Cognitive flexibility can be described as adaptive ability to change one's behavior in response to the environment. Psychological tests measure cognitive flexibility mainly as an ability to switch between different cues, tasks or objects. This thesis is focused on cognitive flexibility in patients with obsessive compulsive disorder (OCD). To assess it, participants were tested in two different virtual tests of cognitive flexibility in spatial navigation task: Active allothetic place preference and Active allothetic place avoidance. In one of the tests participants have to navigate in rotating arena towads invisble goal (AAPP). In the other one they have to avoid invisible sector where time is counted upon entering (AAPA). As the sector and goal are visually imperceptible, participants have to use only cues inside and outside the arena and are also informed about entering the sector by sound signal. The sector changes its position from stable position in room frame to stable position in arena frame between conditions. Therefore, participants have to learn to switch between room and arena frame to sucessfully solve the task. Results of this study suggest that OCD patients are significantly worse in estimating position of the goal in AAPP, especially after change of condition. Further comparsion of...

Die vorliegende Studienarbeit beschäftigt sich mit der Fragestellung, inwiefern sich Revealed-Preference-Daten aus der deutschen Mobilitätsbefragung "Mobilität in Städten" SrV 2008 dazu eignen, um basierend auf denen im Datensatz enthaltenen Wegen Verkehrsmittelwahlmodelle zu schätzen. Dazu wurden Wegedaten aus der Befragung verwendet, und die Wahlalternativen mit Hilfe der Google Directions API rekonstruiert. Mit den rekonstruierten Variablen Reisezeit und Reisekosten sowie verschiedenen sozioökonomischen und externen Variablen aus SrV 2008 wurden verschiedene Wahlmodelle geschätzt. Durch schrittweises Hinzufügen der Variablen konnte das Modell immer weiter verbessert werden. Wie zu erwarten, erwiesen sich dabei die Reisezeit und die Reisekosten als hoch signifikant. Von den restlichen Variablen waren jedoch lediglich das Geschlecht der befragten Person sowie die Wettersituation zum Zeitpunkt der Wahlentscheidung signifikant. Für das finale Modell wurden Zeitkostensätze errechnet und mit verschiedenen europäischen Studien verglichen. Die errechneten Zeitkostensätze erwiesen sich dabei als plausibel. Die SrV-Daten eignen sich also für die Schätzung von Wahlmodellen.:1 Einleitung 1 1.1 Vorstellung des Themas 1 1.2 Ziel dieser Arbeit 1 1.3 Gliederung dieser Arbeit 2 1.4 Wesentliche Ergebnisse 2 2 Theoretischer Hintergrund 3 2.1 Diskrete Wahltheorie 3 2.1.1 Deterministischer Nutzen 4 2.1.2 Stochastischer Störterm 5 2.1.3 Logit-Modell 6 2.2 Parameterschätzung 8 2.2.1 t-Test 9 2.2.2 Likelihood-Ratio Test 9 2.2.3 Likelihood-Ratio-Index 10 2.3 Datenquellen 10 3 Generierung eines RP-Datensatzes aus SrV-Daten 13 3.1 SrV 2008 13 3.2 Auswahl an Variablen und Datensätzen 13 3.3 Rekonstruktion der generischen Variablen 15 3.3.1 Google Directions API 15 3.3.2 Automatisierte API-Abfrage 16 3.3.3 Reisekosten 17 3.4 Erzeugter Datensatz 18 4 Modellentwicklung und Parameterschätzung 21 4.1 Entwicklung des Wahlmodells 21 4.2 Parameterschätzung mit Biogeme 24 4.3 Anwendung der Parameterschätzung auf die SrV-Daten 28 5 Diskussion der Modellergebnisse 33 5.1 Darstellung der Nutzeneinflüsse 33 5.2 Zeitkostensätze 35 5.3 Fehlerquellen 37 5.4 Fazit 38 Literaturverzeichnis 41 Datenquellen 45 Anhang 49 / The following thesis analyzes, if revealed preference data from the German mobility survey "Mobilität in Städten" SrV 2008 is suited to estimate mode choice models. For that purpose, trip data from the survey was used and the different choice alternatives were reconstructed with the Google Directions API. Several mode choice models were estimated with the help of the reconstructed variables travel time and travel costs plus several socioeconomic and external variables from SrV 2008. The variables were added to the model step by step, thereby the quality of the model improved. As expected, travel time and travel costs were highly significant. However from the remaining variables only the gender of the person and the weather at the time of the trip were significant. For the final model, values of time were calculated and these were compared with values from different European studies. The calculated values of time proved to be feasible. Therefore, SrV data is suited to be used for mode choice models.:1 Einleitung 1 1.1 Vorstellung des Themas 1 1.2 Ziel dieser Arbeit 1 1.3 Gliederung dieser Arbeit 2 1.4 Wesentliche Ergebnisse 2 2 Theoretischer Hintergrund 3 2.1 Diskrete Wahltheorie 3 2.1.1 Deterministischer Nutzen 4 2.1.2 Stochastischer Störterm 5 2.1.3 Logit-Modell 6 2.2 Parameterschätzung 8 2.2.1 t-Test 9 2.2.2 Likelihood-Ratio Test 9 2.2.3 Likelihood-Ratio-Index 10 2.3 Datenquellen 10 3 Generierung eines RP-Datensatzes aus SrV-Daten 13 3.1 SrV 2008 13 3.2 Auswahl an Variablen und Datensätzen 13 3.3 Rekonstruktion der generischen Variablen 15 3.3.1 Google Directions API 15 3.3.2 Automatisierte API-Abfrage 16 3.3.3 Reisekosten 17 3.4 Erzeugter Datensatz 18 4 Modellentwicklung und Parameterschätzung 21 4.1 Entwicklung des Wahlmodells 21 4.2 Parameterschätzung mit Biogeme 24 4.3 Anwendung der Parameterschätzung auf die SrV-Daten 28 5 Diskussion der Modellergebnisse 33 5.1 Darstellung der Nutzeneinflüsse 33 5.2 Zeitkostensätze 35 5.3 Fehlerquellen 37 5.4 Fazit 38 Literaturverzeichnis 41 Datenquellen 45 Anhang 49

