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    Mapping the mind with broken theodolites : contributions to multidimensional scaling methodology, with special application to triadic data, and the sorting and hierarchical sorting methods : a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Human Development Studies at Massey University
    (Massey University, 1995) Bimler, D L
    This thesis focuses on the psychological applications of Multidimensional Scaling (MDS) theory and methodology. The results are investigated of treating certain kinds of dissimilarity data (triadic data, to begin with) as comparisons between dissimilarities. This is a familiar idea but many of its implications are unexplored. First, when data are available from more than one subject, it becomes possible to apply models of individual variation, in non-metric form. The Weighted Euclidean (or INDSCAL) model is the one used most often in this thesis, but the more general IDIOSCAL model is used to investigate individual differences in the case of colour vision. The data sets need not be complete. This is important when the size of the stimulus set means that there are too many comparisons for a single subject to respond to them all. Second, Maximum Likelihood Estimation (MLE) becomes a straightforward generalisation of the standard hill-descent algorithm for minimising Stress. Third, data collected with the sorting and hierarchical sorting methods can also be regarded as dissimilarity comparisons. The convenience of the sorting method and the lesser demands it makes on subjects when the number of stimuli is large have led to its widespread use, but the best way of analysing such data is uncertain. A 'reconstructed dyad' analysis is described and shown to be better than the usual co-occurence approach in a number of examples in which evidence about the true perceptual or conceptual space is available independently. Finally, when the data are interpreted as dissimilarity comparisons, an interactive method of scaling large stimulus sets becomes possible, in which one selectively acquires incomplete data, concentrating on comparisons which are expected to contain most information about the configuration. This approach has been applied twice, with the stimuli being simple synthesised sounds in one example, and complex natural sounds (canine heartbeats) in the second, working well in both cases. The potential applications for training people to recognise sounds are briefly considered. Some possibilities for future research arising from this work are described.
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    Colour space distortions in patients with type 2 diabetes mellitus
    (Cambridge University Press, 2006) Feitosa Santana C; Oiwa NN; Paramel GV; Bimler D; Costa MF; Lago M; Nishi M; Ventura DF
    Color vision impairment was examined in patients with type 2 diabetes mellitus (DM2) without retinopathy. We assessed the type and degree of distortions of individual color spaces. DM2 patients (n = 32), and age-matched controls (n = 20) were tested using the Farnsworth D-15 and the Lanthony D-15d tests. In addition, subsets of caps from both tests were employed in a triadic procedure (Bimler & Kirkland, 2004). Matrices of inter-cap subjective dissimilarities were estimated from each subject's 'odd-one-out' choices, and processed using non-metric multidimensional scaling. Two-dimensional color spaces, individual and group (DM2 patients; controls), were reconstructed, with the axes interpreted as the R/G and B/Y perceptual opponent systems. Compared to controls, patient results were not significant for the D-15 and D-15d. In contrast, in the triadic procedure the residual distances were significantly different compared to controls: right eye, P = 0.021, and left eye, P =0.022. Color space configurations for the DM2 patients were compressed along the B/Y and R/G dimensions. The present findings agree with earlier studies demonstrating diffuse losses in early stages of DM2. The proposed method of testing uses color spaces to represent discrimination and provides more differentiated quantitative diagnosis, which may be interpreted as the perceptual color system affected. In addition, it enables the detection of very mild color vision impairment that is not captured by the D-15d test. Along with fundoscopy, individual color spaces may serve for monitoring early functional changes and thereby to support a treatment strategy.
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    Multidimensional scaling of D15 caps: color-vision defects among tobacco smokers?
    (CAMBRIDGE UNIV PRESS, 2004) Bimler D; Kirkland J
    Tobacco smoke contains a range of toxins including carbon monoxide and cyanide. With specialized cells and high metabolic demands, the optic nerve and retina are vulnerable to toxic exposure. We examined the possible effects of smoking on color vision: specifically, whether smokers perceive a different pattern of suprathreshold color dissimilarities from nonsmokers. It is already known that smokers differ in threshold color discrimination, with elevated scores on the Roth 28-Hue Desaturated panel test. Groups of smokers and nonsmokers, matched for sex and age, followed a triadic procedure to compare dissimilarities among 32 pigmented stimuli (the caps of the saturated and desaturated versions of the D15 panel test). Multidimensional scaling was applied to quantify individual variations in the salience of the axes of color space. Despite the briefness, simplicity, and "low-tech" nature of the procedure, subtle but statistically significant differences did emerge: on average the smoking group were significantly less sensitive to red-green differences. This is consistent with some form of injury to the optic nerve.