Reproductive conflicts in honeybee colonies
- Pirk, Christian Walter Werner
- Authors: Pirk, Christian Walter Werner
- Date: 2002
- Subjects: Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5755 , http://hdl.handle.net/10962/d1005443
- Description: In advanced eusocial hymenopteran societies workers have ovaries and can lay eggs, but are unable to mate. Workers are more related to their own offspring than to every other member of the colony. So worker reproduction contains both worker-worker and worker-queen conflict. The queen- worker conflict is discussed elsewhere, but if the queen mates with more than two males, worker policing should be selected to lower potential conflicts. However in the Cape honeybee it was predicted that worker policing is absent or less expressed than in other honeybee subspecies, because workers produce female offspring thelytokously. So laying workers and their offspring are nearly genetically identical, which results in the fact that other workers are as related to workers derived from eggs laid by the queen as laid by a worker. However, worker reproduction may be costly and therefore worker policing could be an evolutionary adaptation in the Cape honeybee to lower the costs derived from laying worker activity. Indeed, Cape honeybee colonies show efficient egg removal behaviour, suggesting that other factors like colony efficiency could favour egg removal behaviour. Since egg removal behaviour is a colony phenomenon, factors that affect colony performance could also affect egg removal behaviour. Egg removal behaviour was considerably affected by environmental changes, indicating that other tasks have a higher priority than egg removal behaviour. Thousands of queenright colonies of the neighbouring subspecies (A. m. scutellata) were taken over by laying A. m. capensis workers, showing that A. m. capensis workers are facultative social parasites. These observations strongly indicate that laying workers of A. m. capensis are able to evade worker policing and the inhibitory effects of the queen pheromones, but what potential strategies could these laying workers use to increase the survival of their eggs and evade the queen? On the one hand, egg removal behaviour is variable. One behavioural strategy of laying workers to achieve successful reproduction could be that they lay during periods with low egg removal behaviour. On the other hand, the inhibitory effect of the queen’s pheromones diminishes with distance. Maybe the level of egg removal also depends, like the inhibitory effect of the queen pheromones, on the distance from the queen. Indeed, further away from the queen the effect of the queen pheromone and the level of egg removal is reduced, making successful worker reproduction possible. In both subspecies, A. m. capensis and A. m. scutellata, egg removal behaviour is reduced further away from the queen. In the case of A. m. scutellata egg removal is lacking further away from the queen. This explains why colonies of scutellata are so prone to takeovers by laying Cape honeybee workers. One question in the context of parasitic Cape honeybees is how they manage to get into the host colony. One way could be that they get into the colonies during a natural colony merger which is common in African bees. Two unrelated colonies merged and it took them only 24 hours to show effective integration. Because both colonies are unrelated, the potential reproductive conflict among workers should be more strongly expressed than in a normal colony, which is not the result of a merger. Therefore, the effect of nestmate recognition for eggs on the egg removal behaviour was investigated. The results suggest that workers recognise the origin of an egg and that the standard policing experiments overestimate the level of egg removal and only represent relative values. Moreover, the results show that colony specific components on the eggs are more important than a postulated queen egg marking pheromone. Finally, for the first time empirical evidence from a population of the parasitic laying Cape honeybee workers, invading thousands of colonies of A. m. scutellata in northern South Africa, for a short-sighted selection theory is presented.
- Full Text:
- Date Issued: 2002
- Authors: Pirk, Christian Walter Werner
- Date: 2002
- Subjects: Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5755 , http://hdl.handle.net/10962/d1005443
- Description: In advanced eusocial hymenopteran societies workers have ovaries and can lay eggs, but are unable to mate. Workers are more related to their own offspring than to every other member of the colony. So worker reproduction contains both worker-worker and worker-queen conflict. The queen- worker conflict is discussed elsewhere, but if the queen mates with more than two males, worker policing should be selected to lower potential conflicts. However in the Cape honeybee it was predicted that worker policing is absent or less expressed than in other honeybee subspecies, because workers produce female offspring thelytokously. So laying workers and their offspring are nearly genetically identical, which results in the fact that other workers are as related to workers derived from eggs laid by the queen as laid by a worker. However, worker reproduction may be costly and therefore worker policing could be an evolutionary adaptation in the Cape honeybee to lower the costs derived from laying worker activity. Indeed, Cape honeybee colonies show efficient egg removal behaviour, suggesting that other factors like colony efficiency could favour egg removal behaviour. Since egg removal behaviour is a colony phenomenon, factors that affect colony performance could also affect egg removal behaviour. Egg removal behaviour was considerably affected by environmental changes, indicating that other tasks have a higher priority than egg removal behaviour. Thousands of queenright colonies of the neighbouring subspecies (A. m. scutellata) were taken over by laying A. m. capensis workers, showing that A. m. capensis workers are facultative social parasites. These observations strongly indicate that laying workers of A. m. capensis are able to evade worker policing and the inhibitory effects of the queen pheromones, but what potential strategies could these laying workers use to increase the survival of their eggs and evade the queen? On the one hand, egg removal behaviour is variable. One behavioural strategy of laying workers to achieve successful reproduction could be that they lay during periods with low egg removal behaviour. On the other hand, the inhibitory effect of the queen’s pheromones diminishes with distance. Maybe the level of egg removal also depends, like the inhibitory effect of the queen pheromones, on the distance from the queen. Indeed, further away from the queen the effect of the queen pheromone and the level of egg removal is reduced, making successful worker reproduction possible. In both subspecies, A. m. capensis and A. m. scutellata, egg removal behaviour is reduced further away from the queen. In the case of A. m. scutellata egg removal is lacking further away from the queen. This explains why colonies of scutellata are so prone to takeovers by laying Cape honeybee workers. One question in the context of parasitic Cape honeybees is how they manage to get into the host colony. One way could be that they get into the colonies during a natural colony merger which is common in African bees. Two unrelated colonies merged and it took them only 24 hours to show effective integration. Because both colonies are unrelated, the potential reproductive conflict among workers should be more strongly expressed than in a normal colony, which is not the result of a merger. Therefore, the effect of nestmate recognition for eggs on the egg removal behaviour was investigated. The results suggest that workers recognise the origin of an egg and that the standard policing experiments overestimate the level of egg removal and only represent relative values. Moreover, the results show that colony specific components on the eggs are more important than a postulated queen egg marking pheromone. Finally, for the first time empirical evidence from a population of the parasitic laying Cape honeybee workers, invading thousands of colonies of A. m. scutellata in northern South Africa, for a short-sighted selection theory is presented.
