An investigation into XSets of primitive behaviours for emergent behaviour in stigmergic and message passing antlike agents
- Authors: Chibaya, Colin
- Date: 2014
- Subjects: Ants -- Behavior -- Computer programs , Insects -- Behavior -- Computer programs , Ant communities -- Behavior , Insect societies
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4698 , http://hdl.handle.net/10962/d1012965
- Description: Ants are fascinating creatures - not so much because they are intelligent on their own, but because as a group they display compelling emergent behaviour (the extent to which one observes features in a swarm which cannot be traced back to the actions of swarm members). What does each swarm member do which allows deliberate engineering of emergent behaviour? We investigate the development of a language for programming swarms of ant agents towards desired emergent behaviour. Five aspects of stigmergic (pheromone sensitive computational devices in which a non-symbolic form of communication that is indirectly mediated via the environment arises) and message passing ant agents (computational devices which rely on implicit communication spaces in which direction vectors are shared one-on-one) are studied. First, we investigate the primitive behaviours which characterize ant agents' discrete actions at individual levels. Ten such primitive behaviours are identified as candidate building blocks of the ant agent language sought. We then study mechanisms in which primitive behaviours are put together into XSets (collection of primitive behaviours, parameter values, and meta information which spells out how and when primitive behaviours are used). Various permutations of XSets are possible which define the search space for best performer XSets for particular tasks. Genetic programming principles are proposed as a search strategy for best performer XSets that would allow particular emergent behaviour to occur. XSets in the search space are evolved over various genetic generations and tested for abilities to allow path finding (as proof of concept). XSets are ranked according to the indices of merit (fitness measures which indicate how well XSets allow particular emergent behaviour to occur) they achieve. Best performer XSets for the path finding task are identifed and reported. We validate the results yield when best performer XSets are used with regard to normality, correlation, similarities in variation, and similarities between mean performances over time. Commonly, the simulation results yield pass most statistical tests. The last aspect we study is the application of best performer XSets to different problem tasks. Five experiments are administered in this regard. The first experiment assesses XSets' abilities to allow multiple targets location (ant agents' abilities to locate continuous regions of targets), and found out that best performer XSets are problem independent. However both categories of XSets are sensitive to changes in agent density. We test the influences of individual primitive behaviours and the effects of the sequences of primitive behaviours to the indices of merit of XSets and found out that most primitive behaviours are indispensable, especially when specific sequences are prescribed. The effects of pheromone dissipation to the indices of merit of stigmergic XSets are also scrutinized. Precisely, dissipation is not causal. Rather, it enhances convergence. Overall, this work successfully identify the discrete primitive behaviours of stigmergic and message passing ant-like devices. It successfully put these primitive behaviours together into XSets which characterize a language for programming ant-like devices towards desired emergent behaviour. This XSets approach is a new ant language representation with which a wider domain of emergent tasks can be resolved.
