Researchers and practitioners are increasingly interested in entrepreneurship as a means to fight youth unemployment and to improve financial stability at higher ages. However, only few studies so far have examined the association between age and entrepreneurial activity. Based on theories from the lifespan psychology literature and entrepreneurship, we develop and test a model in which perceived opportunities and skills explain the relationship between age and entrepreneurial activity. We analyzed data from the 2013 Global Entrepreneurship Monitor (GEM), while controlling for gender and potential variation between countries. Results showed that age related negatively to entrepreneurial activity, and that perceived opportunities and skills for entrepreneurship mediated this relationship. Overall, these findings suggest that entrepreneurship research should treat age as a substantial variable.

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Perhaps the most important single finding in the field of emotional aging has been that the overall quality of affective experience steadily improves during adulthood and can be maintained into old age. Recent lifespan developmental theories have provided motivation- and experience-based explanations for this phenomenon. These theories suggest that, as individuals grow older, they become increasingly motivated and able to regulate their emotions, which could result in reduced negativity and enhanced positivity. The objective of this paper is to expand existing theories and empirical research on emotional aging by presenting a discrete emotions perspective. To illustrate the usefulness of this approach, we focus on a discussion of the literature examining age differences in anger and sadness. These two negative emotions have typically been subsumed under the singular concept of negative affect. From a discrete emotions perspective, however, they are highly distinct and show multidirectional age differences. We propose that such contrasting age differences in specific negative emotions have important implications for our understanding of long-term patterns of affective well-being across the adult lifespan.

Menopause is characterized by prolonged lifespan beyond the point of reproductive cessation. Defined so that at least 25% of adulthood is nonreproductive, humans and some toothed whale species are the only groups that have been found to exhibit menopause. Menopause is a puzzling trait that seems to contradict classical evolutionary theory that equates selection operating on reproduction to selection operating on survival. I created two computational models to gain better understanding of the evolution of menopause. The first model explored why menopause is not observed in elephants despite their being characterized by key features in common with menopausal species, specifically offspring care from older females and longevity. Simulations allowed testing the effects of varying age at reproductive cessation and levels of offspring care, modeled by decreases in interbirth intervals. I found that hypothetical populations with greatest post-reproductive lifespans, characterized by longer interbirth intervals and earlier reproductive cessation, were most likely to be out-competed by contemporary elephants. Conversely, hypothetical populations that were most reproductively competitive, those with shorter interbirth intervals and older ages of reproductive cessation, returned post-reproductive lifespans that failed to meet the 25% post-reproductive lifespan criterion for menopause. I identified a small region in the parameter space where populations that were both menopausal and reproductively competitive evolved, but the majority of that region corresponds to biologically unrealistic scenarios. The scenario that is most feasible involves an interbirth interval of 4 years and an age at reproductive cessation of 40 years. The second model studied how menopause might have evolved in humans through a behavioural strategy of ending reproduction early to avoid risk of aneuploidy later in life and diverting resources toward extant kin. I found that populations that ceased reproduction earlier and exhibited greater post-reproductive lifespan returned lower reproductive success. The model also demonstrated that the aneuploidy avoidance behaviour is most successful when reproduction ends at approximately age 50. These concepts have never been explored computationally before, so these experiments contribute a novel simulation-based perspective to the growing body of knowledge surrounding the origin and evolution of menopause. / Thesis / Master of Science (MSc) / Menopause can be defined generally for a group as a life history characterized by prolonged post-reproductive lifespan. Defined specifically so that at least 25% of adulthood is nonreproductive, menopause has been recorded in only humans and some species of toothed whales. This trait presents an evolutionary puzzle, as it appears to contradict classical evolutionary theory, which suggests that reproduction should continue until the end of life. In this thesis, I use computational modeling to explore why elephants have not evolved menopause despite sharing key features with menopausal species and how aneuploidy might have contributed to the evolution of menopause in humans.