Die vorliegende Dissertation setzt sich damit auseinander, wie das Zusammenspiel von essensbezogener Umwelt und Kognition Ernährungsentscheidungen beeinflusst. Im ersten Manuskript, “When Diets Last: Lower Cognitive Complexity Increases Diet Adherence” wird die Bedeutung der kognitiven Komplexität von Ernährungsregeln für das Einhalten einer Diät untersucht. Können Diäten scheitern, weil sie aus kognitiver Perspektive zu komplex sind, z.B. weil sich Diäthaltende nicht alle wichtigen Informationen merken oder verarbeiten können? 1136 Diäthaltende nahmen an einer längsschnittlichen Onlinestudie teil. Vorangegangenes Diätverhalten, Selbstwirksamkeit, Planung und wahrgenommene Regelschwierigkeit erhöhten das Risiko, die Diät vorzeitig aufzugeben, wobei Selbstwirksamkeit und wahrgenommene Regelschwierigkeit die einflussreichsten Faktoren waren. Im zweiten Manuskript „Meat Label Design: Effects on Stage Progression, Risk Perception, and Product Evaluation” wird der Einfluss gesundheitsrelevanter Information auf Labeln für Produktbewertung und Intention, Tierhaltung und Inhaltsstoffe von Lebensmitteln in die Kaufentscheidung einzubeziehen, untersucht. Es wurde betrachtet, wie Inhalt und Kontext (separate versus conjoint Darbietung) der Labelinformation die Bewertung von Fleischprodukten beeinflusst. Die Ergebnisse zeigen, dass sich bei einer conjoint im Gegensatz zur separaten Darbietung die Bewertung der Produkte umkehrt. Darüber hinaus hatten Personen, die zuvor nicht motiviert waren gesundheitsrelevante Aspekte in ihr Einkaufsverhalten einzubeziehen, nach Betrachten der Label eine höhere Intention diese zu berücksichtigen. Im dritten Manuskript, „Predicting Children’s Meal Preferences: How Much Do Parents Know?“, wurden Präferenzvorhersagen bezüglich der Essensentscheidungen Anderer erforscht. Es wurde untersucht, wie gut und mit Hilfe welcher Information Eltern die Mittagessenpräferenzen ihrer Kinder vorhersagen. Die Vorhersagegenauigkeit der Eltern entsprach der Stabilität der Essenspräferenzen ihrer Kinder, d.h. dass die Eltern so genau waren, wie möglich. Die Ergebnisse suggerieren, dass Eltern vor allem spezifisches Wissen über die Präferenzen ihrer Kinder und Projektion ihrer eigenen Vorlieben für die Vorhersagen nutzten. / This dissertation focuses on food-related decision making, in particular, how food related environments and cognition interact to determine people’s food choices. The first manuscript, “When Diets Last: Lower Cognitive Complexity Increases Diet Adherence,” investigates the role of the cognitive complexity in diet adherence. Can weight loss diets fail because they are too complicated from a cognitive point of view, meaning that dieters are not able to recall or process the diet rules? The impact of excessive cognitive demands on diet adherence were investigated with 1,136 dieters in a longitudinal online-questionnaire. We measured perceived rule complexity controlling for other factors known to influence adherence. Previous diet behavior, self-efficacy, planning and perceived rule complexity predicted an increased risk to quit the diet prematurely, with self-efficacy and diet complexity being the strongest factors. The second manuscript, “Meat Label Design: Effects on Stage Progression, Risk Perception, and Product Evaluation,” presents two studies which tested the impact of health-related meat labels on product evaluation and intention. Specifically, the studies examined how informational content and the context (separate vs. conjoint evaluation) in which labels are assessed influence the evaluation of meat products. The results showed that conjoint assessment of labels can lead to contrary product rankings compared to separate evaluations. Moreover, the results suggest that being exposed to food labels containing specific health-relevant information can increase motivation to consider health aspects in those consumers without previous intention to do so. The third manuscript, “Predicting Children’s Meal Preferences: How Much Do Parents Know?” investigated prediction behavior concerning other people’s food choices. In particular, it asked how accurately and what cues parents use to predict their children’s meal choices. Overall, parents’ prediction accuracy matched the stability of children’s meal choices, implying that accuracy was as high as can be expected. The results suggest parents were able to obtain high predictive accuracy by using specific knowledge about their child’s likes and projecting their own preferences.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Richard H. Mattson / Subjects of this research were 64 adolescents receiving treatment at two behavioral health service institutions located in an urban mid-western city. Both institutions provided horticultural therapy and non-horticultural therapy programs. Research subjects were adolescents with diverse treatment needs and their responses on research questions were inconsistent compared to other related studies with general population. Current research assessed the adolescents with horticultural therapy treatment and without horticultural therapy treatment in three aspects. First, the levels of psychological aspects of adolescents were assessed with the Rosenberg Self-Esteem Scale and Nowicki-Strickland Locus of Control Scale for Children. The levels of self-esteem and locus of control of adolescents with horticultural therapy treatment were not significantly different from those of adolescents without horticultural therapy treatment at both institutions. Based on the different level of worthiness and competence factors, it is recommended to design horticultural therapy programs focused on improving the worthiness factor of self-esteem. Second, the pastoralism disposition of the Children's Environmental Response Inventory was used to assess the level of environmental attitude of the adolescents with and without horticultural therapy treatment. Horticultural experience and environmental attitude had a positive relationship with most subjects. At one institution, the level of environmental attitude of the adolescents with horticultural therapy treatment was significantly higher than the adolescents without horticultural therapy treatment. The adolescents at the horticultural therapy program which was scheduled more frequently showed higher environmental attitude scores. To improve environmental attitude of adolescents, horticultural therapy program should provide diversity and abundant opportunities of horticultural experiences. Third, basic horticultural knowledge was tested with the Basic Horticultural Knowledge Questionnaire. Vegetable/fruit consumption and preference were described with the Vegetable and Fruit Preference and Consumption Survey. Basic horticultural knowledge scores of the horticultural therapy group were significantly higher than that of the non-horticultural therapy group at one institution, but the scores were similar between the two groups at the other institution. Basic horticultural knowledge of subjects was significantly correlated to their vegetable and fruit consumption. To increase vegetable/fruit consumption, horticultural therapy programs should set goals to incorporate nutrition education.