- Full Text:
- Date Issued: 2014
- Authors: Chibaya, Colin
- Date: 2014
- Subjects: Ants -- Behavior -- Computer programs , Insects -- Behavior -- Computer programs , Ant communities -- Behavior , Insect societies
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4698 , http://hdl.handle.net/10962/d1012965
- Description: Ants are fascinating creatures - not so much because they are intelligent on their own, but because as a group they display compelling emergent behaviour (the extent to which one observes features in a swarm which cannot be traced back to the actions of swarm members). What does each swarm member do which allows deliberate engineering of emergent behaviour? We investigate the development of a language for programming swarms of ant agents towards desired emergent behaviour. Five aspects of stigmergic (pheromone sensitive computational devices in which a non-symbolic form of communication that is indirectly mediated via the environment arises) and message passing ant agents (computational devices which rely on implicit communication spaces in which direction vectors are shared one-on-one) are studied. First, we investigate the primitive behaviours which characterize ant agents' discrete actions at individual levels. Ten such primitive behaviours are identified as candidate building blocks of the ant agent language sought. We then study mechanisms in which primitive behaviours are put together into XSets (collection of primitive behaviours, parameter values, and meta information which spells out how and when primitive behaviours are used). Various permutations of XSets are possible which define the search space for best performer XSets for particular tasks. Genetic programming principles are proposed as a search strategy for best performer XSets that would allow particular emergent behaviour to occur. XSets in the search space are evolved over various genetic generations and tested for abilities to allow path finding (as proof of concept). XSets are ranked according to the indices of merit (fitness measures which indicate how well XSets allow particular emergent behaviour to occur) they achieve. Best performer XSets for the path finding task are identifed and reported. We validate the results yield when best performer XSets are used with regard to normality, correlation, similarities in variation, and similarities between mean performances over time. Commonly, the simulation results yield pass most statistical tests. The last aspect we study is the application of best performer XSets to different problem tasks. Five experiments are administered in this regard. The first experiment assesses XSets' abilities to allow multiple targets location (ant agents' abilities to locate continuous regions of targets), and found out that best performer XSets are problem independent. However both categories of XSets are sensitive to changes in agent density. We test the influences of individual primitive behaviours and the effects of the sequences of primitive behaviours to the indices of merit of XSets and found out that most primitive behaviours are indispensable, especially when specific sequences are prescribed. The effects of pheromone dissipation to the indices of merit of stigmergic XSets are also scrutinized. Precisely, dissipation is not causal. Rather, it enhances convergence. Overall, this work successfully identify the discrete primitive behaviours of stigmergic and message passing ant-like devices. It successfully put these primitive behaviours together into XSets which characterize a language for programming ant-like devices towards desired emergent behaviour. This XSets approach is a new ant language representation with which a wider domain of emergent tasks can be resolved.
- Full Text:
- Date Issued: 2014
Peer group supervision as an adjunct to individual supervision: an investigation of models of learning
- Akhurst, Jacqueline Elizabeth
- Authors: Akhurst, Jacqueline Elizabeth
- Date: 2000
- Subjects: Peer-group tutoring of students Psychotherapy -- Study and teaching -- Supervision Psychology -- Supervision of
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2922 , http://hdl.handle.net/10962/d1002431
- Description: Supervision of practice makes an important contribution to the development of psychotherapeutic skills in the training of psychologists (Bernard and Goodyear, 1998). Much research has, until recently, focussed on dyadic, hierarchical models of supervision, even though other forms of supervision have been developed. Peer group supervision has had little attention in the literature, although it is a common form of supervision utilised by psychologists in practice (Lewis, Greenburg and Hatch, 1988). A review of the literature considers the purposes of supervision; elements of dyadic supervision; various forms of group, peer and peer group supervision; and the leaming process in supervision. The development and implementation of a peer supervision group (pSG) of intern psychologists within the training setting of a University is described in this study. The PSG model was developed from the model proposed by Wilbur, Roberts-Wilbur, Morris, Betz and Hart (1991). Transcripts from nine audio-taped PSG sessions were analysed, and a comparison with four audio-taped dyadic supervision sessions was then undertaken. Grounded Theory methodology was employed in the design of the study and analysis of the data. The form and content of the two models of supervision were examined, with particular attention to the perspective of the trainees' learning experiences. The relative merits of both forms of supervision were assessed, and this analysis clearly demonstrates that peer group supervision has the potential to complement dyadic supervision by contributing differing learning experiences. A model of key influences upon, and effects of, participation in the two forms of supervision has been developed. Suggestions are made of ways in which dyadic supervision may be optimised, and recommendations for further development of the PSG emerge. The results were then considered from a neo-Vygotskian perspective. This enabled the findings to be linked to a comprehensive theory of learning, pointing to the key role of speech in thinking, and the contributions of the various forms of dialogue to deepened understandings. The discussion includes: consideration of techniques which enable trainees to obtain assistance from both more experienced practitioners as well as from their peers; an exploration of aspects of subjectivity and intersubjectivity; and contextual influences which have bearing on the study. This study identifies the need for further consideration of the supervision process in South Africa, and makes recommendations for the training of supervisors. The neo-Vygotskian model offers great promise both as a framework for understanding the leaming process in. supervision, and for developing guidelines for enhancing supervisory practice.
