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Previous studies have investigated links between cognitive ability and a number of factors including age, gender, handedness, musical ability as well as the volume and surface area of certain brain structures, However, in these studies either the explanatory variables are analysed independently of each other, or the investigation is based on a separate analysis for individual cognitive outcomes (e.g. language, visuospatial, etc.) The main objectives of this thesis are(1) to develop general multivariate models, which include mixed-effects terms, to account for the correlation in the data, (2) to explore the possible associations in children and adults between multiple cognitive ability test scores and the range of factors mentioned above by simultaneously applying the multivariate models designed in (1), and (3) to investigate the possible effects of missing data on the results. To meet these objectives, a range of statistical and stereological methods was employed: Multivariate linear and linear mixed models were developed and fitted to multiple datasets. The approach used took into account the correlation of clustered data, the correlation between outcomes as well as the association between explanatory variables and a linear combination of the outcomes. Stereological methods were used to estimate the volume and surface area of a region of the brain called Broca's area, using magnetic resonance images. Also, the latest formulae in error prediction for these stereological estimates were described and applied to the data. Results from the fitted multivariate linear mixed model to a dataset of l l-year old children (n= 1184 3) showed that children whose writing hand has less hand skill than the opposite hand performed worse, on average, in both reading and maths scores, than those children whose writing hand had more hand skill than the opposite hand. A multivariate linear model fitted to a dataset of adults (n=142) revealed that the gender difference found in the non-musician groups for the vocabulary and arithmetic scores was not present in the musician group. Multivariate linear models were subsequently fitted to a subset of this cohort containing volume and surface area estimates of Broca's area (n=39). Musicians were associated with Broca's area being less convoluted in the right hemisphere than non-musicians. Other associations investigated were not found to be statistically significant. Inverse probability weighting was then used to take the missing data into account for each of the analyses (aim (3)). The results and interpretations determined from the fitted multivariate models were consistent with the analyses when the missing data were accounted for. Only those results for the children dataset changed slightly, but not enough to alter the interpretations of the results. This adds weight to the belief that the results of the multivariate analyses gave a reasonably accurate description of the variability that exists within the children and adult datasets.

The P-300 (commonly abbreviated as P3) is one of the most researched phenomena in the field of cognitive neuroscience. One of the many applications that derived from the discovery of this brain signal is deception detection. This practice commonly utilises the P3 in Concealed Information Tests (also called Guilty Knowledge Tests). As the name suggests, this type of test allows experimenters to detect information that is being concealed by a suspect. An example of such a situation, in practice, could involve a terrorist concealing their identity by pretending to have a different name. This example is particularly relevant to this thesis, which focuses on identity deception. More in detail, we propose the development of a deception detector which utilises Rapid Serial Visual Presentation (RSVP) as a presentation technique. In this way, we present stimuli on the fringe of awareness, greatly reducing the possibilities of applying countermeasures, whose use is an issue in many deception detector implementations. U sing the P3 is advantageous as it can be easily measured by electroencephalography; the high temporal resolution and reduced cost of EEG are appropriate for rapid deployment in field situations. Recorded data can then be analysed utilising Randomisation, a form of Monte Carlo Resampling, particularly useful in performing statistical inferences at the individual level. We tested this implementation and replicated it various times: different types of concealed information were utilised (namely birthdays and first names). As will be demonstrated, our system was successful, achieving high hit rates and low false alarm rates. We also instructed participants to deliberately attempt to confound the deception detector and we explain how our deception detector can resist their application. Finally, we discuss a number of alternative analyses on the presented data. We studied the relationship between the two types ofP3 that were elicited in our experiments: the P3a and the P3b. The randomisation method proposed is also examined under balanced and unbalanced situations. Finally, we compare "standard" ERP analyses with a novel tool that we call Spectral Mass, that employs time-frequency transforms in place of averaging.

This thesis aimed to examine the effects of glucose drink administration on sensorimotor function (studies 1 - 3) and declarative memory (study 4). Glucose had no effect on a modified version of the Hick task in study 1. However in study 2 we observed that glucose slowed reaction times (RTs) during the initial performance of the Eriksen flanker task. One possible reason for this effect is that glucose only slows sensorimotor function when a response is weakly associated with a stimulus, such as at the beginning of task performance. In study 1 stimulus-response (S-R) associations may have been too strong to observe a glucose slowing effect. Here participants performed a greater number of training trials and stimuli were arguably mapped more directly to a response compared to study 2. In study 3 we tested the hypothesis that glucose slows sensorimotor function when S-R associations are weak. Here we used a letter version of the Eriksen flanker task and kept S-R association consistently low by changing the stimulus set to a novel pair of letters every 80 trials. We found that glucose constantly slowed RTs for the duration of this task, a result which is congruent with the hypothesis that glucose slows sensorimotor function when S-R associations are weak. In study 4 we focused on the effects of glucose administration on declarative memory function and sought to determine whether glucose affected the encoding of stimuli in a word recognition task. Here we used ERPs as an online measure of encoding processes. Our findings were that glucose enhanced recognition performance, replicating the well established effect that glucose- facilitates declarative memory. Furthermore, during encoding, glucose affected ERP components associated with early sensory processing, visual word-form generation, lexical/semantic access and long-term memory encoding/consolidation. Furthermore there was a correlation between recognition performance and the degree to which glucose amplified the N400 component, an ERP potential associated with lexical/semantic access. The results of this study therefore indicate that glucose modulates encoding processes and that these effects may, at least partially, underlie the glucose facilitation of declarative memory.

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