Doctor of Philosophy / Department of Psychological Sciences / Jerome Frieman / Spotted hyenas (Crocuta crocuta) live in highly-complex, female-dominated groups called “clans.” Due to their social arrangement, spotted hyenas were a logical species on which to test the social complexity hypothesis. In the present study, they were presented with a series of puzzle boxes designed to test problem-solving behavior. The five puzzles varied in difficulty. All spotted hyenas solved the puzzle with the lowest difficulty level, five out of six solved the medium puzzles at least once, and one out of six solved the high difficulty puzzle. Some decreases in behavior diversity and time working on the puzzles were observed over successful trials; however, the decreases were only significant for successful trials of one medium-level puzzle. Decreases in work time were observed for some unsuccessful trials and the decrease was statistically significant for the highest difficulty puzzle. Overall, spotted hyenas were proficient at problem solving in the present study. Social learning is an important component of a lengthy juvenile period for spotted hyenas, and they have also been shown to influence one another’s feeding behavior. Furthermore, spotted hyenas participate in scramble competition when feeding and forage for and hoard food. In light of these behaviors, social learning was examined using the social transmission of a flavor preference (STFP) procedure. STFP was not observed overall. The sex of the subjects did not significantly influence the results; however, subjects that interacted with each other longer were significantly more likely to show STFP. The STFP procedure may not be sensitive enough to detect social learning in spotted hyenas. Perhaps spotted hyenas have no need to learn STFP due to their digestive and/or immune systems. The results of the current experiments make important contributions to existing knowledge. Data from other species like spotted hyenas are vital for evaluating the generality of the social complexity hypothesis since support thus far has come from data on primates. This study was the first to investigate STFP in a species from the Feliformia suborder. Additionally, finding more evidence that spotted hyenas have advanced cognitive abilities is essential for researchers and zoo personnel who work with spotted hyenas in captivity.

Doctor of Philosophy / Department of Hospitality Management and Dietetics / Chihyung Ok, Deborah D. Canter / This study sought to apply the concepts of ‘perceived value’ and ‘customer share’ (of visits) to full-service restaurant settings for the first time. Given the strong ‘experiential nature’ of foodservice, the perceived value concept adopted in this study involved an ‘experiential view’ of the dining experience. Further, the customer share concept was expected to have implications for the foodservice context, given the multi-loyalty nature of restaurant customers. With the first conceptual model, this study sought to verify the effect of perceived value on customer share of visits in a full-service restaurant context, using a dimension-level value approach and positing customer satisfaction and brand preference as mediators between them. The conceptual model was tested based on responses from 299 general U.S. full-service restaurant customers, using a confirmatory factor analysis and structural equation modeling. The test results revealed that among four value dimensions, excellence (in food and service) and customer return on investment had dominant effects on customer satisfaction and brand preference whereas playfulness had a significant moderate effect only on brand preference; aesthetic appeals did not have significant effects on either. Affected by perceived value, customer satisfaction significantly enhanced brand preference and in turn brand preference contributed to customer share of visits and fully mediated the effect of customer satisfaction on customer share of visits. In essence, the findings highlight the significant antecedent role of perceived value in customers’ satisfaction and brand preference formation, and the pivotal role of customer brand preference in customers’ purchase decision process. With the second conceptual model, this study sought to reveal the direct effect and/or moderating effects of contingency variables in relation to customer share of visits in a fullservice restaurant context. The hypotheses included in the conceptual model were tested based on responses from 291 general U.S. full-service restaurant customers, using a confirmatory factor analysis and a series of (moderated hierarchical) regression analyses. The test results indicated that the direct effects of social switching costs, lost benefits costs, procedural costs, and intrinsic inertia were positive whereas that of intrinsic variety-seeking was negative on customer share of visits. In addition, consumer involvement and perceived brand heterogeneity were found to enhance the effect of brand preference on customer share of visits. The effects of the contingency variables appear to work by influencing the number of brands in customers’ consideration sets and/or leading customers to allocate a greater share of visits to a particular brand in a given number of brands in consideration sets.

