Mental health problems among children and youths are common and have numerous negative consequences for young people and their social network. Therewith, these problems pose a social issue. GPs... Show moreMental health problems among children and youths are common and have numerous negative consequences for young people and their social network. Therewith, these problems pose a social issue. GPs play an important role in early detection and management of these problems. Insight into their clinical decision- making and, as a result, way of working would be helpful to develop methods for providing children and youths with the help they need. Previous literature suggest many doctors(-to-be), of whom some are or will become GPs, have (lived) experience related to mental health problems themselves. Previous studies also suggest having (lived) experience influences GPs’ clinical decision-making, and consequently their way of working. It would have clinical benefits for GPs and patients to explore this process. This thesis is constructed of four different articles, each contributing to answering the main question: ‘How do GPs decide on child and youth mental health problems and what is the influence of their(lived) experience regarding these problems on this decision?’ Article 1: How do GPs make decisions regarding mental health problems in children and youths? For answering this subquestion, a mixed methods design was used: interviews among 14 and an online survey among 15 GPs. GPs were asked about their clinical decision-making process on children and youths with mental health problems using three vignettes describing children and youths with mental health problems representative of clinical practice. The findings suggest GPs differ with regards to their decision- making regarding child and youth mental health problems, and that their decision-making is influenced by factors related to 1) the GP, for example if the GP approaches the problem somatically or psychosocially, if the GP considers themself competent enough to solve the problem with regards to their interest in and knowledge about youth mental health care, 2) the child and its social context, for example if the child or youth has psychiatric (co)morbidity, if the problem is likely to solve itself and if the problem could be assessed as being complex and 3) the GPs’ collaboration with other youth care providers, for example if GPs have existing collaboration agreements with these youth care providers and how they view their collaboration. Article 2: Can GPs’ decisions on child and youth mental health problems be supported by means of a decision-support method?For answering this subquestion, a literature search was conducted to retrieve studies that involved clinical decision support methods for GPs’ clinical decision-making related to mental health problems among children and youths. This systematic review yielded 25 studies on 18 clinical decision-support methods, divided into computer-based methods (such as MyGRaCE), telecommunication methods (such as CAP PC) and methods with a combination of components related to computer-based methods and telecommunication methods (such as Collaborative care for depression intervention). The article provides insight into (possible) beneficial clinical implications of clinical decision-support methods. These methods could give more insight into possible mental health problems, they could provide structured information which can be used by the GP and/or parents during their next consultation with the child or youth, and they could also decrease time and costs spent by the primary care practice and the GP. There are also less beneficial clinical implications, such as an inability for some computer-based methods to be used in emergency situations, when time is short, problems for children and youths when using computer-based methods because of their mental status, and impediment to discuss certain topics freely because the decision-support method gives too much direction to the consultation. The article describes certain considerations for GPs when choosing a decision-support method, which may indirectly have a positive impact on the implementation of such methods into general practice. For example, the GP can take into account their way of working, user flexibility of the method for the GP, the child/youth and their parent(s) with regards to understandability and ease of use, if the GP already uses a clinical decision-support method, if the GP already has collaboration agreements with youth care providers, as well as their own attitude and knowledge regarding mental health problems among children and youths.Article 3: Do doctors-to-be, among whom future GPs, have (lived) experience regarding mental health problems? Study focused on preclinical medical students.For answering this subquestion, self-report questionnaires were sent to 1311 preclinical medical students of Leiden University Medical Center to measure burnout-, depression- and anxiety-related symptoms. The article concludes that symptoms related to mental health problems are common among preclinical medical students. Burnout-related symptoms were found in 46%, depression-related symptoms in 27% and anxiety- related symptoms in 29% of preclinical medical students. Burnout-related symptoms among preclinical medical students were correlated with a sleep duration of less than 6 hours per night, low happiness and a high need for recovery after a day of study. Depression- and anxiety-related symptoms were mainly correlated with low optimism, low happiness, and a high need for recovery after a day of study. These findings suggest preclinical medical students are at risk to develop mental health problems, which can inspire universities to come up with preventive interventions.Article 