Research master thesis | Psychology (research) (MSc)
open access
Bullying victimization is a major public health concern, because victims often experience long-term negative mental health outcomes. Longitudinal brain structure research in children is needed to...Show moreBullying victimization is a major public health concern, because victims often experience long-term negative mental health outcomes. Longitudinal brain structure research in children is needed to understand the possible mechanisms underlying the relation between bullying victimization and negative mental health outcomes. Previous research has shown that the fusiform gyrus, amygdala and vmPFC are impaired in victims. Therefore, this thesis examined the relation between victimization and fusiform gyrus, amygdala and vmPFC volume over time. We hypothesized that victims of bullying, compared to children uninvolved in bullying, would have a larger fusiform gyrus volume and a steeper volume increase. Furthermore, we hypothesized that victims of bullying, compared to children uninvolved in bullying, would have a smaller amygdala and vmPFC volume and a steeper volume decrease. The sample consisted of 156 children (62% female), aged between 7 and 9 years old at baseline, from the Leiden Consortium on Individual Development. At the beginning of the study, the Revised Olweus Bully/Victim Questionnaire was administered to measure bullying victimization and high-resolution structural MRI scans were taken. This was done again two years later. Children were classified as victims if they had been bullied regularly in the past two months. We did not find an effect of victimization on fusiform gyrus, amygdala and vmPFC volume. Future research examining the influence of victimization on both structural and functional brain development is needed to provide further insights, which can help inform the design of interventions to reduce the negative consequences of bullying victimization. The current findings emphasize the importance of protective factors that make a victim’s brain development resilient against victimization. This indicates a need for interventions targeting the development of social-emotional skills or the increase of family support.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Adolescence is characterized by the onset of puberty. Puberty, in turn is shown to be a driver of brain development and has been related to the onset and increase of internalizing symptoms. However...Show moreAdolescence is characterized by the onset of puberty. Puberty, in turn is shown to be a driver of brain development and has been related to the onset and increase of internalizing symptoms. However, the relationship between puberty, brain development, and internalizing symptoms has not been studied using multiple pubertal measures in both sexes. Here we examine the mediating role of brain development on the relationship between puberty and internalizing symptoms. Pubertal status, timing, age at menarche, and internalizing symptoms were assessed based on self-reports in 160 adolescents between 10 and 25 using a three-wave accelerated longitudinal design. Structural MRI scans were only obtained in the first wave. Subsequently, the relations between the pubertal measures (status, timing, age at menarche) and internalizing symptoms were tested as well as their relations with grey matter thickness and volume in frontal, cingulate, and subcortical areas. Only age at menarche as a timing variable had a significant effect on internalizing symptoms at T1 in girls (ß = -.36, p = .002, 95% CI [-.68, -.17]). Mediation models revealed no significant mediation of grey matter thickness and volume in our ROIs. Other effects did not reach significance or became non-significant after Bonferroni corrections. These findings indicate that menstruating before one’s peers is a risk factor for developing internalizing symptoms. This highlights the importance of supporting early menstruating girls to possibly prevent them from developing internalizing symptoms. Replication studies are needed to assess the accuracy of our results.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Building on evidence that minority representation increases minorities’ political participation, in my preregistered study, I investigated whether increased racial representation within the climate...Show moreBuilding on evidence that minority representation increases minorities’ political participation, in my preregistered study, I investigated whether increased racial representation within the climate movement causes Americans of color (N = 226) to evaluate the climate movement more positively and to encourage them to partake in climate activism. I tested this by using a 2 x 2 between-subjects design in which representation was manipulated both descriptively (i.e., the presence of people of color) and substantively (i.e., a focus on issues specifically affecting people of color) in a short video about climate activism. The results showed that descriptive representation had a positive, significant effect on evaluation of the movement, but no effects were found for substantive representation nor on climate action behavior. These findings enrich the scientific literature and provide insights on how social movements can become more inclusive, potentially increasing their effectiveness.Show less
Research master thesis | Psychology (research) (MSc)
under embargo until 2026-03-29
2026-03-29T00:00:00Z