Thesis (LLD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The various constructions of rights of pre-emption encountered in South African case law all have some merit. This is confirmed by the multiplicity of types of preference contracts encountered in German law especially. The tendency of South African courts and writers to portray one approach as the only correct one to the exclusion of all other views, results in tension and confusion, all the more because of the failure to investigate the relevant policy considerations comprehensively. The confusion is compounded by what amounts to a breakdown of the system of precedents with judgments being based on incorrect interpretations of previous decisions and with scant regard for contrary decisions. No certainty exists regarding the construction of the contractual right of pre-emption in Roman and Roman-Dutch law, nor is it clear what figure or figures were received into South African law. The Germanic concept of tiered ownership that forms the historical basis for the Oryx remedy, does not form part of our law. This accounts for the difficulty that courts and writers have in explaining this remedy in terms of Romanist terminology, and the resort to the language of fiction. German law and English law, relied upon in South African case law, do not support a uniform construction of all rights of pre-emption as creating an enforceable duty to make an offer upon manifestation of a desire to sell. The almost unanimous support of US courts for a remedy by which the holder can ultimately obtain performance of the main contract upon conclusion of a contract with a third party, challenges the hypothesis suggested by German law that the default construction of preference contracts should be the bare preference contract which only creates a negative obligation. The very cryptic way in which rights of pre-emption are normally drafted, makes it difficult to even identify the main purpose of the parties. It is therefore not easy to classify preference contracts into the different types identified in this study as notional possibilities. A default regime is therefore highly desirable in the interest of legal certainty. The choice of a default regime should be made on the basis of recognised policy considerations, particularly on the basis of an equitable balancing of typical parties' interests and in view of communal interests balanced against the demand for legal certainty. The choice of default regime cannot be based merely on historical authority or precedent (which is in any event unclear in the present context) or unsubstantiated claims that one model is more logical or commercially useful than another. When rules are chosen as the default regime, these rules must, as far as possible, be reconciled with the existing conceptual structure of our law to prevent contradictions and inconsistencies. A policy analysis reveals that three default types of preference contract should be recognised, each with a clearly delineated field of application. Firstly, where the agreement allows the grantor to contract with a third party, the holder has the right to contract with the grantor at the terms agreed with the third party. Such a preference contract can therefore be regarded as an option conditional upon conclusion of a contract with a third party. Such contracts are rare in South Africa. In other cases, the default rule should be that the grantor must first give the holder an opportunity to contract before he contracts with a third party. The default construction of this latter type of preference contracts depends on whether the preference contract itself predetermines the main contract price. If so, the holder has a right or option to contract at that price upon any manifestation of a desire to conclude the relevant type of contract. However, where the preference contract does not predetermine the price, or refers to a price that the grantor would accept from third parties, any manifestation of a desire to sell should not be sufficient to trigger the holder's right. The grantor and society have an interest in having her freedom to negotiate with third parties to obtain the best possible price curtailed as little as possible. In such cases, the default rule should be that the holder is only entitled to conclusion of the main contract upon breach in the form of a contract with or offer to a third party. The default rule should also be that such preference contracts - which will be treated as ordinary preference contracts - only terminate upon the grantor actually contracting with and performing to a third party within a reasonable time after the holder declined the opportunity to match those terms, and provided the identity of the third party was disclosed to the holder on request. The holder therefore cannot lose his preferential right by a rejection of an outrageously high offer by the grantor. Options and preference contracts are closely related and overlapping concepts. The type of preference contract that grants a conditional right to contract can often be understood as a conditional option (or at least as a conditional option subject to a resolutive condition that the grantor does not want to contract anymore). The traditional distinction between options and rights of first refusal can only be maintained in respect of some types of preference contracts. These are negative or bare preference contracts which only give rise to remedies aimed at restoring the status quo ante the breach, as well as those preference contracts creating conditional rights to contract which courts refuse to treat as conditional options because their wording implies a duty to make or accept an offer, or because the requirement of certainty precludes them from being options. / AFRIKAANSE