4: Do doctors-to-be, among whom future GPs, have (lived) experience regarding mental health problems? Study focused on medical interns.For answering this subquestion, self-report questionnaires were sent to 709 medical interns of the same institution mentioned in article 3 to measure burnout-related symptoms. Burnout-related symptoms were found in 30% of medical interns. Burnout-related symptoms among medical interns were related to low dedication with regards to work, a high work pace and quantity, a high need for recovery after a day of work and low optimism. These correlates could be used to prevent mental health problems among medical interns by making adjustments to the medical curriculum. The articles of this thesis suggest GPs’ decision-making on mental health problems in children and youths is multifactorial and consists of objective and subjective components. Furthermore, decision-making seems to differ between GPs, which may be an explanation why there are a variety of clinical decision support methods. Some clinical decision support methods have been implemented in the context of research into general practice, like MyGRaCE, CHICA, Mobiletype, Youth StepCare, consultation-liason method(between GPs and psychiatrists), telepsychiatry consultation practice and the MC3 Program. A clinical implication is GPs can choose a decision-support method which match their personal style of clinical decision-making. However, the validity, trustworthiness and usability of available methods need to be further explored. A clinical implication with regards to medical students’ mental health comprises universities provide accessible proactive mental support to preclinical medical interns and medical interns, because many do not seek help themselves. Furthermore, universities could stimulate a stigma-reducing educational environment, for example in collaboration with the department of (Child- and Adolescent) Psychiatry. Therefore, medical students could be equipped with effective strategies to cope with mental health problems. Also, they might be made aware of their vulnerability, so that they may know their subjectivity and use their personal experiences in practice. The results of this thesis invite more (longitudinal) research on the diagnostic precision, predictive value and cost-efficiency of clinical decision-support methods. Furthermore, more research is needed on the prevalence of mental health problems among graduated doctors, like GPs, and possible effects of these problems on their way of working, their decision-making and their contacts with patients. Strengths of this thesis include exploration of a relatively unknown research area, namely GPs’ clinical decision-making regarding mental health problems among children and youths. Therefore, this thesis used multiple research methodologies and it used a practical scope. This thesis also contains several limitations, such as inclusion of a small GP population, as well as self-selection bias in the studies on preclinical medical students, medical interns and GPs. Finally, interpretation of the results of this thesis was impeded because the research has been conducted in one university, because cause and effect of results could not always be disentangled and because of low statistical power. Because having mental health problems may influence GPs’ clinical decision-making, one could explore how (future) doctors work, study and relax. Therefore, it is recommended to strive for educating balanced doctors: persons who, in collaboration with their colleagues, are – through reflection – aware of their needs and wants between professional boundaries. Show less
This thesis introduces the concept of "physics-based inverse design", working on the notion that the physical driving forces governing functionality are inherently encoded in independently... Show moreThis thesis introduces the concept of "physics-based inverse design", working on the notion that the physical driving forces governing functionality are inherently encoded in independently parameterized energy functions, which can be resolved through the use of inverse design strategies.The thesis describes the development of EVO-MD, a Python-based implementation of the physics-based inverse design concept. EVO-MD is capable of automatically setting-up, performing, and analyzing molecular dynamics simulations, allowing for the evolutionary optimization of complex and dynamic features in peptides. Examples of such applications include the optimization of lipid composition and curvature sensors, and the development of peptides with antiviral properties. Show less
The early history and development of the historiographical method and theory of “conceptual history” resp. “Historical Semantics”—the latter being the overarching term that includes the... Show moreThe early history and development of the historiographical method and theory of “conceptual history” resp. “Historical Semantics”—the latter being the overarching term that includes the specifically German version of conceptual history (= Begriffsgeschichte)—is still widely unknown. One of the first central protagonists of the beginnings of this now widely appraised historiographical approach was the German-Jewish historian Richard Koebner (1885-1958). As a transnational actor, Koebner was not only part of the specifically German beginnings of Begriffsgeschichte during the Weimar Republic, but he was also—after his forced emigration to Jerusalem and during his retirement-years in London—influential for the development of Historical Semantics in Israel and England. Show less