- Full Text:
- Date Issued: 2000
- Authors: Akhurst, Jacqueline Elizabeth
- Date: 2000
- Subjects: Peer-group tutoring of students Psychotherapy -- Study and teaching -- Supervision Psychology -- Supervision of
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2922 , http://hdl.handle.net/10962/d1002431
- Description: Supervision of practice makes an important contribution to the development of psychotherapeutic skills in the training of psychologists (Bernard and Goodyear, 1998). Much research has, until recently, focussed on dyadic, hierarchical models of supervision, even though other forms of supervision have been developed. Peer group supervision has had little attention in the literature, although it is a common form of supervision utilised by psychologists in practice (Lewis, Greenburg and Hatch, 1988). A review of the literature considers the purposes of supervision; elements of dyadic supervision; various forms of group, peer and peer group supervision; and the leaming process in supervision. The development and implementation of a peer supervision group (pSG) of intern psychologists within the training setting of a University is described in this study. The PSG model was developed from the model proposed by Wilbur, Roberts-Wilbur, Morris, Betz and Hart (1991). Transcripts from nine audio-taped PSG sessions were analysed, and a comparison with four audio-taped dyadic supervision sessions was then undertaken. Grounded Theory methodology was employed in the design of the study and analysis of the data. The form and content of the two models of supervision were examined, with particular attention to the perspective of the trainees' learning experiences. The relative merits of both forms of supervision were assessed, and this analysis clearly demonstrates that peer group supervision has the potential to complement dyadic supervision by contributing differing learning experiences. A model of key influences upon, and effects of, participation in the two forms of supervision has been developed. Suggestions are made of ways in which dyadic supervision may be optimised, and recommendations for further development of the PSG emerge. The results were then considered from a neo-Vygotskian perspective. This enabled the findings to be linked to a comprehensive theory of learning, pointing to the key role of speech in thinking, and the contributions of the various forms of dialogue to deepened understandings. The discussion includes: consideration of techniques which enable trainees to obtain assistance from both more experienced practitioners as well as from their peers; an exploration of aspects of subjectivity and intersubjectivity; and contextual influences which have bearing on the study. This study identifies the need for further consideration of the supervision process in South Africa, and makes recommendations for the training of supervisors. The neo-Vygotskian model offers great promise both as a framework for understanding the leaming process in. supervision, and for developing guidelines for enhancing supervisory practice.
- Full Text:
- Date Issued: 2000
The evaluation of melatonin as a possible antidepressive
- Authors: Skene, Debra Jean
- Date: 1980
- Subjects: Melatonin , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3728 , http://hdl.handle.net/10962/d1001465
- Description: Melatonin, a hormone of the pineal gland, was evaluated in a variety of animal models of depression. Measurements of the frog righting reflex and rat locomotor activity showed that low doses of melatonin have a serotonin-like potentiating effect following monoamine oxidase inhibition. High doses of melatonin caused a reduction in the duration of rat immobility in the Porsolt model of depression and exerted a chlorpromazine-like effect on conditioned avoidance behaviour. In view of the indoleamine hypothesis of depressive disorders, the possibility of melatonin being a potential antidepressive is discussed and it is concluded that melatonin might be useful in the treatment of "agitated" depressions
- Full Text:
- Date Issued: 1980
- Authors: Skene, Debra Jean
- Date: 1980
- Subjects: Melatonin , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3728 , http://hdl.handle.net/10962/d1001465
- Description: Melatonin, a hormone of the pineal gland, was evaluated in a variety of animal models of depression. Measurements of the frog righting reflex and rat locomotor activity showed that low doses of melatonin have a serotonin-like potentiating effect following monoamine oxidase inhibition. High doses of melatonin caused a reduction in the duration of rat immobility in the Porsolt model of depression and exerted a chlorpromazine-like effect on conditioned avoidance behaviour. In view of the indoleamine hypothesis of depressive disorders, the possibility of melatonin being a potential antidepressive is discussed and it is concluded that melatonin might be useful in the treatment of "agitated" depressions
- Full Text:
- Date Issued: 1980
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