Episodic memory binds together the people, objects, and locations that make up the specific events of our lives, and allows the recall of our past in the service of current and future goals. Recent models of memory have posited that the hippocampus instantiates computations critical for episodic memory including mnemonic discrimination, relational binding, and holistic retrieval. Collectively, this set of studies aim to chart the ontogeny of each key components of episodic memory. We found robust improvements in children’s abilities to form complex relational structures and to make fine-grained discrimination for individual items from age 4 to age 6. However, relational memory dependent on context discrimination appears to follow a more protracted development. Furthermore, relational binding and mnemonic discrimination (item and context levels) undergo age-related decrements in senescence. Despite relatively poor relational binding capabilities, children as young as age 4 are able to retrieve multi-element events holistically, such as successfully retrieving of one aspect of an event predicts the retrieval success of other aspects from the same event. Critically, the degree of holistic episodic retrieval increases from age 4 to young adulthood. This multi-process approach provides important theoretical insights into lifespan profile of episodic memory. / Psychology

A fundamental question in language research is the extent to which linguistic and cognitive systems interact. The aim of this thesis is to explore that relationship across new contexts and over the entire adult lifespan. This work centers on two branches of empirical research: the first is an investigation into the impact of later-life language learning on cognitive ageing (chapters 2-4), and the second examines the cognitive mechanisms underlying communicative perspective-taking from young adulthood into old age (chapter 5). The results of these chapters demonstrate that changes to one's linguistic environment can affect cognitive functions at any age, and similarly age-related changes to cognition can affect linguistic abilities, shedding light on the extent to which language and the brain are intricately connected over the lifespan. In the discussion (chapter 6), I consider how this work contributes new insights to the field, opening the door for future research to explore methods of improving cognitive abilities and linguistic behavior in old age.

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突變生成(mutagenesis)的方式有許多種，其中insertional mutagenesis為果蠅上常使用建立突變株的方式，本篇論文利用p[GawB]隨機插入果蠅genome中產生大量突變株，並篩選出會影響壽命的突變果蠅M2。進一步的實驗發現M2果蠅為Vha16-1基因的突變，並造成其mRNA表現量的下降，且在低卡路里(5% yeast、5% dextrose)與高卡路里(15% yeast、15% dextrose)的環境下homozygous mutant果蠅皆有減少平均壽命的現象。 Vha16-1所表現的蛋白為Vacuolar-type H+-ATPase (V-ATPase)上的subunit c，V-ATPase主要的功能為藉由消耗ATP來運送氫離子，並可調節胞器或胞外腔室的酸鹼平衡。V-ATPase主要表現在果蠅腸道的copper cell上，此細胞的功能類似於哺乳動物的胃壁細胞(parietal cells)，與胃酸的分泌有關，我們發現M2 homozygous mutant果蠅因Vha16-1基因的缺失而有減少腸道酸化的情形發生，符合我們觀察到其在腸道上的表現。此一現象亦在另一株突變果蠅Vha16-1EP2372上加以證實。先前研究顯示果蠅腸道酸鹼平衡的破壞會影響到對養分的吸收，而Vha16-1的缺失亦導致M2果蠅體重與三酸甘油酯的上升，並增加對飢餓的耐受性，而這些代謝上的變化並不會改變M2果蠅對食物的攝取量或者生育能力。綜合這些實驗結果，我們推測Vha16-1基因的缺失會改變腸道功能，並影響果蠅體內代謝的狀態，表現出類似肥胖(obesity)的性狀，而終導致平均壽命的縮短。 / Mutagenesis can be induced by many ways and one of the most common approaches used in Drosophila is insertional mutagenesis. In this study, we screened pGawB insertion lines and identified M2 as a novel mutant with affected lifespan. The mutant allele of M2 carried a pGawB inseration at the 5’ end of the Vha16-1 gene, which caused a reduced Vha16-1 mRNA expression level and a shorten lifespan in homozygous mutants under both low calorie (5% yeast and 5% dextrose) and high calorie (15% yeast and 15% dextrose) foods. Vha16-1 encodes the c subunit of the Vacuolar-type H+-ATPase (V-ATPase) which is known to regulate pH homeostasis by pumping protons across organelle and plasma membranes. V-ATPase is highly expressed by the Copper cells which are located at the Drosophila middle midgut and functionally similar to the gastric acid producing parietal cells in mammals. Along the same line, we found that Vha16-1 pGawB drives GFP reporter was observed along the Drosophila gastrointestinal tract. M2 as well as the other Vha16-1 hypomorphic mutant line, EP2372, also showed reduced midgut acidification. This disrupted pH homeostasis in the Drosophila midgut region may be associated with increased body weight, triglyceride, and starvation resistance that observed in M2 mutants. The feeding behavior and reproductive function, however, were not affected in M2 mutant flies. In summary, our data suggested Vha16-1 deficits may alter normal intestinal function or internal metabolic status that ultimately induces obesity phenotypes with reduced lifespan.