- Full Text:
- Date Issued: 2002
Brood cycles in queenless colonies of Apis mellifera capensis
- Authors: Crous, Kendall Lauren
- Date: 2010
- Subjects: Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5652 , http://hdl.handle.net/10962/d1005335 , Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Description: In a honeybee colony, the loss of a queen is considered to be a serious occurrence and, if a new queen is not produced, ultimately doomed. However, in colonies of Apis mellifera capensis (Cape honeybees), numerous pathways are available for a colony which unexpectedly losses a queen. At the onset of this experiment, four colonies of A. m. capensis were dequeened. Following this photographs of all brood frames in each colony were taken and the contents of the cells analysed. Cells were chosen at random but once selected were repeatedly analysed for the duration of the experiment. The contents of a total of 44 888 individual cells were analysed. Any queen cells constructed during the sampling period were removed, maintaining a queenless state. In each colony, as predicted, the removal of the queen evoked a variety of responses in an attempt to rectify the sudden loss. However, ultimately three of the four colonies absconded, leaving little by way of stores. Three of the four colonies initially attempted to rear a new queen while one colony was immediately invaded by a presumed foreign queen and hence any attempt at queen cell construction ceased. An increased number of queen cells in the swarm position were recorded in all colonies. The invasion of a colony by a foreign queen was considered to be a new pathway available for queenless colonies of A.m capensis. Worker policing and suspected brood cannibalism was prevalent in all sampled colonies yet in addition, the transfer of eggs and larvae from cell to cell was also observed which may have increased the suspected cases of policing and cannibalism. It was unclear whether an egg or larva had been consumed or simply moved to another cell on the brood frame. All colonies contained eggs from laying workers to varying degrees, based on the length of each individual sampling period which varied between colonies due to differences in absconding dates. A steady breakdown in the effectiveness of the division of labour amongst the worker bees was observed in each of the colonies highlighting the vital role of a queen. This breakdown was clearly seen in the reduction in general housekeeping within a colony. An increase in stores indicated a possible increase in the number of forager bees, thereby reducing the number of worker bees available for other duties. Pathways available to broodright colonies and strategies used following sudden queen loss are discussed.
- Full Text:
- Date Issued: 2010
- Authors: Crous, Kendall Lauren
- Date: 2010
- Subjects: Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5652 , http://hdl.handle.net/10962/d1005335 , Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Description: In a honeybee colony, the loss of a queen is considered to be a serious occurrence and, if a new queen is not produced, ultimately doomed. However, in colonies of Apis mellifera capensis (Cape honeybees), numerous pathways are available for a colony which unexpectedly losses a queen. At the onset of this experiment, four colonies of A. m. capensis were dequeened. Following this photographs of all brood frames in each colony were taken and the contents of the cells analysed. Cells were chosen at random but once selected were repeatedly analysed for the duration of the experiment. The contents of a total of 44 888 individual cells were analysed. Any queen cells constructed during the sampling period were removed, maintaining a queenless state. In each colony, as predicted, the removal of the queen evoked a variety of responses in an attempt to rectify the sudden loss. However, ultimately three of the four colonies absconded, leaving little by way of stores. Three of the four colonies initially attempted to rear a new queen while one colony was immediately invaded by a presumed foreign queen and hence any attempt at queen cell construction ceased. An increased number of queen cells in the swarm position were recorded in all colonies. The invasion of a colony by a foreign queen was considered to be a new pathway available for queenless colonies of A.m capensis. Worker policing and suspected brood cannibalism was prevalent in all sampled colonies yet in addition, the transfer of eggs and larvae from cell to cell was also observed which may have increased the suspected cases of policing and cannibalism. It was unclear whether an egg or larva had been consumed or simply moved to another cell on the brood frame. All colonies contained eggs from laying workers to varying degrees, based on the length of each individual sampling period which varied between colonies due to differences in absconding dates. A steady breakdown in the effectiveness of the division of labour amongst the worker bees was observed in each of the colonies highlighting the vital role of a queen. This breakdown was clearly seen in the reduction in general housekeeping within a colony. An increase in stores indicated a possible increase in the number of forager bees, thereby reducing the number of worker bees available for other duties. Pathways available to broodright colonies and strategies used following sudden queen loss are discussed.
- Full Text:
- Date Issued: 2010
"I felt that I deserved it" : an Investigation into HIV-related PTSD, traumatic life events, and the personal experiences of living with HIV : a mixed-method study
- Authors: Boulind, Melissa Jane
- Date: 2014
- Subjects: Post-traumatic stress disorder -- Psychological aspects -- Research -- South Africa -- Kwazulu HIV infections -- Psychological aspects -- Research -- South Africa -- Kwazulu HIV-positive persons -- South Africa -- Kwazulu -- Interviews Psychic trauma -- Research Stress (Psychology) -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3211 , http://hdl.handle.net/10962/d1012172
- Description: There appears to be a growing body of literature focusing on PTSD and HIV-related PTSD (the diagnosis of HIV being the significant traumatic event) amongst HIV-positive samples, but only a few African studies that attempt to estimate the prevalence of PTSD amongst HIV-positive people, and even fewer that attempt to estimate the prevalence of HIV-related PTSD. The systemic review presented in this study is currently fully inclusive and is the most up-to-date available. Estimates of the prevalence of PTSD and HIV-related PTSD in South Africa range from 0.7 to 54.1% and, 4.2 to 40% respectively. The current cross-sectional study made use of a mixed-method approach to investigate traumatic life events, PTSD and HIV-related PTSD within a primary health-care centre in KwaZulu-Natal. The quantitative sample consisted of 159 adults (18-50 years) who were compliant on ARV medication. Using the CIDI-PTSD module, the adapted CIDI-PTSD module for HIV, and IES-R, findings indicated that 62% had reported some kind of traumatic event in their lifetime, with 29.6% of participants meeting the criteria for lifetime PTSD, and 40.9% meeting the criteria for lifetime HIV-related PTSD. Altogether, 57.9% of individuals met the criteria for some form of PTSD (either regular PTSD or HIV-related PTSD), and 12.6% met the criteria for both PTSD and HIV-related PTSD. Of the different categories of traumatic events, interpersonal violence has the highest rate of PTSD, followed by a diagnosis of and living with HIV, and then disaster. Furthermore, the IES-R was compared for its usefulness as a screening measure for PTSD against both the CIDI, but results suggest that it is an inferior screening measure to the PDS. The qualitative study consisted of six participants who were examined using IPA methodology informed by the Ehlers and Clark (2000) Model of trauma. Their experiences revealed experiences of stigma, a number of negative appraisals, negative emotions and coping behaviours. Some of the latter might serve as compensatory mechanisms to avoid negative judgements. Hypervigilance seems to be a feature of ARV-compliance that might confer added vulnerability to PTSD and other anxiety disorders.
