Recent studies have been done to create models that predict the response of the human visual system (HVS) based on how the HVS processes an image. The most widely known of these models is the Gabor model, since the Gabor patterns closely resemble the receptive filters in the human eye. The work of this thesis examines the use of Symlets to represent the HVS, since Symlets provide the benefit of orthogonality. One major problem with Symlets is that the energy is not stable in respective Symlet channels when the image patterns are translated spatially. This thesis addresses this problem by up sampling Symlets instead of down sampling, and thus creating shift invariant Symlets. This thesis then compares the representation of Gabor versus Symlet approach in predicting the response of the HVS to detecting print defect patterns such as banding and graining. In summary we noticed that Symlet prediction outperforms the Gabor prediction thus Symlets would be a good choice for HVS response prediction. We also concluded that for banding defect periodicity and size are important factors that affect the response of the HVS to the patterns. For graining defects we noticed that size does not greatly affect the response of the HVS to the defect patterns. We introduced our results using two set of performance metrics, the mean and median.

Although most people have experienced word-finding difficulty at one time or another, there are no clinical instruments able to reliably distinguish normal age-related effects from pathology in word-finding impairment. Two experiments were conducted to establish a modified version of the Boston Naming Test (BNT) that includes latency times, the Boston Naming Test of Latencies (BNT-L), in order to improve the instrument's sensitivity to mild to moderate word-finding impairment. Experiment 1: Latency times on the 60-item BNT (Goodglass et al., 2001) for 235 healthy adults' ages 18-89 years were collected on a representative sample. Qualitative features of the BNT items, statistical analyses, IRT, and demographic considerations of age, gender, education, vocabulary, race and culture, helped create a reduced BNT-L version with 15 of the most discriminating items. Statistically sound and sophisticated normative tables are provided that adjust for unseen covariates. Response latencies did not indicate earlier age-related decline in an optimally healthy sample. Experiment 2: Twenty-three patients referred for neuropsychological testing were administered the BNT-L. Patients referred for evaluation of mild cognitive impairment or possible dementia produced significantly different response BNT-L latencies from the healthy sample whereas patients referred for mild brain injury evaluation did not. Normal word-finding problems were discussed in terms of serial stage models of lexical access, as well as in terms of automatic and controlled cognitive processes in younger and older adults. Statistical process for creating a psychometric instrument using latencies is illustrated.

Thesis Assessment and Development of Visual Perception in Preschool Children responds to the need of broader selection of standardized tools designed for the assessment of actual development of visual perception in preschool children, especially in relation to the assessment of school readiness. The main aim of the thesis is standardization of a new assessment tool. Complementary aim is also to design and evaluate a new intervention program supporting development of selected areas of visual perception for children before and at the beginning of their school attendance. In its theoretical part thesis scrutinizes current findings in the area of visual perception and its relation to basic academic skills, especially reading. The explorative part of thesis presents standardization study based on classical model of Test theory consisting of convergent validity and reliability evaluation of proposed test and setting national norms for four age groups (from 5 to 7 years). Normative group covered 1234 participants.

The 7 Graphology Factors Scale is standardised for application in industry. A literature study based on the personality theories of Freud, Jung, Murray and Cattell precedes the empirical research. Graphology is conceptualised, relevant existing graphology models are explored and a graphology theory and method for use in industry proposes that graphology should be regulated and applications classified on the same basis as psychometric tests. The empirical research is based on a sample comprising 360 subjects, stratified according to gender, position and language. The written protocol is subject to analysis of 59 characteristics on the basis of the configuration of the writing. language is irrelevant and the presentation of an intervening stimulus is avoided. Factor analysis results in eight secondary factors. These are I Task Orientation - Directive, II Task Orientation- Conscientious, Ill Emotional Stability, IV Extroversion, V Independence, VI Conceptualisation, VII Openness to Experience and VIII Need for Power. Cronbach's alpha coefficient achieves 0, 61 for Factor I. Stepwise regression analysis provides correlations between factors of the Thematic Apperception, Structured Objective Rorschach and 16 Personality Factor tests with all but Factor Ill, which is hypothesised to be a new construct. Five of the factors are hypothesised to align with the Big Five Personality Model. Thr9e-way analysis of variance, t-tests and the Mantei-Haenszel tests are applied to establish differentiation based on the stratification criteria. Norm tables based on Indigenous, English and Afrikaans first language groups are provided in stens and bands. Conclusions are that graphology has a worthy theoretical heritage and offers benefits to the psychological profession and specifically industry, as part of an assessment strategy. limitations are outlined and recommendations are made for further research. / Industrial and Organisational Psychology / D.Litt. et Phil. (Industrial Psychology)

