The use of hypermedia for educational purposes gained a great deal of importance for educators. There are many opportunities provided to learners by these environments such as independence from time and place, availability and accessability of the course material, non-linear interaction that provides the learner to regulate his/ her own learning and so on. Although many advantages of hypermedia environment are suggested in the literature, there are also many studies concerning with learning in hypermedia environment concluding that many learners face with problems on these settings. This qualitative study aimed to investigate the affects of three important factors in terms of learning with hypermedia revealed by the literature / cognitive styles, computer competency levels, and domain knowledge levels of the students. To the purpose of the study, participants from a web-enhanced course were selected considering these factors, and interviews and observations were conducted to reveal their learning strategies. Results indicated some differences among the different cognitive style groups of students in terms of their preferred learning strategies. Computer competency levels of the students were also found to be quite important in terms of their patterns to use the hypermedia program. Students&rsquo / prior knowledge levels were also important in this study, since different needs and expectations were revealed related to the domain knowledge levels of the participants. Furthermore, a deep understanding about the behaviors, experiences, feelings, and expectations of the students in an instructional hypermedia environment related to suggested different characteristics were gained at the end of the study.

One of the lasting concerns in audiology is the unexplained individual differences in speech perception performance even for individuals with similar audiograms. One proposal is that there are cognitive/perceptual individual differences underlying this vulnerability and that these differences are present in normal hearing (NH) individuals but do not reveal themselves in studies that use clear speech produced in quiet (because of a ceiling effect). However, previous studies have failed to uncover cognitive/perceptual variables that explain much of the variance in NH performance on more challenging degraded speech tasks. This lack of strong correlations may be due to either examining the wrong measures (e.g., working memory capacity) or to there being no reliable differences in degraded speech performance in NH listeners (i.e., variability in performance is due to measurement noise). The proposed project has 3 aims; the first, is to establish whether there are reliable individual differences in degraded speech performance for NH listeners that are sustained both across degradation types (speech in noise, compressed speech, noise-vocoded speech) and across multiple testing sessions. The second aim is to establish whether there are reliable differences in NH listeners' ability to adapt their phonetic categories based on short-term statistics both across tasks and across sessions; and finally, to determine whether performance on degraded speech perception tasks are correlated with performance on phonetic adaptability tasks, thus establishing a possible explanatory variable for individual differences in speech perception for NH and hearing impaired listeners.

We humans depend heavily on cognitive control to make decision and execute goal-directed behaviors, without which our behavior would be overpowered by automatic, stimulus-driven responses. In my dissertation, I focus on a brain region most implicated in this crucial process: the anterior cingulate cortex (ACC). The importance of this region is highlighted by lesion studies demonstrating diminished self-initiated behavior, or apathy, following ACC damage, the most severe form of which results in the near complete absence of speech production and willed actions in the presence of intact motor ability. Despite decades of research, however, its precise function is still highly debated, due particularly to ACC’s observed involvement in multiple aspects of cognition. In my dissertation I examine ACC function according to recent developments in reinforcement learning theory that posit a key role for ACC in motivating extended behavior. According to this theory, ACC is responsible for learning task values and motivating effortful control over extended behaviors based on those learned task values. The aim of my dissertation is two-fold: 1) to improve understanding of ACC function, and 2) to elucidate the contribution of ACC to depression, as revealed by individual differences in several personality traits related to motivation and reward sensitivity in a population of healthy college students. It was hypothesized that these different personality traits express, to greater or lesser degrees across individuals, ACC function, and that their abnormal expression (in particular, atypically low motivation and reward sensitivity) constitute hallmark characteristics of depression. First, this dissertation reveals that reward positivity (RewP), a key electrophysiological signature of reward processing that is believed to index the impact of reinforcement learning signals carried by the midbrain dopamine system on to ACC, is sensitive to individual differences in reward valuation, being larger for those high in reward sensitivity and smaller for those high in depression scores. Second, consistent with a previous suggestion that people high in depression or depression scores have difficulty using reward information to motivate behavior, I find these individuals to exhibit relatively poor prolonged task performance despite an apparently greater investment of cognitive control, and a reduced willingness to expend effort to obtain probable rewards, a behavior that was stable with time on task. In contrast, individuals characterized by high persistence, which is indicative of good ACC function, exhibited high self-reported task engagement and increasing effortful behaviors with time on task, particularly for trials in which reward receipt was unlikely, suggesting increased motivational control. In sum, this dissertation emphasizes the importance of understanding the basic function of ACC as assessed by individual differences in personality, which is then used to understand the impact of its dysfunction in relation to mental illnesses. / Graduate