OPSOMMING: Die verskillende konstruksies van voorkoopsregte aanvaar III Suid-Afrikaanse beslissings het almal meriete. Dit word bevestig deur die verskillende tipes voorkoopskontrakte wat veral in die Duitse reg erken word. Die neiging van Suid- Afrikaanse howe en skrywers om een benadering as die enigste korrekte een te tipeer veroorsaak spanning en onsekerheid, des te meer weens die versuim om die relevante beleidsoorwegings deeglik te ondersoek. Boonop is die presedentestelsel telkens verontagsaam deur verkeerde interpretasies van vorige uitsprake en deurdat teenstrydige uitsprake bloot geïgnoreer is. Geen sekerheid bestaan oor die konstruksie van die kontraktuele voorkoopsreg in die Romeinse of Romeins-Hollandse Reg nie. Dit is ook nie duidelik watter figuur of figure in die Suid-Afrikaanse reg geresipieer is nie. Die Germaanse konsep van gesplitste eiendomsreg wat die historiese basis van die Oryx-meganisme daarstel, vorm nie deel van ons reg nie. Dit verduidelik hoekom howe en skrywers sukkel om dié remedie te verduidelik aan die hand van Romanistiese verbintenisreg-terminologie, en die gevolglike gebruikmaking van fiksie-taal. Die Duitse en Engelse reg waarop gesteun is in Suid-Afrikaanse regspraak, steun nie 'n uniforme konstruksie van alle voorkoopsregte as behelsende 'n afdwingbare plig om 'n aanbod te maak by enige manifestasie van 'n begeerte om te verkoop nie. Die byna eenparige steun van Noord-Amerikaanse howe vir 'n remedie waarmee die voorkoopsreghouer uiteindelik prestasie van die substantiewe kontrak kan kry by sluiting van 'n kontrak met 'n derde, is 'n teenvoeter vir die hipotese gesuggereer deur die Duitse reg dat die verstekkonstruksie van voorkeurkontrakte behoort te wees dat slegs 'n negatiewe verpligting geskep word. Die kriptiese wyse waarop voorkeurkontrakte normaalweg opgestel word, maak dit moeilik om selfs die hoofdoelstelling van die partye te identifiseer. Dit is daarom nie maklik om voorkeurkontrakte te klassifisieer in die verskillende tipes wat in hierdie studie geïdentifiseer is nie. 'n Verstekregime is daarom wenslik in die belang van regsekerheid. Die keuse van verstekregime behoort gemaak te word op die basis van erkende beleidsoorwegings, spesifiek op die basis van 'n billike balansering van tipiese partybelange en in die lig van gemeenskapsbelange gebalanseer teen die vereiste van regsekerheid. Die keuse van verstekregime kan nie gebaseer word bloot op historiese gesag en vorige beslissings nie (wat in elk geval in die huidige konteks onduidelik is). Dit kan ook nie gebaseer word op ongemotiveerde aansprake dat een model meer logies of kommersieël bruikbaar as 'n ander is nie. Wanneer verstekreëls gekies word moet dit, sover moontlik, versoen word met die bestaande begrippe-struktuur van ons reg om teenstrydighede in die sisteem te vermy. 'n Beleidsanalise laat blyk dat drie verstektipes voorkeurkontrakte erken behoort te word, elk met 'n duidelik afgebakende toepassingsveld. Eerstens, waar die ooreenkoms toelaat dat die voorkeurreggewer eers met 'n derde party kontrakteer, het die voorkeurreghouer 'n opsie om te kontrakteer op die terme ooreengekom met die derde. Die voorkeurkontrak kan daarom beskou word as 'n opsie onderhewig aan die voorwaarde van sluiting van 'n kontrak met 'n derde. Sulke kontrakte is raar in Suid- Afrika. In ander gevalle behoort die verstekreël te wees dat die voorkeurreggewer eers die houer 'n geleentheid moet gee om te kontrakteer voordat sy met 'n derde 'n kontrak aangaan. Die verstekkonstruksie van hierdie laasgenoemde tipe voorkeurkontrak hang daarvan af of die voorkeurkontrak self die substantiewe kontraksprys vasstel. Indien wel het die houer die reg of opsie om te kontrakteer teen daardie prys by enige manifestasie van 'n begeerte om die spesifieke soort kontrak te sluit. Maar waar die voorkeurkontrak nie die prys vasstel nie, of verwys na 'n prys wat die gewer sou aanvaar van 'n derde, behoort enige manifestasie van 'n begeerte om te kontrakteer nie genoeg te wees om die houer se reg afdwingbaar te maak nie. Die voorkeurreggewer en die gemeenskap het 'n belang daarby dat die gewer se vryheid om met derdes te onderhandel so min as moontlik beperk word sodat sy die beste moontlike prys kan kry. In sulke gevalle behoort die verstekreël te wees dat die houer slegs geregtig is op die voordeel van die substantiewe kontrak by kontrakbreuk in die vorm van 'n kontrak met of aanbod aan 'n derde. Die verstekreël behoort ook te wees dat sulke voorkeurkontrakte in beginsel slegs beëindig word wanneer die voorkeurreggewer inderdaad kontrakteer met en presteer aan 'n derde binne 'n redelike tyd nadat die voorkeurreghouer die geleentheid gegee is om daardie terme te ewenaar. Dit behoort ook vereis te word dat die identiteit van die derde aan die houer geopenbaar word op sy versoek. Die houer kan dus nie sy voorkeurreg verloor deur nie-aanvaarding van 'n belaglik hoë aanbod deur die voorkeurreggewer nie. Opsies en voorkeurkontrakte is oorvleulende konsepte. Die tipe voorkeurkontrak wat 'n voorwaardelike reg om te kontrakteer verleen kan dikwels verstaan word as 'n voorwaardelike opsie (of minstens as 'n voorwaardelike opsie onderhewig aan 'n ontbindende voorwaarde dat die gewer glad nie meer wil kontrakteer nie). Die tradisionele onderskeid tussen opsies en voorkeurregte kan slegs behou word tov sommige voorkeurkontrakte. Hulle is die "negatiewe" voorkeurkontrakte, wat slegs aanleiding gee tot remedies gemik op herstel van die status quo ante kontrakbreuk sowel as daarde voorkeurkontrakte wat voorwaardelike regte om te kontrakteer skep wat howe weier om as voorwaardelike opsies te behandelomdat hulle bewoording wys op 'n plig om 'n aanbod te maak of te aanvaar, of omdat die vereiste van sekerheid hulle verhoed om opsies te wees.