Acute cardiovascular syndromes, including myocardial infarction or stroke, are the principal cause of death in the Western society. The main underlying pathology of cardiovascular diseases is... Show moreAcute cardiovascular syndromes, including myocardial infarction or stroke, are the principal cause of death in the Western society. The main underlying pathology of cardiovascular diseases is atherosclerosis, which is caused by the accumulation of lipids and inflammatory cells in the vessel wall, in so-called atherosclerotic plaques. Current therapies mainly target the disturbed lipid homeostasis, but recent clinical trials have shown a clear benefit in treating patients with anti-inflammatory drugs. However, more specific targeting is required to avoid unwanted side effects. In this thesis, we have generated a detailed atlas of all the cells present in human atherosclerotic plaques using a novel state-of-the-art technique called single-cell RNA sequencing. This data set can be applied as a powerful tool to select potential drug targets with a functional relevance for atherosclerosis. We showed that the majority of the immune cells in the human atherosclerotic plaque consisted of T cells. Subsequently, we identified a pro-inflammatory population of T cells that likely responds to a plaque-derived antigen, suggesting that atherosclerosis has an autoimmune-like component. Finally, we have applied our single-cell atlas to define and validate targets to intervene with the recruitment and activation of mast cells and other immune cells in atherosclerosis. Show less
Synthetic methodlogy is described, aiding in the synthetic preparation of putative inhibitors of retaining and inverting glycosidases and glycosyl transferases. All constructs are cyclophellitol... Show moreSynthetic methodlogy is described, aiding in the synthetic preparation of putative inhibitors of retaining and inverting glycosidases and glycosyl transferases. All constructs are cyclophellitol-based cyclitols. Show less
This dissertation addresses the dynamic process of the Arab Muslim conquests in Bactria and their socio-political impacts in the region. It covers almost a century from 31–128/651–746. It discusses... Show moreThis dissertation addresses the dynamic process of the Arab Muslim conquests in Bactria and their socio-political impacts in the region. It covers almost a century from 31–128/651–746. It discusses the conquests within the context of the geographical and political complexity of the region. It highlights the local political situation before the Arab Muslims’ arrival and the active role of Bactrian rulers whose cooperation and resistance shaped and reshaped the conquests. In doing so, it combines a broad spectrum of sources. It brings Bactrian, Arabic (and relevant Middle Persian and Sogdian) documents with the literary sources, specifically Arabic narratives related to the conquests and Persian and Chinese reports. It also consults numismatic data, seals and sealings, inscriptions, and archaeological reports. Based on a systematic analysis of these sources, this dissertation shows that the Arab Muslim conquests of Bactria were not simply the results of a series of ‘pre-planned’ military operations initiated and led by the Arab Muslims, as it is often assumed to have been the case. In contrast, the conquests were highly complicated as they were deeply affected by the local and regional political situation that were not considered. The local and regional political competitions in late Sasanian Khurasan pulled the Arab Muslims into the region, where they helped the local rulers to implement their political agendas. However, being in Sasanian Khurasan allowed the Arab Muslims to learn about local political competition, become part of it, create their niche of power, and eventually establish their political domination over the region. The conquests of Sasanian Khurasan, Bactria, Sogdiana and Khwarazm (that formed Umayyad Khurasan) became possible only with the help of some local rulers who viewed the Arab Muslims as powerful allies to overcome their internal or neighbouring rivals. The local rivalries benefited the Arab Muslims the most as they provided space for the expansion and consolidation of Arab Muslim authority in the region in the long term. At the same time, the Arab Muslim settlements in the region marked the beginning of a centuries-long process of Islamicisation in Bactria, out of which the Islamic Balkh has emerged. Show less
This thesis aims to investigate the effect of tripartite interaction between microbial inoculants, the plant, and herbivore insects on the rhizosphere microbiome and volatilome. We investigated the... Show moreThis thesis aims to investigate the effect of tripartite interaction between microbial inoculants, the plant, and herbivore insects on the rhizosphere microbiome and volatilome. We investigated the rhizosphere microbiome and volatilome of tomato plants exposed to insect herbivory and/or inoculated with beneficial microbes known to trigger ISR. First, we reviewed the abiotic and biotic factors that impact the success of ISR microbial inoculants (Chapter 2). Then, we tested microbial inoculants against different stresses and experimental conditions to compare interactions in variable contexts (Chapter 3). Next, we explored the impact of insect herbivory aboveground, on the volatile and microbial belowground compartment. In Chapter 4 we explored root volatiles under stress in two tomato species to evaluate the genotype impact on the stress-induced root volatilome. In Chapter 5, we studied the impact of endosymbiotic fungi arbuscular mycorrhizal fungi (AMF) on root volatiles in an in vitro bioassay and in a greenhouse setup with herbivory-stressed plants. In Chapter 6, we compared the effect of four phylogenetically diverse bacteria and fungi, inoculated as single-species and as a synthetic community, on the rhizosphere microbiome assembly and volatilome in herbivory-stressed plants. Overall, this thesis delves into overlooked interactions providing novel data on belowground plant-microbe interactions. Show less