The following thesis presents the results of a mixed-design study (quasi-experimental and true experimental) testing an integrated model of human risk-taking behavior, defined statistically as a preference for variance in outcomes. The research presented examines the relationships among early-life environmental conditions (i.e., harshness and unpredictability), life-history strategy, and risk-taking behavior for primary resources under various "resource-budget" conditions consisting of deprivation and non-deprivation in two areas: (1) Social-inclusion and (2) caloric "Energy-budget." Two hundred and forty seven (N=247) university students participated in the research. In session one, participants completed multiple questionnaires assessing levels of environmental harshness and unpredictability experienced during development and individual life-history strategy. In session two, participants were pseudo-randomly assigned to experience laboratory induced deprivation or non-deprivation in one of two possible areas: Social-inclusion or caloric "Energy-budget." Following the experimental manipulations, participants played two different behavioral risk-taking tasks: (1) The Wheel Spin Risk Task which required participants to select between a low variance "safe" wheel and a high variance "risky" wheel in an attempt to earn either points or food rewards (depending upon study condition). (2) The Operant Risk Taking Task which required participants to select between a low variance "safe" keyboard key which produced constant rewards and a high variance "risky" keyboard key which produced variable rewards (points or food, depending upon study condition). The results of the multivariate analyses supported main effects only (no moderation) between the characteristics of the early-life environment, life-history strategy, and the experimental manipulations on risk-taking behavior. Specifically, early-life harshness was significantly associated with a faster life-history strategy in participants. Participants with a faster life-history strategy were significantly more likely to select the risky spin wheel on the Wheel Spin Risk Task than were slower life-history strategy participants who were more likely to select the safe spin wheel. Furthermore, participants who experienced the deprivation experimental manipulations behaved more risky on the Operant Risk-Taking Task (for reward amount) than did participants exposed to the non-deprivation manipulations in the study. Interestingly, this effect was domain-general in that deprivation in either Social-inclusion or Energy-budget was associated with risk taking for both social points and for food rewards. The results of this study suggest that life-history strategy is predictive of instrumental risk-taking behavior for reward amount and that deprivation in adaptive areas like Social-inclusion and Energy-budget enhances risk-taking behavior for primary rewards in a domain-general manner as opposed to a domain-specific manner.

Older adults increasingly face difficult decisions in life threatening contexts as they move closer to death, become more likely to be diagnosed with life threatening diseases, and encounter more death within their social network (Greenberg, 2011). The purpose of this research was to understand the effect of a life-threatening decision context centered around cancer, self-esteem, other individual difference factors and cancer experience on older adults’ decision making competence, and preferences for collaborative decision making. Study participants were recruited through online circulation of the study recruitment flyer and in-person solicitations at meetings and other events at community locations (senior centers, civic group centers, and churches, etc.). Participants age 55-90 (N=202) were randomly assigned to either a mundane or life threatening condition and asked to complete the corresponding survey packet containing a measurement questionnaire. Analyses consisted of a series of analyses of variance (ANOVA) and regressions. The dependent variables were 3 major components of the DeBruin et al. (2007) Adult Decision Making Competence Scale: (a) Resistance to Framing, (b) Resistance to Sunk Cost Bias, and (c) Over/under confidence, in addition to a measure of Maximizing Tendency (Diab et al., 2008). Analyses revealed mixed results. Decision context did have an effect on decision making competence, while self-esteem showed little effect. No main effects or interactions were found between decision context, self-esteem, and preferences for collaborative decision making. Individual difference factors did effect decision making competence, with future time perspective, risk tolerance, and ego-integrity emerging as significant predictors. Furthermore, compelling results emerged pertaining to the effect of previous cancer experience on decision making competence. Results highlight the lasting effect of context and a previous cancer diagnosis on decision making competence and have implications in health care, psycho-oncology, and treatment decision making domains.