- Full Text:
- Date Issued: 2014
- Authors: Boulind, Melissa Jane
- Date: 2014
- Subjects: Post-traumatic stress disorder -- Psychological aspects -- Research -- South Africa -- Kwazulu HIV infections -- Psychological aspects -- Research -- South Africa -- Kwazulu HIV-positive persons -- South Africa -- Kwazulu -- Interviews Psychic trauma -- Research Stress (Psychology) -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3211 , http://hdl.handle.net/10962/d1012172
- Description: There appears to be a growing body of literature focusing on PTSD and HIV-related PTSD (the diagnosis of HIV being the significant traumatic event) amongst HIV-positive samples, but only a few African studies that attempt to estimate the prevalence of PTSD amongst HIV-positive people, and even fewer that attempt to estimate the prevalence of HIV-related PTSD. The systemic review presented in this study is currently fully inclusive and is the most up-to-date available. Estimates of the prevalence of PTSD and HIV-related PTSD in South Africa range from 0.7 to 54.1% and, 4.2 to 40% respectively. The current cross-sectional study made use of a mixed-method approach to investigate traumatic life events, PTSD and HIV-related PTSD within a primary health-care centre in KwaZulu-Natal. The quantitative sample consisted of 159 adults (18-50 years) who were compliant on ARV medication. Using the CIDI-PTSD module, the adapted CIDI-PTSD module for HIV, and IES-R, findings indicated that 62% had reported some kind of traumatic event in their lifetime, with 29.6% of participants meeting the criteria for lifetime PTSD, and 40.9% meeting the criteria for lifetime HIV-related PTSD. Altogether, 57.9% of individuals met the criteria for some form of PTSD (either regular PTSD or HIV-related PTSD), and 12.6% met the criteria for both PTSD and HIV-related PTSD. Of the different categories of traumatic events, interpersonal violence has the highest rate of PTSD, followed by a diagnosis of and living with HIV, and then disaster. Furthermore, the IES-R was compared for its usefulness as a screening measure for PTSD against both the CIDI, but results suggest that it is an inferior screening measure to the PDS. The qualitative study consisted of six participants who were examined using IPA methodology informed by the Ehlers and Clark (2000) Model of trauma. Their experiences revealed experiences of stigma, a number of negative appraisals, negative emotions and coping behaviours. Some of the latter might serve as compensatory mechanisms to avoid negative judgements. Hypervigilance seems to be a feature of ARV-compliance that might confer added vulnerability to PTSD and other anxiety disorders.
- Full Text:
- Date Issued: 2014
Heads and tales: the effect of mild head injuries of rugby players: cognitive deficit and postconcussive symptoms
- Authors: Border, Michael Anthony
- Date: 2001
- Subjects: Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2937 , http://hdl.handle.net/10962/d1002446 , Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Description: This study investigated the cumulative effect of mild head injuries on rugby players. A comprehensive battery of neuropsychological tests was administered and subjects completed a self-report postconcussive symptom questionnaire. Data were collected for the two rugby groups, Springbok rugby players (n = 26) and Under 21 rugby players (n = 19), and for the control group, national hockey players (n = 21). Group comparisons of the percentage of individuals with deficit or self-reported symptomatology were made between: (i) the contact sport groups and the control group; (ii) the forwards and the backs within each rugby group and the rugby forwards and the control group; and (iii) the Springbok and Under 21 rugby players. Broadly speaking, comparative results on the neuropsychological tests and the self-reported postconcussive symptoms clearly distinguished between contact sport players and non-contact sport players and indicated the presence of diffuse brain damage in the contact sport players. There was also clear evidence of positional variation within the rugby groups, with the forwards (more full contact positions) most susceptible to impairment. Neuropsychological test results revealed deficit in information processing speed, attention and concentration, mental flexibility, visual memory and verbal new learning. The most significant neuropsychiatric complaints were reported in the areas of memory, social contact, sensitivity to noise, lowered frustration tolerance, anxiety and worry, and depression. The most sensitive neuropsychological test used in the present study was the Digit Symbol Substitution test. This test clearly distinguished contact sport players from non-contact sport players, and forwards from backs.
- Full Text:
- Date Issued: 2001
- Authors: Border, Michael Anthony
- Date: 2001
- Subjects: Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2937 , http://hdl.handle.net/10962/d1002446 , Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Description: This study investigated the cumulative effect of mild head injuries on rugby players. A comprehensive battery of neuropsychological tests was administered and subjects completed a self-report postconcussive symptom questionnaire. Data were collected for the two rugby groups, Springbok rugby players (n = 26) and Under 21 rugby players (n = 19), and for the control group, national hockey players (n = 21). Group comparisons of the percentage of individuals with deficit or self-reported symptomatology were made between: (i) the contact sport groups and the control group; (ii) the forwards and the backs within each rugby group and the rugby forwards and the control group; and (iii) the Springbok and Under 21 rugby players. Broadly speaking, comparative results on the neuropsychological tests and the self-reported postconcussive symptoms clearly distinguished between contact sport players and non-contact sport players and indicated the presence of diffuse brain damage in the contact sport players. There was also clear evidence of positional variation within the rugby groups, with the forwards (more full contact positions) most susceptible to impairment. Neuropsychological test results revealed deficit in information processing speed, attention and concentration, mental flexibility, visual memory and verbal new learning. The most significant neuropsychiatric complaints were reported in the areas of memory, social contact, sensitivity to noise, lowered frustration tolerance, anxiety and worry, and depression. The most sensitive neuropsychological test used in the present study was the Digit Symbol Substitution test. This test clearly distinguished contact sport players from non-contact sport players, and forwards from backs.
