently, there is a paucity of theory about consumer trust recovery. So, understanding why and how consumer trust recovery occurs is timely, and theoretically and practically relevant. However, the findings from this study suggest that we need to distinguish between two kinds of consumer trust recovery. The first (I call it unconscious consumer trust recovery) refers to trust recovery that occurs without the consumer being fully conscious of it. In other words, a consumer is aware of their damaged trust during the scandal, but is not aware that their trust in the organization has improved. The consumer does not think about his or her recovered trust, just as they did not think about their level of trust before the scandal. The consumer trust is habitual. The second (I call it conscious consumer trust recovery) refers to an improvement in damaged trust where the consumer is fully conscious of their trust recovery. In other words, in conscious trust recovery the consumer is aware that the scandal damaged their trust in the organization. Also, after the scandal, in contrast to unconscious trust recovery, in conscious trust recovery the consumer is also fully aware that he trusts the organization as much or more than during the scandal. My aim is to inductively develop a theory explaining each type of consumer trust recovery. To do so, I use Charmazian grounded theory methodology, because this methodology is developed for theory-building from data and is aligned with the philosophical underpinnings of this study. The empirical context for this study is the meat adulteration scandal (“the horse meat scandal”) in 2013 in the UK. I collect and analyse empirical data about both types of trust recovery in an organization from 31 consumers that experienced both types. My analysis shows that when consumers perceive the scandal as less important, they experience unconscious trust recovery. This happens because the reduced importance of the scandal leads to a shift in consumers’ attention, which in turn leads to their inattentiveness to the scandal. Consumer inattentiveness is an immediate antecedent of unconscious trust recovery. Conscious consumer trust recovery occurs because consumers see cues indicating to them that the food retailer has improved product control systems, which in turn leads to consumer perceptions of the organization’s renewed ability. Consumer perception of renewed ability is an immediate antecedent of their conscious trust recovery. My findings lead me to make three main theoretical contributions to the theory of trust recovery in general and to consumer trust recovery in particular. The first contribution lies in showing that there are two types of consumer trust recovery in an organization, not one, as previously conceptualised, and that the same consumers can experience both types. The second contribution is a theory of unconscious consumer trust recovery in an organization that involves three concepts: consumers’ perceived importance of the scandal, consumers’ shift of attention, and consumer inattentiveness. The third contribution is the finding that conscious recovery of consumer trust occurs even when existing theory of trust recovery would predict that it would not. This study can help managers aiming to repair consumer trust in an organization by identifying a set of antecedents and underlying mechanisms that can guide such trust repair.

Pricing derivatives with stochastic volatility

This Ph.D. thesis contains 4 essays in mathematical finance with a focus on pricing Asian option (Chapter 4), pricing futures and futures option (Chapter 5 and Chapter 6) and time dependent volatility in futures option (Chapter 7). In Chapter 4, the applicability of the Albrecher et al.(2005)'s comonotonicity approach was investigated in the context of various benchmark models for equities and com- modities. Instead of classical Levy models as in Albrecher et al.(2005), the focus is the Heston stochastic volatility model, the constant elasticity of variance (CEV) model and the Schwartz (1997) two-factor model. It is shown that the method delivers rather tight upper bounds for the prices of Asian Options in these models and as a by-product delivers super-hedging strategies which can be easily implemented. In Chapter 5, two types of three-factor models were studied to give the value of com- modities futures contracts, which allow volatility to be stochastic. Both these two models have closed-form solutions for futures contracts price. However, it is shown that Model 2 is better than Model 1 theoretically and also performs very well empiri- cally. Moreover, Model 2 can easily be implemented in practice. In comparison to the Schwartz (1997) two-factor model, it is shown that Model 2 has its unique advantages; hence, it is also a good choice to price the value of commodity futures contracts. Fur- thermore, if these two models are used at the same time, a more accurate price for commodity futures contracts can be obtained in most situations. In Chapter 6, the applicability of the asymptotic approach developed in Fouque et al.(2000b) was investigated for pricing commodity futures options in a Schwartz (1997) multi-factor model, featuring both stochastic convenience yield and stochastic volatility. It is shown that the zero-order term in the expansion coincides with the Schwartz (1997) two-factor term, with averaged volatility, and an explicit expression for the first-order correction term is provided. With empirical data from the natural gas futures market, it is also demonstrated that a significantly better calibration can be achieved by using the correction term as compared to the standard Schwartz (1997) two-factor expression, at virtually no extra effort. In Chapter 7, a new pricing formula is derived for futures options in the Schwartz (1997) two-factor model with time dependent spot volatility. The pricing formula can also be used to find the result of the time dependent spot volatility with futures options prices in the market. Furthermore, the limitations of the method that is used to find the time dependent spot volatility will be explained, and it is also shown how to make sure of its accuracy.