Thesis (MSc (Conservation Ecology and Entomology))--Stellenbosch University, 2009. / ENGLISH ABSTRACT: In 2005, six white rhinoceros (Ceratotherium simum) were reintroduced into Pafuri, in the far northern section of Kruger National Park (KNP), South Africa, as part of a large mammal reintroduction project. All six individuals were fitted with horn radio transmitters. Rhinos have been absent from Pafuri for over a century, and this project aimed to establish a breeding nucleus in the area. The aim of this study was to monitor post-release movement and habitat use of these animals within the 203 km2 study area and assess the short term success of the re-introduction project as well as the suitability of the five landscape types in Pafuri as a habitat for white rhinoceros. Habitat suitability and selection was assessed at two ecological hierarchical scales: 1) landscape system, analysed further down to the spatial scale of range and territory establishment, and 2) feeding station for diet selection. Rhinos were tracked for 12 months and a database of 719 sighting records was compiled. These data were used to determine the utilisation of and preference between the Pafuri landscape types, using preference indices that compare utilisation versus availability. An a-LoCoH nonparametric kernel method was used to calculate home ranges and utilisation distributions of each rhino. Feeding surveys were attempted by backtracking along fresh rhino feeding paths and recording the grass species present and eaten in 0.7 m x 0.7 m quadrats. Faecal samples were collected and analysed using microhistological techniques and dietary composition was assessed for each rhino. Landscape preference analyses showed that the rhinos favoured Colophospermum mopane Shrubveld on calcrete in the dry season, and the Punda Maria Sandveld in the wet season. The territory establishment of the dominant bull was substantially larger (44.8 km²) than those of adult male rhinos in the rest of KNP. Ranging areas of the mature females (17 – 25.4 km²), were consistent with sizes of previous studies. The two sub-adults ranged far more extensively, establishing an 84.1 km² annual range during the study period. The annual diet consisted of mostly perennial grass species, with moderate grazing value species dominating for most of the year. Dietary analyses showed that Schmidtia pappophoroides, Eragrostis superba, Enneapogon cenchroides, Cenchrus ciliaris and Stipagrostis uniplumis were the primary grass species consumed. vii This study demonstrated that the Pafuri rhinos are behaving similarly to rhinos established in other areas, with movements around the landscapes being primarily influenced by rainfall and permanent water sources, and the high quality grazing that is more abundant in the wet season. Their range and territory sizes were inevitably large, for a low density area, but not uncommonly so. The most significant outcome of this study was the preference shown for the Colophospermum mopane Shrubveld on calcrete landscape that is classed as unique within South Africa, and was also ranked as ‘avoided’ by the earlier KNP studies into landscape preferences of rhinos. The grass cover in Pafuri, although sparse and very dry, contained a diversity of low to high grazing value grasses that the rhinos appeared to exploit to the best of their ability. The abundance of moderate grazing value species in their diets, and the low number of low grazing value species suggests that they are maximising the opportunities to graze on nutritious grasses when they are available. Our findings suggest that the Pafuri area is suitable for the establishment of a small breeding nucleus of white rhinos. The abundance of permanent water, in the form of springs, is a great advantage however, the potential for bush encroachment into grasslands in areas of such low rainfall needs to be considered if the population continues to grow at the current rate. The birth of two new calves in 2008 confirms that these rhinos have settled and adapted to their new habitat, and is a very promising sign for the future of this increasing subpopulation. / AFRIKAANSE OPSOMMING: In 2005 is ses wit renosters (Ceratotherium simum) hervestig in Pafuri in die noordelike gedeelte van die Kruger Nasionale Park (KNP), Suid-Afrika, as deel van ‘n groot soogdier hervestigings projek. Al ses individue is gemerk met horing radioseintoestelle. Renosters kom vir al meer as ‘n honderd jaar nie meer in Pafuri voor nie en hierdie projek was daarop gemik om ‘n teel-nukleus in hierdie gesied te vestig. Die doel van hierdie studie was om die verspreiding van die renosters na loslating en habitat-gebruik binne die 203 km2 studie-omgewing te monitor, om die korttermyn sukses van die hervestigings program te evalueer en ook te kyk na die gepastheid van die vyf landskap-tipes in Pafuri as ‘n geskikte habitat vir die wit renosters. Habitatgepastheid en seleksie is geëvalueer volgens twee ekologiese hiërargiese skale: 1) landskapsisteem, wat in meer resolusie tot die ruimtelike skaal van reikwydte en omgewingsvestiging geanaliseer is, en 2) voedings-stasie vir dieet-seleksie. Renosters is vir 12 maande gevolg en ‘n databasis wat 719 waarneming-rekords bevat, is opgestel. Laasgenoemde data is gebruik om die gebruik en voorkeur vir die Pafuri landskap tipes te bepaal met behulp van voorkeur-indikators wat die gebruik met beskikbaarheid vergelyk het. ‘n a-LoCoH nie-parametriese kern metode is gebruik om die reikwydte en gebruiksverspreidings van elke renoster te bereken. Voedingsopnames is gedoen deurdat vars renoster voedings-paadjies terugwaarts gevolg is en die grasspesies teenwoordig en waarop gevoed is, in 0.7 m x 0.7 m kwadrante te bepaal. Mismonsters is versamel en geanaliseer deur gebruik te maak van mikro-histologiese tegnieke en voedingswaarde-samestellings is vasgestel vir elke renoster . Landskapsvoorkeur analises dui daarop dat die renosters in die droë seisoen Colophospermum mopane struikveld wat op kalkreet groei verkies en die Punda Maria Sandveld in die reën seisoen. Die terrein vestiging van die dominanate bul was aansienlik groter (44.8 km²) in vergelyking met die volwasse bul renosters in die res van die KNP. Reikwydte van die volwasse koeie (17 – 25.4 km²) was ooreenstemmend met dié van vorige studies. Die reikwydte van die twee subvolwassenes het baie meer gevarieer, deurdat ‘n 84.1 km² jaarlikse reikwydte gedek was binne die studie periode. Die jaarlikse dieet het meestal bestaan uit meerjarige ix grasspesies, met spesies met matige weidingswaarde wat oorheers vir meeste van die jaar. Voedingswaarde analises dui daarop dat Schmidtia pappophoroides, Eragrostis superba, Enneapogon cenchroides, Cenchrus ciliaris en Stipagrostis uniplumis die primêre gras spesies was waarop gewei word. Die studie het bewys dat die Pafuri renosters soortgelyke gedragspatrone vertoon het as renosters in ander gevestigde gebiede, deurdat bewegings binne die landskap hoofsaaklik beïnvloed word deur reënval en permanente waterbronne, asook die hoë gehalte weidingsbronne beskikbaar gedurende die reën seisoen. Hulle reikwydte- en terrein-groottes was uiteraardelik groot vir ‘n lae-digtheid areas, maar dit is nie buitengewoon nie. Die mees betekenisvolle gevolgtrekking van die studie was die voorkeur vir die Colophospermum mopane struikveld op kalkreet landskappe wat beskou word as uniek aan Suid-Afrika, en wat ook beskou was as ‘vermy’ deur vroër KNP studies tov. landskap voorkeure spesifiek vir renosters. Die grasbedekking in Pafuri, alhoewel yl en baie droog, het tog oor ‘n verskeidenheid grasse beskik wat van lae tot hoë weidings waarde het, en wat die renosters tot die beste van hulle vermoë benut het. Die oorvloedige teenwoordigheid van beide spesies met matige weidingswaarde in hulle dieët en die lae hoeveelheid van spesies met lae weidingswaarde, impliseer dat hulle die geleentheid om op voedingsryke grasse te voed ten volle benut wanneer dit beskikbaar is. Ons resultate dui daarop dat die Pafuri omgewing geskik is vir die vestiging van ‘n klein teel-nukleus van wit renosters. Die oorvloedige teenwoordigheid van permanente waterbronne in die vorm van fonteine is ‘n groot voordeel, maar die kans vir bosindringing in hierdie grasveld-gebiede met lae reënval moet oorweeg word sou die populasie aanhou toeneem teen die huidige tempo. Die geboorte van twee nuwe kalfies in 2008 staaf die moontlikheid dat die renosters gevestig en aangepas het in hulle nuwe habitat, wat ‘n baie belowende teken is vir die toekoms van die groeiende subpopulasie.