- Full Text:
- Date Issued: 2001
Cardiovascular disease risk in Black African females and the efficacy of a walking programme on blood pressure in a sub-sample
- Authors: Crymble, Tegan
- Date: 2014
- Subjects: Cardiovascular system -- Diseases -- South Africa -- Eastern Cape , Women -- Health and hygiene -- South Africa -- Eastern Cape , Obesity -- South Africa -- Eastern Cape , Hypertension -- South Africa -- Eastern Cape , Walking -- South Africa -- Eastern Cape -- Physiological aspects , Lifestyles -- Health aspects -- South Africa -- Eastern Cape , Health attitudes -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5152 , http://hdl.handle.net/10962/d1013234
- Description: The purpose of the study was to investigate the cardiovascular disease (CVD) risk profile of black African females in the Makana region, Eastern Cape, South Africa. Baseline measures from 40 participants, who met the criteria, were compared against the 2003 South African Demographic and Health Survey (SADHS) and the 2013 South African National Health and Nutritional Examination Survey (SANHANES-1). The risk factors measured were anthropometric (stature, body mass and body mass index (BMI)), morphological (waist circumference (WC), fat mass and lean mass), cardiovascular (heart rate and blood pressure (BP)), physical activity (step count and energy expenditure), biochemical (glycated haemoglobin and full blood lipid profile) and behavioural (alcohol and tobacco use). Results showed significantly higher (p≤0.05) values for overweight/obesity (BMI 37.60 kg.m⁻²; WC 1130.58 mm; fat mass 45.23%) and high BP (130/88 mmHg) compared to the previous national surveys, highlighting these CVD risk factors as problematic. The subsequent sub-study aimed to assess the efficacy of a pedometer-based walking intervention on high BP. The walking programme (n=25) was based on individual step goals to be completed at a moderate-intensity on five days.week⁻¹ for 12 weeks. The same measurements were taken at monthly intervals, Week 0, Week 4, Week 8 and Week 12, with the addition of dietary intake and fitness level, and the exclusion of the behavioural variables. There were no significant differences (p≤0.05) in systolic and diastolic BP with the exercise intervention, although there was a strong, negative relationship with time for diastolic BP (r²=0.9857). This trend suggests that the lack of significance may be a result of poor compliance and/or the small sample size. Individual results, however, showed no compliance-result relationship for the two risk factors of interest: overweight/obesity and high BP. Future recommendations include supervised or group-based exercise interventions to improve compliance, and the addition of resistance training to the aerobic programme.
- Full Text:
- Date Issued: 2014
- Authors: Crymble, Tegan
- Date: 2014
- Subjects: Cardiovascular system -- Diseases -- South Africa -- Eastern Cape , Women -- Health and hygiene -- South Africa -- Eastern Cape , Obesity -- South Africa -- Eastern Cape , Hypertension -- South Africa -- Eastern Cape , Walking -- South Africa -- Eastern Cape -- Physiological aspects , Lifestyles -- Health aspects -- South Africa -- Eastern Cape , Health attitudes -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5152 , http://hdl.handle.net/10962/d1013234
- Description: The purpose of the study was to investigate the cardiovascular disease (CVD) risk profile of black African females in the Makana region, Eastern Cape, South Africa. Baseline measures from 40 participants, who met the criteria, were compared against the 2003 South African Demographic and Health Survey (SADHS) and the 2013 South African National Health and Nutritional Examination Survey (SANHANES-1). The risk factors measured were anthropometric (stature, body mass and body mass index (BMI)), morphological (waist circumference (WC), fat mass and lean mass), cardiovascular (heart rate and blood pressure (BP)), physical activity (step count and energy expenditure), biochemical (glycated haemoglobin and full blood lipid profile) and behavioural (alcohol and tobacco use). Results showed significantly higher (p≤0.05) values for overweight/obesity (BMI 37.60 kg.m⁻²; WC 1130.58 mm; fat mass 45.23%) and high BP (130/88 mmHg) compared to the previous national surveys, highlighting these CVD risk factors as problematic. The subsequent sub-study aimed to assess the efficacy of a pedometer-based walking intervention on high BP. The walking programme (n=25) was based on individual step goals to be completed at a moderate-intensity on five days.week⁻¹ for 12 weeks. The same measurements were taken at monthly intervals, Week 0, Week 4, Week 8 and Week 12, with the addition of dietary intake and fitness level, and the exclusion of the behavioural variables. There were no significant differences (p≤0.05) in systolic and diastolic BP with the exercise intervention, although there was a strong, negative relationship with time for diastolic BP (r²=0.9857). This trend suggests that the lack of significance may be a result of poor compliance and/or the small sample size. Individual results, however, showed no compliance-result relationship for the two risk factors of interest: overweight/obesity and high BP. Future recommendations include supervised or group-based exercise interventions to improve compliance, and the addition of resistance training to the aerobic programme.
- Full Text:
- Date Issued: 2014
Lag length selection for vector error correction models
- Authors: Sharp, Gary David
- Date: 2010
- Subjects: Akaike Information Criterion Mathematical models -- Evaluation Autoregression (Statistics) Error analysis (Mathematics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5568 , http://hdl.handle.net/10962/d1002808
- Description: This thesis investigates the problem of model identification in a Vector Autoregressive framework. The study reviews the existing research, conducts an extensive simulation based analysis of thirteen information theoretic criterion (IC), one of which is a novel derivation. The simulation exercise considers the evaluation of seven alternative error restricted vector autoregressive models with four different lag lengths. Alternative sample sizes and parameterisations are also evaluated and compared to results in the existing literature. The results of the comparative analysis provide strong support for the efficiency based criterion of Akaike and in particular the selection capability of the novel criterion, referred to as a modified corrected Akaike information criterion, demonstrates useful finite sample properties.
- Full Text:
- Date Issued: 2010
- Authors: Sharp, Gary David
- Date: 2010
- Subjects: Akaike Information Criterion Mathematical models -- Evaluation Autoregression (Statistics) Error analysis (Mathematics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5568 , http://hdl.handle.net/10962/d1002808
- Description: This thesis investigates the problem of model identification in a Vector Autoregressive framework. The study reviews the existing research, conducts an extensive simulation based analysis of thirteen information theoretic criterion (IC), one of which is a novel derivation. The simulation exercise considers the evaluation of seven alternative error restricted vector autoregressive models with four different lag lengths. Alternative sample sizes and parameterisations are also evaluated and compared to results in the existing literature. The results of the comparative analysis provide strong support for the efficiency based criterion of Akaike and in particular the selection capability of the novel criterion, referred to as a modified corrected Akaike information criterion, demonstrates useful finite sample properties.