Hypermedia Learning Systems (HLS) are being used increasingly widely in Higher Education, offering non-linear navigation through complex learning materials and, it is argued, leading to improve cognitive flexibility. For some learners, though, nonlinear navigation in HLS leads to higher levels of disorientation, which can have an impact on their learning performance and attitudes towards the learning system. There has been significant research into the factors that can influence individual learners‘ experiences. For example, a number of studies have confirmed that individual differences such as cognitive style, domain knowledge and computer experience affect individuals‘ levels of disorientation and learning performance, and influence their attitudes towards HLS. It has also been suggested that instructional aids (in the form of certain visual elements and audio elements) can reduce levels of disorientation and, in turn, increase learning performance in, and positive attitudes towards, HLS for some learners. However, existing studies have tended to look at only a subset of these three individual differences in relation to an individual and/or consider only a small number of visual instructional aids. No study up to this point has considered the impact of cognitive style, domain knowledge and computer experience on disorientation, learning performance and attitudes in a HLS that incorporates a full range of visual instructional aids. In terms of the research related to audio instructional aids, no studies have looked into the effects of audio aids and these three individual differences in relation to disorientation, learning performance and attitudes in HLS. This thesis addresses these two shortcomings through two experiments. The aim of experiment 1 was to examine the effects of and between these three individual differences with respect to disorientation, learning performance and attitudes in two versions of a HLS: one that incorporated the set of visual instructional aids and one that did not. Experiment 2 aimed to do the same, but with respect to a HLS that provided audio instructional aids. The experiments used quantitative and qualitative approaches to gather data to address a set of research questions and research hypotheses. The participants were 384 university students from across London. The Cognitive Style Analysis (CSA) test was administered to determine participants‘ field dependence, and participants‘ demographic information, levels of computer experience and levels of prior knowledge were gathered using questionnaires. Learning performance was measured through achievement tests and a practical task. Levels of disorientation were measured using questionnaires, and attitudes were assessed using questionnaires and interviews. Participants were also observed when they were interacting with the HLS to perform learning tasks. A number of interesting results were revealed. Significant effects were found between the three individual differences with respect to disorientation, learning performance and attitudes in the HLS that provided no instructional aids. No significant effects were found between the three individual differences with respect to disorientation or learning performance in the other two versions of the HLS – those providing visual and audio instructional aids. Significant effects were found between the three individual differences with respect to the use of the visual and audio instructional aids to perform learning in the HLS. No significant effects were found between the three individual differences with respect to attitudes in the HLS that provided visual instructional aids. Significant effects were found between the three individual differences with respect to attitudes in the version that provided audio instructional aids. Analysis of the results led to the framing of a set of HLS design guidelines which are presented in this thesis. Finally, an agenda for future research leading on from the study‘s findings is presented.

In both the private and work spheres, multitasking among three or more activities has become and is continuing to evolve as a pervasive element of everyday life, and recent technological advances only seem to be exacerbating the process. Despite attempts to understand the mental processes that let humans successfully multitask, little is known about the functional cognitive level at which these mental processes take place. This thesis makes a case for the involvement of spatial ability (among other cognitive abilities) in successful multitasking behavior. It focuses on the importance of the cognitive off-loading of executive control demands onto spatial ability, due to the inherent complexity of relationships between task goals and deadlines in multitasking scenarios. Importantly, it presents a working hypothesis—the spatiotemporal hypothesis of multitasking—as a tool for making specific predictions about multitasking performance, based on individual and sex differences in spatial ability. In Study 1, individual differences in spatial ability and executive functions emerged as independent predictors of multitasking performance. When spatial ability was decomposed into its subcomponents, only the coordinate (metric), but not categorical (nonmetric), processing of spatial relations was related to multitasking performance. Males outperformed females in both spatial ability and multitasking, and the effects were moderated by menstrual changes, in that sex differences in coordinate spatial processing and multitasking were observed between males and females in the luteal phase of the menstrual cycle, but not between males and females at menses. In Study II, multitasking performance reflected age- and sex-related differences in executive functioning and spatial ability, suggesting that executive functions contribute to multitasking performance across the adult life span, and that reliance on spatial skills for coordinating deadlines is reduced with advancing age. The results of Study III, in which the spatiotemporal hypothesis was directly scrutinized, suggest that the spatial disruption of multiple deadlines interferes with multitasking performance. Overall, these findings suggest that multitasking performance, under certain conditions, reflects independent contributions of spatial ability and executive functioning. Moreover, the results support the distinction between categorical and coordinate spatial processing, suggesting that these two basic relational processes are selectively affected by female sex hormones and are differentially effective, even across the age span, in transforming and handling temporal patterns as spatial relations in the context of multitasking. Finally, fluctuations of sex hormones exhibit a modulating effect on sex differences in spatial ability and multitasking performance. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>

There has been an increasing focus on web-based instruction (WBI) systems which accommodate individual differences in educational environments. Many of those studies have focused on the investigation of learners’ behaviour to understand their preferences, performance and perception using hypermedia systems. In this thesis, existing studies focus extensively on performance measurement attributes such as time spent using the system by a user, gained score and number of pages visited in the system. However, there is a dearth of studies which explore the relationship between such attributes in measuring performance level. Statistical analysis and data mining techniques were used in this study. We built a WBI program based on existing designs which accommodated learner’s preferences. We evaluated the proposed system by comparing its results with related studies. Then, we investigated the impact of related individual differences on learners’ preferences, performance and perception after interacting with our WBI program. We found that some individual differences and their combination had an impact on learners' preferences when choosing navigation tools. Consequently, it was clear that the related individual differences altered a learner’s preferences. Thus, we did further investigation to understand how multiple individual differences (Multi-ID) could affect learners’ preferences, performance and perception. We found that the Multi-ID clearly altered the learner’s preferences and performance. Thus, designers of WBI applications need to consider the combination of individual differences rather than these differences individually. Our findings also showed that attributes relationships had an impact on measuring learners’ performance level on learners with Multi-ID. The key contribution of this study lies in the following three aspects: firstly, investigating the impact of our proposed system, using three system features in the design, on a learner’s behavior, secondly, exploring the influence of Multi-ID on a learner’s preferences, performance and perception, thirdly, combining the three measurement attributes to understand the performance level using these measuring attributes.