Thesis (MSc (Conservation Ecology and Entomology))--Stellenbosch University, 2009. / ENGLISH ABSTRACT: An understanding of the interactions of herbivores, plant nutrients and soil properties is crucial for grazing management. Of particular interest are plant palatability and herbivore grazing preferences. These aspects, the focus of this thesis, were studied in a Swartland Shale Renosterveld and Swartland Alluvium Fynbos mosaic in the Western Cape of South Africa. This vegetation is classified as critically endangered due to the transformation of its landscape in favour of agricultural production and urban settlement. Pre-colonial herbivore vertebrates were hunted out by 1700, leading to a sparse knowledge of the early dynamics of the vegetation. However, currently game farmers and landowners are re-introducing selected species into the area. Thus, managers require knowledge on how to implement practical guidelines for best-practice grazing management. This study investigates, firstly, the relationship between plants and animals. This included seasonal assessment of seed germination from dung of bontebok and eland; the effect of stocking rates on plant palatability (crude protein, crude fibre, crude fat, moisture, tannin and mineral) of herbage was studied with the aim to understand how palatability influences herbivore forage decisions. Secondly, this study looked at how stocking rates influence soil nutrients (nitrogen, phosphorus), and others soil properties such as pH and soil moisture. The distribution of alien grasses was facilitated by grazers. About 58 % of grasses germinated from the dung of eland and Bontebok were alien species. Additionally, there was significant variation in palatability related to grazing pressure and plant maturity between sites and over seasons. Grasses on the high grazing site had higher carbohydrate (3%-5% higher) and protein content (1%-5% higher) than at the least grazed site. Mature grasses contained less water (10%-20%), but no obvious variation in tannin concentration than immature grasses. However, species such as Ficinia sp. showed variations with grazing pressure and maturity. Ficinia sp. on the high grazing site had higher tannin concentration (5mg/ml-22mg/ml) and crude protein (4%-9%) than at the least grazed site. When the plant ages, tannin concentration increase (ranging from 15% to19% higher). Two types of plant were recoreded according to their chemical response following grazing pressure. These types are 1) plants that are grazing tolerant and which produce more carbohydrate when grazed and 2) plants that are grazing intolerant under high grazing pressure and which produce chemical defence compounds such as tannin to deter herbivores attacks. The results indicate that in fynbos and renosterveld, the relationship between preference and plant chemical compounds is not consistent since no IV patterns emerged to explain what compounds drive preference. A combination of chemical compounds may be the reason for the selection by the grazers; alternatively, other compounds not included in the study may influence the forage selection by an herbivore. The second part of the study showed that stocking rates appeared to have a significant effect on soil properties investigated. Soil moisture was significantly affected by the stocking rate in autumn. The high grazing intensity site had the lowest soil moisture especially in autumn (10% lower than the control site), likely due to heavy trampling and soil compaction. pH was the lowest at the high grazing intensity site in all seasons compared to the control site. Likely reasons were the high deposition of nitrogen through dung and urine deposition, high removal of basic cations and animal exportation through hunting activities. Lastly, grazing maintains inorganic nitrogen at stable levels regardless of seasonal changes and increases the concentration of phosphorus especially under high grazing pressure compare to less grazed sites. The grazing dynamics of Swartland Shale Renosterveld - Swartland Alluvium Fynbos mosaic system are complex and multifaceted. Farmers need to pay attention to the nutritional status of plant species grazed to know whether they meet the nutritional requirements of the game in the area. Overstocking should be avoided in this system as it triggers the production of tanniferous compounds that could decrease the survivorship of herbivores. Moderate grazing 0.09 LAU/ha pressure provides the best stocking rates for effective grazing management. / AFRIKAANSE OPSOMMING: Vir suksesvolle weidingsbestuur is dit noodsaaklik om die interaksie tussen herbivore, plantvoedingstowwe en grondeienskappe te verstaan. Van besondere belang is plantsmaaklikheid en herbivore se weidingsvoorkeure. Hierdie aspekte, wat die fokus van hierdie tesis is, is bestudeer in ‘n Swartland Shale Renosterveld en Swartland Alluvium Fynbos-mosaïek in die Wes-Kaap Provinsie van Suid-Afrika. Hierdie plantegroei word as kritiek bedreigd geklassifiseer weens die transformering van sy landskap ten gunste van landbou-aktiwiteite en stedelike vestiging. Pre-koloniale herbivoor vertebrata is teen 1700 deur jagters uitgeroei, wat gelei het tot min kennis oor die vroeë dinamiek van die plantegroei. Wildsboere en grondeienaars is egter besig om geselekteerde spesies in die area te hervestig. Bestuurders moet dus weet hoe om praktiese riglyne vir beste-praktyk weidingsbestuur te implementeer. Hierdie studie ondersoek eerstens die verhouding tussen plante en diere. Dit sluit seisoenale evaluering van saadontkieming uit die mis van bontebokke en elande in; die effek van veegetalle op plantsmaaklikheid (ruproteïen, ruvesel, ru-vet, vogpeil, tannien en minerale) van