- Full Text:
- Date Issued: 2010
An investigation of male and female cognitive ability on the WAIS-III
- Authors: Muirhead, Joanne
- Date: 2000
- Subjects: Wechsler Adult Intelligence Scale , Sex differences (Psychology) , Intelligence tests -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3028 , http://hdl.handle.net/10962/d1002537 , Wechsler Adult Intelligence Scale , Sex differences (Psychology) , Intelligence tests -- South Africa
- Description: This study, which formed part of a larger research project, investigated the effect of gender on test performance on the Wechsler Adult Intelligence Scale - Third Edition (WAIS-III). The WAIS-III was administered to a sample of 68 participants in the Eastern Cape following the initiative of the Human Sciences Research Council to standardise the WAIS-III for a South African population. The participants, aged 19 to 30, were stratified according to language of origin (African or English First Language), educational attainment (matriculant or graduate), quality of education (Department of Education and Training or private/"Model C" school) and gender. Analyses of variance and two sample t tests were used to compare male and female test performance. For the total sample, no significant difference between males and females on Verbal, Performance and Full Scale IQ were found. On the factor indices, females scored marginally higher than males on Processing Speed at a level which was approaching significance (p = 0.105), but no significant differences were found. On subtest performance, females significantly outperformed males on Digit Symbol (p = 0.020). Differences which were approaching significance were found on Information (p = 0.133) in favour of males, and on Matrix Reasoning (p = 0.092) in favour of females. For subgroups of the total sample, the most significant differences in test performance were found for the African First Language private/"Model C" school cohort in favour of females. Thus the overriding implication that emerged from this research was that on this relatively highly educated sample, no significant gender differences in cognitive ability were apparent.
- Full Text:
- Date Issued: 2000
- Authors: Muirhead, Joanne
- Date: 2000
- Subjects: Wechsler Adult Intelligence Scale , Sex differences (Psychology) , Intelligence tests -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3028 , http://hdl.handle.net/10962/d1002537 , Wechsler Adult Intelligence Scale , Sex differences (Psychology) , Intelligence tests -- South Africa
- Description: This study, which formed part of a larger research project, investigated the effect of gender on test performance on the Wechsler Adult Intelligence Scale - Third Edition (WAIS-III). The WAIS-III was administered to a sample of 68 participants in the Eastern Cape following the initiative of the Human Sciences Research Council to standardise the WAIS-III for a South African population. The participants, aged 19 to 30, were stratified according to language of origin (African or English First Language), educational attainment (matriculant or graduate), quality of education (Department of Education and Training or private/"Model C" school) and gender. Analyses of variance and two sample t tests were used to compare male and female test performance. For the total sample, no significant difference between males and females on Verbal, Performance and Full Scale IQ were found. On the factor indices, females scored marginally higher than males on Processing Speed at a level which was approaching significance (p = 0.105), but no significant differences were found. On subtest performance, females significantly outperformed males on Digit Symbol (p = 0.020). Differences which were approaching significance were found on Information (p = 0.133) in favour of males, and on Matrix Reasoning (p = 0.092) in favour of females. For subgroups of the total sample, the most significant differences in test performance were found for the African First Language private/"Model C" school cohort in favour of females. Thus the overriding implication that emerged from this research was that on this relatively highly educated sample, no significant gender differences in cognitive ability were apparent.
- Full Text:
- Date Issued: 2000
Queens, pseudoqueens and laying workers reproductive competition in the Cape Honeybee (Apis mellifera capensis Eschscholtz)
- Authors: Muerrle, Thomas Martin
- Date: 2008
- Subjects: Honeybee Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5750 , http://hdl.handle.net/10962/d1005437
- Description: In honeybees (Apis mellifera L.) the queen monopolises reproduction. However, especially after queen loss, workers can lay eggs, but are unable to mate. They produce haploid male offspring (drones) from unfertilised eggs via arrhenotokous parthenogenesis. In contrast, workers of the honeybee subspecies Apis mellifera capensis Eschscholtz typically produce diploid female offspring from unfertilised eggs thelytokously. After queen loss and without queen-derived brood A. m. capensis colonies can successfully requeen from worker-derived brood. This, however, is a relatively rare event in wild populations. Moreover, workerderived queens were described to be smaller, more worker-like and reproductively inferior. On the other hand, the fixation of the thelytokous trait relies mainly on sufficient numbers of viable drones produced by worker-derived queens. Small numbers of reproductively inferior worker-derived queens in A. m. capensis populations would be clearly counterintuitive. It is therefore necessary to quantify the significance of worker-dependant queen rearing pathways on the individual (queen) and on population level.Reproductive inferiority of worker-derived queens could not be confirmed on the individual (queen) level when comparing parameters indicating potential reproductive success of queen- and worker-derived queens. Queen- and worker-derived queens clearly showed a congruent range of reproductive performance. In queen rearing preference tests, increased acceptance of worker-derived female larvae was exactly counterbalanced by increased mortality, resulting in an equal number of eclosing virgin queens from an equal number of grafts in both test groups. Larval survival and successful eclosion is a prerequisite for a queen’s reproductive success. I found no difference in eclosion success for queen- and worker-derived virgin queens, indicating a similar potential for reproductive success in both queen types. Assessments of the developmental patterns of colonies headed by both queen and worker-derived queens in long-term experiments revealed no significant differences in reproductive success. Colonies headed by queen-derived queens and colonies headed by worker-derived queens could not be separated when comparing the different developmental pathways observed or from differences in worker-force. Reproductive dominance in A. m. capensis appeared tobe determined by a function of relative compositional and absolute quantitative pheromonal patterns, where individuals, which produce compositionally most queen-like blends in highest quantities, occupy top positions. Queen- and worker-derived virgin queens occupied intermediate positions between pseudoqueens and mated queens. However, no significant differences between the pheromonal status of queen- and worker-derived virgin queens were observed, suggesting a similar range of reproductive dominance for both queen types. In behavioural bioassays queen- and worker-derived virgin queens appeared to be similarly attractive to clustering workers and to drones in a drone congregation area, indicating no differences in potential reproductive success for queens from both origins for those parameters. The significant influence of the queen substance 9-ODA on attractiveness to workers and drones was confirmed. Rare requeening events from worker-derived female brood in queenless A.m. capensis do not satisfactorily explain the fixation of the thelytokous trait at a population level. I observed A. m. capensis worker ovipositing into empty artificial queen cell cups in queen-right colonies. The queen was confined behind a queen excluder grid in a separate compartment of the colony, to imitate reduced pheromonal flow, similar to swarming or superseding colonies. Eggs oviposited by workers in artificial queen cell cups were readily accepted for queen rearing and successful eclosion of viable virgin queens was observed. Consequently I suggested an alternative worker-dependant reproductive pathway in A. m. capensis, which was never described before: In swarming or superseding queenright colonies, laying workers may directly compete with the queen for reproductive success by ovipositing (instead of the queen) into natural queen cell cups. At a population level this reproductive tactic may result in large numbers of worker-derived queens of high reproductive quality in natural populations of A. m. capensis.