The 7 Graphology Factors Scale is standardised for application in industry. A literature study based on the personality theories of Freud, Jung, Murray and Cattell precedes the empirical research. Graphology is conceptualised, relevant existing graphology models are explored and a graphology theory and method for use in industry proposes that graphology should be regulated and applications classified on the same basis as psychometric tests. The empirical research is based on a sample comprising 360 subjects, stratified according to gender, position and language. The written protocol is subject to analysis of 59 characteristics on the basis of the configuration of the writing. language is irrelevant and the presentation of an intervening stimulus is avoided. Factor analysis results in eight secondary factors. These are I Task Orientation - Directive, II Task Orientation- Conscientious, Ill Emotional Stability, IV Extroversion, V Independence, VI Conceptualisation, VII Openness to Experience and VIII Need for Power. Cronbach's alpha coefficient achieves 0, 61 for Factor I. Stepwise regression analysis provides correlations between factors of the Thematic Apperception, Structured Objective Rorschach and 16 Personality Factor tests with all but Factor Ill, which is hypothesised to be a new construct. Five of the factors are hypothesised to align with the Big Five Personality Model. Thr9e-way analysis of variance, t-tests and the Mantei-Haenszel tests are applied to establish differentiation based on the stratification criteria. Norm tables based on Indigenous, English and Afrikaans first language groups are provided in stens and bands. Conclusions are that graphology has a worthy theoretical heritage and offers benefits to the psychological profession and specifically industry, as part of an assessment strategy. limitations are outlined and recommendations are made for further research. / Industrial and Organisational Psychology / D.Litt. et Phil. (Industrial Psychology)

Magister Psychologiae - MPsych / Substance abuse is recognised as one of the greatest health and social problems in South Africa (SA). There is a need to explore the problem of substance use in the South African context in terms of the Bio-ecological Systems Theoretical Framework. All of the reviewed local and international studies on instruments that are used to measure factors associated with adolescent substance use, while yielding useful information; do not adequately address the issues of an instrument that successfully includes all the levels of the Bio-ecological Systems Theoretical Framework at the dimension level. As a result, a need for an applicable instrument exists. The overall purpose of the current study was to evaluate the content validity of the dimensions of the proposed self-administered questionnaire in terms of the Bio-ecological Systems Theoretical Framework, which will assist the factors associated with youth at risk of substance abuse in low socio economic status communities in the South African context. The study was framed in psychometric test theory focusing specifically on the procedures for content validation. It is being increasingly recognized that the development of a valid test requires multiple procedures, which are employed sequentially, at different stages of test construction. Validity is thus built into the test development from the outset. Participants were selected by means of purposive sampling. The sampling method was appropriate since the participants were required to meet certain inclusive criteria. The participants comprised of two groups of community leaders within two different communities on the Cape Flats. An adapted version of the Nominal Group Technique method was employed to collect data. The data for aim one was collected using a self administered questionnaire (Content Validity Questionnaire) consisting of two sections. The first section was presented in the form of a ranking scale with all relevant factors associated with adolescent substance use. The second section of part 1 was in the form of open-ended questions. The second aim was collected in the form of focus groups. Data was analysed quantitatively and qualitatively in the relevant sections. Data collected from the Content Validity Questionnaire (CVQ) was analysed quantitatively by means of statistical analysis making use of frequencies, and the open-ended questions of the content validity and data from the focus groups was analysed qualitatively by means of thematic analysis. The study concluded that all factors presented in the CVQ are important factors associated with adolescent substance use in the two low socio-economic statuses communities that were analysed in both the quantitative and qualitative components of the study.

Recent political and social changes in South Africa have created the need for culture-fair tests for cross-cultural measurement of cognitive ability. This need has been highlighted by the professional, legal and research communities. For cognitive assessment, dynamic assessment is more equitable because it involves a test-train-retest procedure, which shows what performance levels individuals are able to attain when relevant training is provided. Following Binet’s thinking, dynamic assessment aims to identify those individuals who are likely to benefit from additional training. The theoretical basis for learning potential assessment is Vygotsky’s concept of the zone of proximal development. This thesis describes the development, standardisation and evaluation of the Learning Potential Computerised Adaptive Test (LPCAT), for measuring learning potential in the culturally diverse South African population by means of nonverbal figural items. In accordance with Vygotsky’s view, learning potential is defined as a combination of present performance and the extent to which performance is increased after relevant training. This definition allows for comparison of individuals at different levels of initial performance and with different measures of improvement. Computerised adaptive testing based on item response theory, as used in the LPCAT, is uniquely suitable for increasing both measurement accuracy and testing efficiency of dynamic testing, two aspects that have been identified as problematic. The LPCAT pretest and the post-test are two separate adaptive tests, hence eliminating the role of memory in post-test performance. Several multicultural groups were used for item analysis and test validation. The results support the LPCAT as a culture-fair measure of learning potential in the nonverbal general reasoning domain. For examinees with a wide range of ability levels, LPCAT scores correlate strongly with academic performance. For African examinees, poor proficiency in English (the language of teaching) hampers academic performance. The LPCAT ensures the equitable measurement of learning potential, independent of language proficiency and prior scholastic learning and can be used to help select candidates for further training or developmental opportunities. / Psychology / D. Litt. et Phil. (Psychology)