die weiveld is bestudeer om vas te stel hoe plantsmaaklikheid herbivore se weidingsbesluite beïnvloed. Tweedens het die studie die invloed van veegetalle op grondvoedingstowwe (stikstof, fosfor) ondersoek, asook ander grondeienskappe soos pH en grondvogpeile. Die verspreiding van uitheemse grasse is deur weidende diere gefassiliteer. Ongeveer 58% van alle grasse wat uit die mis van elande en bontebokke ontkiem het, was uitheemse spesies. Verder was daar beduidende variasie in plantsmaaklikheid verwant aan beweidingsdruk en plantvolwassenheid tussen verskillende persele en oor seisoene. Grasse op die hoogs beweide persele het 3%-5% hoër koolhidraatinhoude en 1%-5% hoër proteïeninhoude gehad as die minder beweide persele. Volwasse grasse het 10%-20% minder water bevat as onvolwasse grasse, maar het nie in terme van tannienkonsentrasie van die onvolwasse grasse verskil nie. Spesies soos Ficinia sp. het variasies getoon met beweidingsdruk en volwassenheid. Ficinia sp. het op die hoog-beweide perseel ‘n hoër tannienkonsentrasie (5mg/ml-22mg/ml) en meer ruproteïen (4%-9%) gehad as op die minste beweide perseel. Wanneer die plant verouder, verhoog die toename in tannienkonsentrasie (met tussen 15% en 19%). Twee tipes plante is aangeteken volgens hul chemiese response ná beweidingsdruk. Hierdie tipes is 1) plante wat beweidingstolerant is en wat meer koolhidrate produseer wanneer hulle as weiding dien en 2) plante wat onder hoë beweidingsdruk beweidingsintolerant is en wat chemiese verbindings VI soos tannien produseer om herbivooraanvalle af te weer. Die resultate dui aan dat die verhouding tussen voorkeur en plante se chemiese verbindings nie konstant bly in fynbos en renosterveld nie, aangesien geen patrone na vore getree het wat kon verklaar watter verbindings bepalend is vir voorkeur nie. ‘n Kombinasie van chemiese verbindings mag die rede wees waarom die herbivore sekere plante verkies; alternatiewelik mag ‘n herbivoor se plantseleksie beïnvloed word deur chemiese verbindings anders as dié wat in hierdie studie ondersoek is. Die tweede deel van die studie het aangetoon dat veegetalle blyk ‘n beduidende invloed te hê op die grondeienskappe wat ondersoek is. Grondvogpeile is in die herfs beduidend beïnvloed deur die veegetalle. Die perseel met die hoë beweidingsintensiteit het die laagste grondvogpeil gehad, veral in die winter (10% laer as dié van die kontrole-perseel), waarskynlik weens erge getrappel en grondkompaktering. Vergeleke met die kontrole-perseel was pH die laagste op die perseel met die hoë beweidingsintensiteit, in alle seisoene. Waarskynlike redes hiervoor is die hoë neeerslag van stikstof deur mis- en uriene-neerslae, hoë verwydering van basiese katione en dierevervoer wat deur jagaktiwiteite teweeg gebring word. Laatstens behou weiding anorganiese stikstof teen stabiele vlakke ongeag van seisoenale veranderinge en toenames in die konsentrasie van fosfor, veral onder hoë beweidingsdruk vergeleke met minder beweide persele. Die weidingsdinamiek van die Swartland Shale Renosterveld - Swartland Alluvium Fynbosmosaïeksisteem is kompleks en veelvlakkig. Boere behoort aandag te skenk aan die voedingstofstatus van die plantspesies wat as weiding dien, sodat hulle kan weet of die voedingsbehoeftes van die wild in die omgewing bevredig word. Die aanhou van te veel vee in hierdie sisteem behoort vermy te word aangesien dit as sneller dien vir die produksie van tannienbevattende verbindings wat die oorlewingsvermoë van herbivore kan verlaag. Matige beweidingsdruk (0.09 LAU/ha) bied vir effektiewe weidingsbestuur die beste veegetalle.

This thesis, motivated by my reflections about the failings of monetary policy implementation as a cause of the sub-prime crisis, attempts to answer the following inquiries: (i) whether interest rates have played a major role in generating the house price fluctuations in the U.S., (ii) what are the effects of accommodative monetary policy on the economy given banks' excessive risk-taking, and (iii) whether an optimal monetary policy rule can be found for curbing credit-driven economic volatilities in the model economy with unconventional transmission channels operating. By using a decomposition technique and regression analysis, it can be shown that short-term interest rates exert the most potent influence on the evolution of the volatile components of housing prices. One possible explanation for this is that low policy rates for a prolonged period tend to encourage bankers to take on more risk in lending. This transmission channel, labelled as the risk-taking channel, accounts for the gap to some extent between the forecast and the actual impact of monetary policy on the housing market and the overall economy. A looser monetary policy stance can also shift the preference of economic agents toward housing as theoretically and empirically corroborated in the context of choice between durable and nondurable goods. This transmission route is termed the preference channel. If these two channels are operative in the economy, policy makers need to react aggressively to rapid credit growth in order to stabilize the paths of housing prices and output. These findings provide meaningful implications for monetary policy implementation. First of all, central bankers should strive to identify in a timely fashion newly emerging and state-dependent transmission channels of monetary policy, and accurately assess the impact of policy decisions transmitted through these channels. Secondly, the intervention of central banks in the credit or housing market by adjusting policy rates can be optimal, relative to inaction, in circumstances where banks' risk-taking and the preference for housing are overly exuberant.