- Full Text:
- Date Issued: 2008
- Authors: Muerrle, Thomas Martin
- Date: 2008
- Subjects: Honeybee Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5750 , http://hdl.handle.net/10962/d1005437
- Description: In honeybees (Apis mellifera L.) the queen monopolises reproduction. However, especially after queen loss, workers can lay eggs, but are unable to mate. They produce haploid male offspring (drones) from unfertilised eggs via arrhenotokous parthenogenesis. In contrast, workers of the honeybee subspecies Apis mellifera capensis Eschscholtz typically produce diploid female offspring from unfertilised eggs thelytokously. After queen loss and without queen-derived brood A. m. capensis colonies can successfully requeen from worker-derived brood. This, however, is a relatively rare event in wild populations. Moreover, workerderived queens were described to be smaller, more worker-like and reproductively inferior. On the other hand, the fixation of the thelytokous trait relies mainly on sufficient numbers of viable drones produced by worker-derived queens. Small numbers of reproductively inferior worker-derived queens in A. m. capensis populations would be clearly counterintuitive. It is therefore necessary to quantify the significance of worker-dependant queen rearing pathways on the individual (queen) and on population level.Reproductive inferiority of worker-derived queens could not be confirmed on the individual (queen) level when comparing parameters indicating potential reproductive success of queen- and worker-derived queens. Queen- and worker-derived queens clearly showed a congruent range of reproductive performance. In queen rearing preference tests, increased acceptance of worker-derived female larvae was exactly counterbalanced by increased mortality, resulting in an equal number of eclosing virgin queens from an equal number of grafts in both test groups. Larval survival and successful eclosion is a prerequisite for a queen’s reproductive success. I found no difference in eclosion success for queen- and worker-derived virgin queens, indicating a similar potential for reproductive success in both queen types. Assessments of the developmental patterns of colonies headed by both queen and worker-derived queens in long-term experiments revealed no significant differences in reproductive success. Colonies headed by queen-derived queens and colonies headed by worker-derived queens could not be separated when comparing the different developmental pathways observed or from differences in worker-force. Reproductive dominance in A. m. capensis appeared tobe determined by a function of relative compositional and absolute quantitative pheromonal patterns, where individuals, which produce compositionally most queen-like blends in highest quantities, occupy top positions. Queen- and worker-derived virgin queens occupied intermediate positions between pseudoqueens and mated queens. However, no significant differences between the pheromonal status of queen- and worker-derived virgin queens were observed, suggesting a similar range of reproductive dominance for both queen types. In behavioural bioassays queen- and worker-derived virgin queens appeared to be similarly attractive to clustering workers and to drones in a drone congregation area, indicating no differences in potential reproductive success for queens from both origins for those parameters. The significant influence of the queen substance 9-ODA on attractiveness to workers and drones was confirmed. Rare requeening events from worker-derived female brood in queenless A.m. capensis do not satisfactorily explain the fixation of the thelytokous trait at a population level. I observed A. m. capensis worker ovipositing into empty artificial queen cell cups in queen-right colonies. The queen was confined behind a queen excluder grid in a separate compartment of the colony, to imitate reduced pheromonal flow, similar to swarming or superseding colonies. Eggs oviposited by workers in artificial queen cell cups were readily accepted for queen rearing and successful eclosion of viable virgin queens was observed. Consequently I suggested an alternative worker-dependant reproductive pathway in A. m. capensis, which was never described before: In swarming or superseding queenright colonies, laying workers may directly compete with the queen for reproductive success by ovipositing (instead of the queen) into natural queen cell cups. At a population level this reproductive tactic may result in large numbers of worker-derived queens of high reproductive quality in natural populations of A. m. capensis.
- Full Text:
- Date Issued: 2008
Geographical races of the honeybees (Apis Mellifera L.) of the Northern regions of Ethiopia
- Authors: Mohammed, Nuru Adgaba
- Date: 2003
- Subjects: Honeybee -- Ethiopia Honeybee -- Behavior -- Ethiopia Honeybee -- Ethiopia -- Morphology Honeybee -- Ecology -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5827 , http://hdl.handle.net/10962/d1007671
- Description: The ideal climatic conditions and diversity of floral resources allow Ethiopia to sustain millions of honeybee colonies. Beekeeping is widely practiced and plays a significant role in the livelihood of the farming community of the country. Despite this, information on the types of geographical races of honeybees, their behavioural characters and the related ecological factors are not established. In this work an attempt was made to characterise the honeybee populations of the northern parts of Ethiopia based on the analyses of morphological, behavioural and ecological characteristics. For morphological analysis, 155 honeybee colony samples from 31 localities were collected. 20 worker honeybees per colony sample totalled 3100 individual worker honeybees and thirteen morphological characters per bee, a total of 40 300 measurements were recorded following Ruttner's (1988) protocols. The behavioural characters such as reproductive swarming, migration, temperament and colony seasonal cycles were assessed based on survey work of a pre-structured questionnaire. Various univariate and multivariate statistical methods were employed to analyse the data. The principal components and step-wise linear discriminant analyses revealed the existence of four discrete morphoclusters or geographical races: A. m. jemenitica from eastern, northwestern and northern arid and semi-arid lowlands, A. m. scutellata from the western humid midlands, A. m. bandasii from sub-moist central highlands and A. m. monticola from the northern mountainous parts of the study areas. These different geographical races were found to be distinctively distributed in the different ecological parts of the study area. High intercolonial and intracolonial variances were observed in all localities, however particularly high values were obtained in areas of transitions between ecological zones indicating a region of gene flow or zones of hybridisation among the statistically defined populations. Such high variances were observed mostly in areas where A. m. jemenitica borders the other geographical races. Moreover. distinct behavioural variations were also noted among these geographical races. Generally. the highland and mountainous honeybees A. m. bandasii and A. m. monticola are relatively larger in body size. have less tendency to swarm. less inclination to migrate and are relatively gentle while the converse traits were noted for the lowlands and midlands honeybees A. m. jemenitica and A. m. scutellata. Both morphological and behavioural variations were highly correlated with environmental factors and the variations seem to be the result of long adaptation to the interrelated ecological factors in their respective areas. Variations in reproductive swarming periods were also noted among these honeybee populations as a result of variations in rainfall pattern. altitude and temperature in their respective ecological areas which are believed to alter the honeybee colonies' seasonal cycles and leads to partial temporal reproductive isolation among these different honeybee populations.