The changing nature of work and its competitive characteristics are global phenomena and are mainly fuelled by ongoing technological advancement. This creates unique challenges for talent attraction and the retention of high performing individuals. In addition, the global workforce is becoming more diverse due to demographic, societal and cultural changes and companies are placing greater demands on employee competency and performance. Managing the human factor as a strategic asset in organisations remains a primary challenge in securing a competitive advantage. The road construction industry in South Africa is no different. There is growing competition between civil engineering contractors to secure tenders and to maximise profitability. This is only possible with a sufficient and sustainable labour force. Valid selection processes are therefore required to ensure that the most productive individuals are selected for the most suitable jobs. Reliable and valid performance predictors will assist employers in making appropriate selection decisions. Selecting high performing individuals will support and enhance overall organisational performance. ix In this study the investigation focused on whether psychomotor ability and learning potential are statistically significant predictors of work performance - with specific reference to drivers and machine operators in a road construction company. A quantitative approach was followed to investigate the relationships between variables, or then the prediction of one dependent variable (driver and machine operator performance) by means of two independent variables (psychomotor ability and learning potential). Results from the study did not indicate any statistically significant relationships between the variables. Only scientifically validated assessment instruments were used in the study - which means the findings led to a renewed focus on the importance of performance measurement and the psychometric quality (reliability and validity) of performance data. / Industrial and Organisational Psychology / M.A. (Industrial and Organisational Psychology)

Recent political and social changes in South Africa have created the need for culture-fair tests for cross-cultural measurement of cognitive ability. This need has been highlighted by the professional, legal and research communities. For cognitive assessment, dynamic assessment is more equitable because it involves a test-train-retest procedure, which shows what performance levels individuals are able to attain when relevant training is provided. Following Binet’s thinking, dynamic assessment aims to identify those individuals who are likely to benefit from additional training. The theoretical basis for learning potential assessment is Vygotsky’s concept of the zone of proximal development. This thesis describes the development, standardisation and evaluation of the Learning Potential Computerised Adaptive Test (LPCAT), for measuring learning potential in the culturally diverse South African population by means of nonverbal figural items. In accordance with Vygotsky’s view, learning potential is defined as a combination of present performance and the extent to which performance is increased after relevant training. This definition allows for comparison of individuals at different levels of initial performance and with different measures of improvement. Computerised adaptive testing based on item response theory, as used in the LPCAT, is uniquely suitable for increasing both measurement accuracy and testing efficiency of dynamic testing, two aspects that have been identified as problematic. The LPCAT pretest and the post-test are two separate adaptive tests, hence eliminating the role of memory in post-test performance. Several multicultural groups were used for item analysis and test validation. The results support the LPCAT as a culture-fair measure of learning potential in the nonverbal general reasoning domain. For examinees with a wide range of ability levels, LPCAT scores correlate strongly with academic performance. For African examinees, poor proficiency in English (the language of teaching) hampers academic performance. The LPCAT ensures the equitable measurement of learning potential, independent of language proficiency and prior scholastic learning and can be used to help select candidates for further training or developmental opportunities. / Psychology / D. Litt. et Phil. (Psychology)

The changing nature of work and its competitive characteristics are global phenomena and are mainly fuelled by ongoing technological advancement. This creates unique challenges for talent attraction and the retention of high performing individuals. In addition, the global workforce is becoming more diverse due to demographic, societal and cultural changes and companies are placing greater demands on employee competency and performance. Managing the human factor as a strategic asset in organisations remains a primary challenge in securing a competitive advantage. The road construction industry in South Africa is no different. There is growing competition between civil engineering contractors to secure tenders and to maximise profitability. This is only possible with a sufficient and sustainable labour force. Valid selection processes are therefore required to ensure that the most productive individuals are selected for the most suitable jobs. Reliable and valid performance predictors will assist employers in making appropriate selection decisions. Selecting high performing individuals will support and enhance overall organisational performance. ix In this study the investigation focused on whether psychomotor ability and learning potential are statistically significant predictors of work performance - with specific reference to drivers and machine operators in a road construction company. A quantitative approach was followed to investigate the relationships between variables, or then the prediction of one dependent variable (driver and machine operator performance) by means of two independent variables (psychomotor ability and learning potential). Results from the study did not indicate any statistically significant relationships between the variables. Only scientifically validated assessment instruments were used in the study - which means the findings led to a renewed focus on the importance of performance measurement and the psychometric quality (reliability and validity) of performance data. / Industrial and Organisational Psychology / M.A. (Industrial and Organisational Psychology)