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Title: Activation of numerical representations : sources of variability
Author: Mitchell, Thomas
ISNI:       0000 0004 5348 4280
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2015
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This thesis presents an investigation into sources of variability in activating and processing numerical information. Chapter 1 provides an overview of research literature exploring the ways in which magnitude information can be represented, and how models relating to number information have developed. These theoretical models are addressed in relation to the neural representation of number, and the range of behavioural markers which suggest an association between spatial and numerical processing. Chapter 2 using a dual-task paradigm investigated whether magnitude information is accessed on perceiving numbers, or if this information is linked to response selection or execution. Previous research studies investigating this question produced inconsistent findings (Oriet, Tombu & Jolicoeur, 2005; Sigman & Dehaene, 2005) with regard to the locus of magnitude processing; the findings of Experiments 1-3 reliably support access to magnitude information during response selection. Chapter 3 explored the activation of spatial-numerical response associations, where response-irrelevant magnitude information was not represented by a single stimulus (i.e. an Arabic digit) but by a numerosity representation. Experiments 4-7 found a strong association between spatial-orientation processing and numerical magnitude, but no association with perceptual-colour processing, extending previous work by Fias, Lammertyn and Lauwereyns (2001) regarding the neural overlap between the attended and irrelevant stimulus dimensions. However the strength of this association was found to be inconsistent across the number range. Chapter 4 investigated the impact of healthy aging on the presence of neural-overlap in processing spatial-numerical information, further developing the paradigm used in Chapter 3, and addressed direct predictions from the literature as to how age should influence these associations (Wood, Willmes, Nuerk & Fischer, 2008). Experiments 8-11 found evidence for spatial-numerical associations across the lifespan, but that the strength of these effects were moderated by 5 task instruction. Chapter 5 was designed to assess aging differences in numerical and spatial processing with a battery of tests and the extent to which other sources of individual difference (sex, embodiment) have a measureable impact. A range of standardised measures were used to assess verbal ability, mathematical processing, and spatial working memory alongside behavioural measures of spatial numerical associations. Experiment 12 provided evidence of aging and sex differences in different cognitive tasks and a marginal impact of embodiment on spatial-numerical processing; however the effect of embodiment was not supported in a larger more homogenous sample in Experiment 13. Chapter 6 reflects on the current findings and provides contextual information on how they align with previous research, outlining how evidence from the thesis extend current research paradigms and provides new evidence regarding the maintenance of spatial-numerical associations in healthy aging. Methodologies developed in the thesis are considered with relation to how they may be applied to assess individual differences in early number acquisition in children. Finally the discussion outlines methods and controversies within the field of numerical cognition, with consideration of new methods for measuring the strength of spatial-numerical associations (Pinhas, Tzelgov, & Ganor-Stern, 2012), alongside the potential application of modelling techniques to investigate individual differences in task performance.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Numerical analysis