- Full Text:
- Date Issued: 2003
- Authors: Mohammed, Nuru Adgaba
- Date: 2003
- Subjects: Honeybee -- Ethiopia Honeybee -- Behavior -- Ethiopia Honeybee -- Ethiopia -- Morphology Honeybee -- Ecology -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5827 , http://hdl.handle.net/10962/d1007671
- Description: The ideal climatic conditions and diversity of floral resources allow Ethiopia to sustain millions of honeybee colonies. Beekeeping is widely practiced and plays a significant role in the livelihood of the farming community of the country. Despite this, information on the types of geographical races of honeybees, their behavioural characters and the related ecological factors are not established. In this work an attempt was made to characterise the honeybee populations of the northern parts of Ethiopia based on the analyses of morphological, behavioural and ecological characteristics. For morphological analysis, 155 honeybee colony samples from 31 localities were collected. 20 worker honeybees per colony sample totalled 3100 individual worker honeybees and thirteen morphological characters per bee, a total of 40 300 measurements were recorded following Ruttner's (1988) protocols. The behavioural characters such as reproductive swarming, migration, temperament and colony seasonal cycles were assessed based on survey work of a pre-structured questionnaire. Various univariate and multivariate statistical methods were employed to analyse the data. The principal components and step-wise linear discriminant analyses revealed the existence of four discrete morphoclusters or geographical races: A. m. jemenitica from eastern, northwestern and northern arid and semi-arid lowlands, A. m. scutellata from the western humid midlands, A. m. bandasii from sub-moist central highlands and A. m. monticola from the northern mountainous parts of the study areas. These different geographical races were found to be distinctively distributed in the different ecological parts of the study area. High intercolonial and intracolonial variances were observed in all localities, however particularly high values were obtained in areas of transitions between ecological zones indicating a region of gene flow or zones of hybridisation among the statistically defined populations. Such high variances were observed mostly in areas where A. m. jemenitica borders the other geographical races. Moreover. distinct behavioural variations were also noted among these geographical races. Generally. the highland and mountainous honeybees A. m. bandasii and A. m. monticola are relatively larger in body size. have less tendency to swarm. less inclination to migrate and are relatively gentle while the converse traits were noted for the lowlands and midlands honeybees A. m. jemenitica and A. m. scutellata. Both morphological and behavioural variations were highly correlated with environmental factors and the variations seem to be the result of long adaptation to the interrelated ecological factors in their respective areas. Variations in reproductive swarming periods were also noted among these honeybee populations as a result of variations in rainfall pattern. altitude and temperature in their respective ecological areas which are believed to alter the honeybee colonies' seasonal cycles and leads to partial temporal reproductive isolation among these different honeybee populations.
- Full Text:
- Date Issued: 2003
Price discovery, price behaviour, and efficiency of selected grain commodities traded on the agricultural products division of the JSE securities exchange
- Authors: Viljoen, Christo
- Date: 2004
- Subjects: Johannesburg Stock Exchange Stock exchanges -- South Africa International economic relations Primary commodities -- South Africa Grain trade -- South Africa Financial futures -- South Africa Price regulation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:952 , http://hdl.handle.net/10962/d1002686
- Description: Agricultural commodity derivatives were first introduced in South Africa in 1996 after the deregulation of the former marketing system. In the context of its proposed functions, namely price discovery and risk management, the question arose as to whether the futures market developed over time to performed its role efficiently. According to the Efficient Markets Hypothesis (EMH) an efficient market is one that accurately incorporates all information available at any point in time. The purpose of the research was to address the issue of price discovery efficiency, firstly, focusing on the weak-form methodology. Secondly, considering the behaviour of futures prices over time, the study addressed the concern of anomalies in daily returns – phenomena contradictory to the EMH by implication. Thirdly, as a means of defining the sources of inefficiency, the role of scheduled public information and its impact on futures prices was examined. Therefore, the primary objective of the research was to investigate and identify the main components of agricultural futures market inefficiency within the unique price formation structure of South African grain markets. The assessment of this problem is important in terms of evaluating the growth and development of the futures market for different grain commodities to date. The Exchange needs to review rules and regulations on a frequent basis in order to ensure proper functioning at all times especially in the case of a relatively new and fast growing market. The study contributed to the knowledge of understanding the price adjustment process and its implications for market efficiency in the context of the three grain markets considered. The weak-form efficiency was tested using a co-integration based model. Analysing daily spot and futures prices of white maize, yellow maize, and wheat, results indicated that all three markets were efficient and unbiased. Non-parametric tests revealed the significant presence of day-of-the-week and turn-of-the-month effects in the futures returns of the three commodities. Further non-parametric analyses suggested a high degree of uncertainty in futures returns around scheduled agricultural and macroeconomic information release dates also contributing significantly to the identified anomalies. It was concluded that (1) the markets’ ability to anticipate the contents of future information to be released, (2) the current skewed size distribution of broking members, (3) the significant role of the R/$ exchange rate in the price formation process of South African grains and, therefore, (4) the relationship to and influence of the broader economy enhanced the return effects (anomalies) creating opportunity for profitable arbitrage. This conclusion was mainly attributed to South Africa’s status as a price-taker in the world grain complex as well as the relatively short existence of the local agricultural futures markets.