The dissertation explores the complex interplay between financial scarcity and its psychological effects, shedding light on its impact on decision-making, avoidance behavior, and perceived control.... Show moreThe dissertation explores the complex interplay between financial scarcity and its psychological effects, shedding light on its impact on decision-making, avoidance behavior, and perceived control. Through a series of experiments, we found that financial scarcity increases temporal discounting, indicating a tendency to prioritize immediate gains over future outcomes. A longitudinal study revealed a reciprocal relationship over time between financial scarcity and avoidance behavior, hinting at the existence of a psychological poverty trap. Furthermore, an experiment demonstrated that financial scarcity increases the tendency to delay bill payments. However, evidence regarding attentional disengagement from financial stressors, assessed with an eye-tracker, remained inconclusive. A global survey spanning 51 societies confirmed the negative link between financial scarcity and perceived control, but also uncovered significant cross-cultural variations. Surprisingly, in societies with lower welfare provisions and institutional quality, the negative relationship between financial scarcity and control was weaker. Likewise, collectivist and traditional values seemed to buffer against the negative effect of financial scarcity on control. The dissertation informs about the psychological reality of dealing with problematic household finances and its consequences on decisions. Show less
Climate change is one of the largest challenges faced by humanity. To combat this research into alternatives to fossil fuels is ongoing. Dihydrogen is considered a good alternative fuel, since its... Show moreClimate change is one of the largest challenges faced by humanity. To combat this research into alternatives to fossil fuels is ongoing. Dihydrogen is considered a good alternative fuel, since its burning only forms water. A promising means of acquiring dihydrogen is photocatalysis, which can be driven by sunlight. This involves water oxidation and proton reduction, both half-reactions require a catalyst and photosensitizer, generally metal complexes. The limited aqueous solubility and stability of these complexes poses a challenge in their application. In this thesis we investigated the use artificial metalloenzymes (ArMs) for the catalysis and photosensitization of both half-reactions. ArMs can improve the aqueous solubility of these catalysts and provide a second coordination sphere that can be used to improve the stability and activity. The ArMs in this thesis were prepared using the axial coordination of a catalyst or photosensitizer to a protein via histidine. We set up an effective screening method for this coordination using semi-native PAGE. We then prepared and characterized one of the first ArMs with photocatalytic water oxidation activity. We prepared eight photosensitizing ArMs, of which two also able to catalyse hydrogen evolution. Two of these ArM systems were entirely earth-abundant metal-based and showed good activity. Show less
In this thesis, we describe the potential of cell mechanical phenotyping for immune cell characterization, diagnosis, drug testing, as well as treatment of disease.
This dissertation focused on the neural and behavioral mechanisms underlying adolescent learning and mental health in the context of peers and friends. The neuroimaging findings revealed that... Show moreThis dissertation focused on the neural and behavioral mechanisms underlying adolescent learning and mental health in the context of peers and friends. The neuroimaging findings revealed that reward processing for self and peers rely on common reward-related brain regions, whereas a social brain region (TPJ) showed social specificity to observed outcomes for unfamiliar peers compared to friends. Moreover, typically developing adolescents and adolescents with ADHD show neural sensitivity in reward and salience brain regions towards rewards for themselves, friends and peers compared to losses. There were no group differences in neural processing of (vicarious) outcomes between adolescents with and without ADHD, yet a symptom-level approach showed more neural sensitivity for own compared to friends’ losses in individuals with more inattention symptoms. The behavioral findings indicated that adolescents’ learning performance benefitted from observing the choices and outcomes of peers irrespective of the relationship with this peer. The results did not show effects of friendship (quality) and social status on observational and academic learning, but there was a protective effect of friendship quality on internalizing problems. Taken together, these findings highlight adolescence as a period of observational learning opportunities from different types of peers. Adolescence can also serve as a window of opportunity to improve mental health by fostering high-quality friendships. Show less