This thesis presents six original experiments investigating the relationship between age-related gains and losses in cognitive and emotional abilities and consumer decision making. Novel tasks designed to closely resemble real consumer decisions were used to assess how older and younger adults fare when making everyday decisions. Experiments 1 and 2 examined the relationship between consumer decision making and measures of fluid intelligence, crystallised intelligence and numeric ability in older and younger adults. The data revealed that numeric ability and fluid intelligence independently predicted consumer decision making in older adults. In Experiment 1, participants made factual and inferential decisions about utility suppliers. Findings were corroborated in Experiment 2 using a larger sample and an additional consumer decision task based on selecting a mobile phone provider. Experiment 2 also revealed numeric ability as an independent predictor of young adult’s consumer decision making. Experiment 3 assessed the interplay between age, cognitive resources and emotion regulation. Cognitive resources were assessed by the number of times older and younger adults decided to stick with a pre-selected option, switch to an alternative option or decide in the future. Results suggested that older and younger adults required differing amounts of resources to regulate emotions in accordance with different emotion regulation strategies. Older adults made better consumer decisions when instructed to regulate their emotions by way of reappraisal and younger participants made better consumer decisions when instructed to regulate their emotions using suppression. These results were contrary to what was expected based on previous research on emotion regulation. Because of this, two exploratory experiments were conducted on young adults in an attempt to identify a reliable methodology for inducing and measuring affects more typically associated with self-regulation. These experiments revealed some surprising findings. Participants exposed to manipulations high in terms of cognitive demand made better subsequent consumer decisions than participants placed in less demanding conditions. It was hypothesised that participants exposed to demanding manipulations were primed to make more adaptive consumer decisions. A final experiment tested the effect of age and instruction manipulation on consumer decision making. The relationships between cognitive measures of individual differences and decision making were again measured. Results substantiated previous findings revealed in Experiments 1 and 2 insofar that fluid intelligence was found to independently predict consumer decision making performance in older adults. Fluid intelligence and numeric ability predicted consumer decision making in younger adults. In terms of instruction effects, younger and older adults made better decisions when asked to do so in a rational manner compared to an intuitive manner. It is believed that this work represents some of the first of its kind to study the impact of ageing on cognitive ability and decision making using tasks representative of existing consumer decisions in terms of context and response options. The findings presented provide a valid and unique insight into how cognitive and emotional ability changes with age and the subsequent implications this has when making consumer decisions. This thesis concludes with the theoretical and practical implications for the ageing consumer.

Psychomotor stimulant abuse is a significant public health problem. While many individuals experiment with stimulants, there is marked variability in individuals' behavioral and subjective response to these drugs and these differences may be associated with their risk for abuse. One characteristic shown to be associated with drug abuse is sensation seeking, defined as the seeking of novel sensations and experiences and the willingness to take risks for the sake of such experiences. While observational studies have shown that individuals with elevated sensation seeking are more likely to report stimulant use and abuse, less clear is whether subjective and behavioral response to acute stimulant administration may vary as a function of sensation seeking status. We recently completed an outpatient laboratory study in which 37 healthy adults received repeated opportunities to sample and choose between d-amphetamine (d-AMPH; 5, 10, 20 mg/70kg) or placebo. That study provided an opportunity to examine associations between sensation seeking and d-AMPH choice and subjective response under rigorous double-blind experimental conditions. The Zuckerman Sensation Seeking Scale V was administered at intake, providing a Total sensation seeking score as well as four subscales (i.e., Experience Seeking, Disinhibition, Thrill and Adventure Seeking, Boredom Susceptibility). We hypothesized that elevated sensation seeking at intake would be associated with increased preference for d-AMPH over placebo in subsequent choice sessions, as well as greater positive d-AMPH subjective effects. Among males, increased baseline sensation seeking was associated with increased d-AMPH choice and positive subjective effects at the 5 and 10 mg/70 kg doses. Among females we found no significant associations between sensation seeking and d-AMPH choice or subjective effects. Finally, when the association between sensation seeking and other baseline characteristics was examined, there was a significant positive association with lifetime drug use as well as impulsivity. Taken together, our data suggest that elevated sensation seeking in males may be associated with increased sensitivity to d-AMPH reinforcement and positive subjective effects, suggesting increased vulnerability for stimulant use and abuse.