- Full Text:
- Date Issued: 2004
- Authors: Viljoen, Christo
- Date: 2004
- Subjects: Johannesburg Stock Exchange Stock exchanges -- South Africa International economic relations Primary commodities -- South Africa Grain trade -- South Africa Financial futures -- South Africa Price regulation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:952 , http://hdl.handle.net/10962/d1002686
- Description: Agricultural commodity derivatives were first introduced in South Africa in 1996 after the deregulation of the former marketing system. In the context of its proposed functions, namely price discovery and risk management, the question arose as to whether the futures market developed over time to performed its role efficiently. According to the Efficient Markets Hypothesis (EMH) an efficient market is one that accurately incorporates all information available at any point in time. The purpose of the research was to address the issue of price discovery efficiency, firstly, focusing on the weak-form methodology. Secondly, considering the behaviour of futures prices over time, the study addressed the concern of anomalies in daily returns – phenomena contradictory to the EMH by implication. Thirdly, as a means of defining the sources of inefficiency, the role of scheduled public information and its impact on futures prices was examined. Therefore, the primary objective of the research was to investigate and identify the main components of agricultural futures market inefficiency within the unique price formation structure of South African grain markets. The assessment of this problem is important in terms of evaluating the growth and development of the futures market for different grain commodities to date. The Exchange needs to review rules and regulations on a frequent basis in order to ensure proper functioning at all times especially in the case of a relatively new and fast growing market. The study contributed to the knowledge of understanding the price adjustment process and its implications for market efficiency in the context of the three grain markets considered. The weak-form efficiency was tested using a co-integration based model. Analysing daily spot and futures prices of white maize, yellow maize, and wheat, results indicated that all three markets were efficient and unbiased. Non-parametric tests revealed the significant presence of day-of-the-week and turn-of-the-month effects in the futures returns of the three commodities. Further non-parametric analyses suggested a high degree of uncertainty in futures returns around scheduled agricultural and macroeconomic information release dates also contributing significantly to the identified anomalies. It was concluded that (1) the markets’ ability to anticipate the contents of future information to be released, (2) the current skewed size distribution of broking members, (3) the significant role of the R/$ exchange rate in the price formation process of South African grains and, therefore, (4) the relationship to and influence of the broader economy enhanced the return effects (anomalies) creating opportunity for profitable arbitrage. This conclusion was mainly attributed to South Africa’s status as a price-taker in the world grain complex as well as the relatively short existence of the local agricultural futures markets.
- Full Text:
- Date Issued: 2004
Operationally defining sexual orientation : towards the development of a fundamental measure of adolescent sexual responsiveness variations
- Authors: Heath, Lance Julian
- Date: 2005
- Subjects: Sexual orientation Homosexuality Psychometrics Teenagers--Sexual behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1681 , http://hdl.handle.net/10962/d1003564
- Description: Much published work has pointed to the need for the development of a sound operational definition of sexual orientation in order to enable the research in this area to progress. To contribute to this process the current research set out to develop two measures of sexual orientation and examine their psychometric properties. In order to develop relevant tools historical, conceptual and operational definitions of sexual orientation were critically examined and standard questionnaire development techniques applied. The first scale consisted of 32 items and was administered to a total of 835 adolescents, comprising three sub-groups (189 Grade 11 Scholars, 547 First Year and 99 Third Year Psychology Students). A Cronbach alpha coefficient of 0.85 was calculated indicating that this instrument had very good internal consistency reliability. Similar factors emerged in each of the sample sub-groups when factor analyses were performed suggesting that this instrument has good external and construct validities. These factors each had respectable Cronbach alpha coefficients indicating their own internal consistency. The four factors which consistently emerged were Same Sex Responsiveness, Opposite Sex Responsiveness, Previous Month’s Same Sex Responsiveness and Previous Month’s Opposite Sex Responsiveness. The second scale consisted of 16 items and was administered to 646 adolescents, comprising the latter two sub-groups referred to above. A Cronbach alpha coefficient of 0.82 was calculated indicating that this instrument also had very good internal consistency reliability. Once again similar factors with generally good internal consistency emerged in factor analysis suggesting that this too was a valid instrument. The factors that emerged from the second scale were Same Sex Responsiveness, Unattractive Opposite Sex Responsiveness, Attractive Opposite Sex Responsiveness and Attraction. Future developments, adjustments and applications of the instruments as well as implications for the arena of sexual orientation research are discussed. In the light of the dearth of information with regard to the sexual orientations of South African adolescents the current study also briefly explored and presented the sample’s responses in terms of the dimensions of each questionnaire as well as how each emerging factor related to the demographics (education level, gender, sexual orientation self-label and age) of the sample.
- Full Text:
- Date Issued: 2005
- Authors: Heath, Lance Julian
- Date: 2005
- Subjects: Sexual orientation Homosexuality Psychometrics Teenagers--Sexual behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1681 , http://hdl.handle.net/10962/d1003564
- Description: Much published work has pointed to the need for the development of a sound operational definition of sexual orientation in order to enable the research in this area to progress. To contribute to this process the current research set out to develop two measures of sexual orientation and examine their psychometric properties. In order to develop relevant tools historical, conceptual and operational definitions of sexual orientation were critically examined and standard questionnaire development techniques applied. The first scale consisted of 32 items and was administered to a total of 835 adolescents, comprising three sub-groups (189 Grade 11 Scholars, 547 First Year and 99 Third Year Psychology Students). A Cronbach alpha coefficient of 0.85 was calculated indicating that this instrument had very good internal consistency reliability. Similar factors emerged in each of the sample sub-groups when factor analyses were performed suggesting that this instrument has good external and construct validities. These factors each had respectable Cronbach alpha coefficients indicating their own internal consistency. The four factors which consistently emerged were Same Sex Responsiveness, Opposite Sex Responsiveness, Previous Month’s Same Sex Responsiveness and Previous Month’s Opposite Sex Responsiveness. The second scale consisted of 16 items and was administered to 646 adolescents, comprising the latter two sub-groups referred to above. A Cronbach alpha coefficient of 0.82 was calculated indicating that this instrument also had very good internal consistency reliability. Once again similar factors with generally good internal consistency emerged in factor analysis suggesting that this too was a valid instrument. The factors that emerged from the second scale were Same Sex Responsiveness, Unattractive Opposite Sex Responsiveness, Attractive Opposite Sex Responsiveness and Attraction. Future developments, adjustments and applications of the instruments as well as implications for the arena of sexual orientation research are discussed. In the light of the dearth of information with regard to the sexual orientations of South African adolescents the current study also briefly explored and presented the sample’s responses in terms of the dimensions of each questionnaire as well as how each emerging factor related to the demographics (education level, gender, sexual orientation self-label and age) of the sample.
- Full Text:
- Date Issued: 2005
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