The central inquiry of this thesis revolves around how ontology can adequately accommodate the existence of necessary physical relations. Initially, the thesis demonstrates the imperative... Show moreThe central inquiry of this thesis revolves around how ontology can adequately accommodate the existence of necessary physical relations. Initially, the thesis demonstrates the imperative acknowledgment of necessary physical relations by showcasing the failure of Neo-Humean theories. Subsequently, it embarks on an investigation of the foundational explanation of physical necessity. This investigation scrutinizes two distinct accounts of necessary physical relations: dispositionalism and ontological structural realism (OSR), typically perceived as contrasting approaches to elucidating physical necessity. The thesis contends that the individuation regress inherent in dispositionalism compels its alignment with OSR. It then identifies a deficiency within the current OSR framework concerning the elucidation of the relationship between mathematical and physical necessity, attributing this shortfall to OSR's lack of ontological discussion regarding the nature of relations and structures. In response, this thesis endeavors to construct an ontological framework based on the relation of coexistence. This framework is demonstrated to encompass isomorphic counterparts of all mathematical structures within any mathematical reductionist program, as well as the isomorphic counterparts of all physical structures derived from these mathematical foundations. Such a framework facilitates the differentiation between mathematical and physical structures, thereby elucidating the distinction between mathematical and physical necessity. Show less
This dissertation examines the educational positions of children of immigrants in the Netherlands from 1980 to 2020. In particular, the influence of migration background and socioeconomic factors... Show moreThis dissertation examines the educational positions of children of immigrants in the Netherlands from 1980 to 2020. In particular, the influence of migration background and socioeconomic factors on educational positions is studied. Findings reveal substantial progress in education for migrant children overall, especially among the second generation, younger cohorts, and girls with a migrant background, indicating promising upward mobility within the education system for many of these children. The family environment impacts educational outcomes, with socioeconomic background playing a crucial role. Higher parental incomes correlate with higher education levels for children in both the short and long term. Additionally, the living environment affects outcomes such as school dropout rates, especially among boys from migrant backgrounds in larger cities. They are more prone to leaving education prematurely than their female or non-migrant peers. Despite institutional barriers and discrimination within the education system, these children demonstrate an upward trend in education, highlighting the need for further research incorporating discrimination as a factor. Show less
This thesis focuses on the clinical outcomes after Descemet membrane endothelial keratoplasty (DMEK). Chapter 2 describes the suitability of septic donor corneas for transplantation and the... Show moreThis thesis focuses on the clinical outcomes after Descemet membrane endothelial keratoplasty (DMEK). Chapter 2 describes the suitability of septic donor corneas for transplantation and the clinical outcomes after DMEK using septic versus non-septic donor corneas. Chapter 3 aims to analyze the incidence of cataract extraction in eyes that previously underwent DMEK surgery and the effect of the phacoemulsification procedure on the endothelial cell density (ECD) after DMEK. Chapter 4 of the thesis concentrates on the 6-month ECD after DMEK, as it is one of the benchmark parameters for graft performance. In this chapter, the relation between the ECD 6 months after DMEK and its predictive value for 5-year graft survival in FECD eyes are discussed. Chapter 5 evaluates the 10-year graft survival and clinical outcome results of the first 100 eyes that received DMEK. Chapter 6 presents a larger case series of DMEK eyes where the 10-year clinical outcomes and graft survival after DMEK are analyzed based on the surgical indication of the eye and the preoperative severityof FECD. Show less
Mucosal melanomas (MM) are malignant tumours arising from melanocytes located at the mucosal lining of the head and neck region or the respiratory, gastrointestinal, anorectal, or genital tract.... Show moreMucosal melanomas (MM) are malignant tumours arising from melanocytes located at the mucosal lining of the head and neck region or the respiratory, gastrointestinal, anorectal, or genital tract. Due to the low incidence the disease is still poorly understood and management is mostly based on guidelines of cutaneous melanoma (CM). Survival of patients with MM is poor and regardless of stage is worse than that of CM. This is explained by the advanced stage at diagnosis and high recurrence rates of MM. Moreover, whilst immunotherapeutic agents have revolutionized the therapeutic landscape in CM, in MM, the efficacy is low and survival has not improved since the introduction of these therapies.The MM located at the vulva (VMM) account for 60% of the female genital tract MM and together with the head and neck region are the most common locations of MM. In line with the MM located at all other locations, prognosis is poor. Whilst the majority of the patients is diagnosed with local disease, the aggressive course of disease is demonstrated by the high recurrence rates with short time to recurrence with a median overall survival of 33 months. To improve outcomes in MM, there is a critical need for clinical trials specifically designed for this disease and international collaboration. Show less
This thesis starts with a literature review on the observation of aggression, then describes the development and implementation of an Observation Checklist in 2 Dutch Juvenile Justice Institutions ... Show moreThis thesis starts with a literature review on the observation of aggression, then describes the development and implementation of an Observation Checklist in 2 Dutch Juvenile Justice Institutions (JJI) and concludes with two papers researching the added value of data harvested with this tool, both for risk assessment and cultural sensitive assessment. Show less