Relevance: Efficacy of doctor empathy and nocebo education on treatment outcomes of people with cancer has been established across experimental and randomised-controlled trials (RCT). Objective: i)...Show moreRelevance: Efficacy of doctor empathy and nocebo education on treatment outcomes of people with cancer has been established across experimental and randomised-controlled trials (RCT). Objective: i) to test whether distinct effects of clinician empathy and nocebo information can also improve psychological and side effect outcomes of clinical advanced breast cancer patients undergoing chemotherapy and ii) to explore whether potential positive effects are persistent over treatment time. Methods: In this 2x2 proof-of-principle study, before treatment start, a total of 23 Dutch, chemonaïve, female breast cancer patients undergoing chemotherapy were randomised (1:1:1:1) to short information videos on chemotherapy side effects. The four videos varied on levels of empathy (+ / -) and nocebo information (+ / -). During treatment, participants’ psychological (primary outcomes: anxiety, distress) and side effect outcomes were assessed by self-report questionnaires at 7-days, 21-days, and 52-days after treatment start. Results: Repeated linear mixed model analyses indicated that empathy generally did not affect the level of anxiety (p = .440) or distress (p = .056). Empathy increased overall intensity (β = 0.76, 95% CI [.07; 1.44], p = .032) and number of side effects (β = 0.78, 95% CI [.11; 1.45], p = .025). Nocebo information did not seem to influence intensity (p = .269) or number of side effects (p = .975). Only anxiety levels were indicated to increase over time (p = .008), both at 21-days (β = 0.86, 95% CI [.25; 1.47]) and 52-days (β = 1.18, 95% CI [.38; 1.98]) post-treatment start. Conclusions: In clinical settings, advanced breast cancer patients may not profit from empathy or nocebo information. Repeating the study with a larger sample is recommended to gain clarity on communication effects. The information videos may benefit training of clinical staff and treatment consultations.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Cooperation and competition are important aspects of group behavior that have been well-researched in social psychology, but the relation between these elements has not been investigated to a...Show moreCooperation and competition are important aspects of group behavior that have been well-researched in social psychology, but the relation between these elements has not been investigated to a comparable degree. While competition between groups is known to increase cooperation within groups, the precise magnitude of its influence is not clear. Theoretically-relevant moderators that could influence this relationship have been left largely unexplored, and influential methods of studying cooperation and competition have not been assessed. Therefore, in this pre-registered meta-analysis, we investigated the impact of between-group interactions, including outright between-group competition and situations where groups compare their performance to other groups, on within-group cooperation. We conducted a systematic review of the literature involving economic games that compare cooperation in the presence of an intergroup interaction to cooperation within single groups. We compiled 17 relevant studies which yielded 47 effect sizes. Our multilevel random effects model revealed a small-to-medium, positive effect of intergroup interaction on within-group cooperation (g = 0.505, N = 4187). Confirmatory moderator analyses indicated that males, compared to females, invested more in within-group cooperation during intergroup interactions than in single, isolated groups. Additionally, effects involving intergroup comparison were weaker than effects featuring intergroup competition. Exploratory moderator analyses revealed that several variations in the methods of study impact the effect on within-group cooperation (e.g. deception, decision type, and participant matching). Our findings present compelling meta-analytic evidence that intergroup competition has a reliable impact on cooperation, and raises several opportunities for future research.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Avoidance is a hallmark symptom of Post-Traumatic Stress Disorder (PTSD), yet the link between avoidance learning and PTSD severity and treatment outcome has not yet been explored. For this purpose...Show moreAvoidance is a hallmark symptom of Post-Traumatic Stress Disorder (PTSD), yet the link between avoidance learning and PTSD severity and treatment outcome has not yet been explored. For this purpose, we administered a computer-based avoidance learning task to 144 treatment-seeking PTSD patients during the baseline assessment of a randomized clinical trial. The task consisted of a photo of blue or red colored lamps (conditional stimuli, CS+) followed by aversive photos (unconditional stimulus, US), while a photo of a yellow-colored lamp was followed by a black screen (safety stimulus, CS-). The US could be avoided by pressing a button during one CS+ (CS+ avoidable) but not the other (CS+ unavoidable). Participants were asked to fill in a threat expectancy rating after the CSs, and to report their relief after omission of the US. Participants were then given exposure therapy, and their PTSD symptoms were measured throughout 52 weeks. We predicted that higher rates of unnecessary or ineffective avoidance, higher expectancy ratings after omission of the US, and higher relief scores would relate to higher PTSD severity, and lower treatment gains. Results did not confirm any hypothesis; however, elevated threat expectancies (regardless of CStype) were related to PTSD symptom severity at baseline, and expectancies following CS- were related to PTSD severity across time points. Findings suggest general impairment in action-safety learning; however, it might be more relevant in light of PTSD severity to further explore the role of general threat expectancy. Furthermore, future studies should consider utilizing physiological measures, and adapting the task to include avoidance costs.Show less
Research master thesis | Psychology (research) (MSc)
closed access
In this study we investigated the relationship between stress, prosociality, and academic achievement. With a sample of UK-based college students, we aimed to investigate whether prosociality may...Show moreIn this study we investigated the relationship between stress, prosociality, and academic achievement. With a sample of UK-based college students, we aimed to investigate whether prosociality may serve as a buffer for the assumed negative relationship between stress and academic achievement. Our findings revealed that there was a negative relationship between academic stress and academic achievement. Furthermore, people tended to be more prosocial when they were stressed. However, this increased prosociality was not related to academic achievement and did not buffer people’s academic achievement from the negative effects of stress. The findings highlight the complex dynamic between stress, prosociality, and academic achievement. Understanding the interplay between these three variables has significant value for the innovation of interventions and preventive measures to enhance the overall well-being in students.Show less