The growing number of older patients presenting to Emergency Departments (EDs) requires better risk stratification to guide treatment and dispositiondecisions. Therefore, it is essential to... Show moreThe growing number of older patients presenting to Emergency Departments (EDs) requires better risk stratification to guide treatment and dispositiondecisions. Therefore, it is essential to understand the effect of age on the associations between physiological variables and outcomes. More importantly, most risk tools are not age or sex adjusted and are not based on a statistical approach. An age and sex adjusted risk tool could improve risk stratification in the ED.This thesis is divided into three parts and has four aims, regarding ageadjusted interpretation of physiological variables for risk stratification in ED patients, developing a new age- and sex-adjusted risk tool for the hospital, and describing potential bias if risk tools are used for comparing the quality of care among departments. Show less
There is an increasing number of adults who suffer from cardiovascular diseases (CVD). These patients would benefit from a healthy lifestyle, as this improves the prognosis of CVD. However, even... Show moreThere is an increasing number of adults who suffer from cardiovascular diseases (CVD). These patients would benefit from a healthy lifestyle, as this improves the prognosis of CVD. However, even though improving one’s health and lifestyle is the focus of cardiac rehabilitation, CVD patients need support to also maintain a healthy lifestyle after their rehabilitation has ended. Even though the support of a healthcare professional seems to be an important factor in successful lifestyle change, there are barriers that hinder professionals from providing lifestyle support, such as a lack of time or expertise. Since the involvement of healthcare professionals is also not always possible or desirable, it is important to further investigate possibilities to provide patients with a self-help eHealth intervention. In such self-help eHealth interventions, feedback is automatically provided, making the interference of a healthcare professional no longer needed. However, self-help eHealth interventions can suffer from a low uptake and a low level of adherence. This PhD dissertation therefore focuses on (1) mapping out the needs and wishes of both healthcare professionals and CVD patients with regard to (human-supported and self-help) eHealth lifestyle interventions, and (2) investigating if and how self-help eHealth lifestyle interventions could be optimised. Show less
Molecular materials have been a subject of interest in fundamental research and applications for decades, and have been studied as bulk crystals, (thin) films and as individual molecules, due to... Show moreMolecular materials have been a subject of interest in fundamental research and applications for decades, and have been studied as bulk crystals, (thin) films and as individual molecules, due to the large variety in their properties. This dissertation explores pentacene crystals near the two-dimensional limit, i.e. in films of one to a few monolayers, primarily using an experimental technique called Low Energy Electron Microscopy (LEEM). We utilize the interaction of low-energy electrons with the molecular layers to learn about the properties of the layers, and also employ low-energy electrons as an external stimulus to create controlled changes in the properties of the sample. We study the real-time dynamics of growth of pentacene layers on various substrates. We study beam irradiation damage to molecular layers due to exposure to low-energy electrons, with implications for technological processes such as electron-beam lithography. We study photoemission and secondary electron emission from the molecular layers and highlight the critical role of unoccupied electronic band structure above the vacuum level in these processes. Finally, we present the design of, as well as the first scientific measurements in, a cryogenic sample chamber for LEEM that enables novel experiments addressing questions in surface science and condensed matter physics. Show less
Cognitive processes play an important role in human mate choice. However, far less is known about this topic in non-human animals. In this thesis, I take a comparative approach to sexually... Show moreCognitive processes play an important role in human mate choice. However, far less is known about this topic in non-human animals. In this thesis, I take a comparative approach to sexually selective cognition by studying humans (Homo sapiens) and Bornean orang-utans (Pongo pygmaeus). I start by reviewing the literature on sexually selective cognition. Hereafter, I show that visual, but not auditory or olfactory attractiveness, plays a major role in initial human mate choice. Furthermore, I show that attractiveness has a profound influence on visual attention in humans, and that attentional biases towards attractive conspecifics may be associated with mate choice. I explore the same topic in Bornean orang-utans by presenting them with stimuli of fully developed males or males experiencing arrested development. The results of these studies suggest that orang-utans preferentially attend to fully developed males, but only in the eye-tracking task and not in touchscreen tasks. The last chapter explores vocalisations, and suggests that orang-utan mate preferences might reflect in female vocal behaviour. Altogether, the results of this thesis suggest that humans and orang-utans show cognitive biases towards mate-relevant traits. However, better understanding of the link between such biases and actual mate choice remains of pivotal importance. Show less