Research master thesis | Literary Studies (research) (MA)
open access
This study examines de Digitale Stad, or the Digital City, a pioneering virtual community in the Netherlands (1994-2001), as a metaphorical urban space. Drawing from urban theory, play theory and...Show moreThis study examines de Digitale Stad, or the Digital City, a pioneering virtual community in the Netherlands (1994-2001), as a metaphorical urban space. Drawing from urban theory, play theory and media theory, this thesis analyzes how users navigated and positioned themselves in the virtual realm. By focusing on DDS and the early Web, it sheds light on the Digital City's significance as an experimental space reflecting and influencing the evolving Dutch internet landscape.Show less
Research master thesis | Literary Studies (research) (MA)
open access
This study examines de Digitale Stad, or the Digital City, a pioneering virtual community in the Netherlands (1994-2001), as a metaphorical urban space. Drawing from urban theory, play theory and...Show moreThis study examines de Digitale Stad, or the Digital City, a pioneering virtual community in the Netherlands (1994-2001), as a metaphorical urban space. Drawing from urban theory, play theory and media theory, this thesis analyzes how users navigated and positioned themselves in the virtual realm. By focusing on DDS and the early Web, it sheds light on the Digital City's significance as an experimental space reflecting and influencing the evolving Dutch internet landscape.Show less
Research master thesis | Political Science and Public Administration (research) (MSc)
closed access
The thesis examines European Union (EU) policies to address the gender pay gap (GPG) from 2006-2020. A detailed analysis of legislative and policy documents reveals the EU's active role in...Show moreThe thesis examines European Union (EU) policies to address the gender pay gap (GPG) from 2006-2020. A detailed analysis of legislative and policy documents reveals the EU's active role in promoting equal pay. The policies mainly reflect Human Capital Theory, Discrimination Theory, and Occupational Segregation Theory. The proposed actions aim to maximise women's human capital, address gender discrimination and overcome occupational segregation. However, the study identifies limitations in the conceptual frameworks, universalist approach, and lack of continuous monitoring. The research suggests the need for more specific policies, considering the diversity of women's needs, as well as dynamic monitoring mechanisms to adapt to the changing dynamics of the GPG. The thesis also challenges the limited definition of gender equality and suggests exploring additional factors to understand GPG comprehensively. In conclusion, while acknowledging the EU's commitment, the analysis reveals the need to evolve beyond traditional theories to address GPG more effectively.Show less
Research master thesis | Psychology (research) (MSc)
under embargo until 2026-02-27
2026-02-27T00:00:00Z
Food waste is a big problem in the Netherlands. In an effort to find a solution to this problem, the present study examines the influence of expiration date labels on people’s intention to waste...Show moreFood waste is a big problem in the Netherlands. In an effort to find a solution to this problem, the present study examines the influence of expiration date labels on people’s intention to waste food. The current phrase “ten minste houdbaar tot” [“at least preservable until”] can be seen as definitive and thought to refer to food safety whereas it refers to food quality, thus this study proposes an alternative phrase “beste kwaliteit voor, vaak goed na” [“best quality before, often good after”]. The aim of this alternative phrase was to make clear that the expiration date refers to food quality and that the food could still be safe to consume after this date had passed. Participants were presented with dairy and pantry products that had an expiration date that had passed by five days. This expiration date was shown with the current phrasing or the alternative phrasing. Results showed that the alternative phrase led to a lower intention to waste dairy compared to the current phrase. Whereas for pantry products, there was no difference in intention to waste food between the two phrases. Moreover, results showed that the intention to waste dairy was mediated by perceived risk. Meaning that dairy products that were presented with the alternative phrase were perceived as less risky to consume, which in turn was associated with a lower intention to let the product go to waste when the expiration had passed. Thus, changing the phrasing of the expiration date label could help in reducing food waste in the Netherlands.Show less
Research master thesis | Archaeology (research) (MA/MSc)
open access
In this study, five archaeological sites across the Netherlands from early medieval to early modern time periods were sampled to reconstruct past diet of the individuals found therein. The sites...Show moreIn this study, five archaeological sites across the Netherlands from early medieval to early modern time periods were sampled to reconstruct past diet of the individuals found therein. The sites chosen for the study were Alkmaar, Arnhem, Eindhoven, Klaaskinderkerke and Zwolle. The focus of the diet reconstruction was to analyze the childhood and adolescent diet using stable isotope analysis of carbon (δ13C) and nitrogen isotopes (δ15N). Through the use of tissues which are underutilized in archaeological diet reconstruction, dental enamel (en) and dentine (co) in conjunction, derived from second molars, it was possible to obtain isotopic ratios representative of childhood diet (enamel) and adolescent diet (dentine collagen). The results obtained were then used to analyze trends between the sites, between assigned sex and statistical relationships which served to provide grounds for further improvement of the methodology. Sampling and analysis of enamel was 100% successful, while sampling and analysis of collagen was 89% successful. The respective 76 and 68 samples were analyzed using a mass spectrometer and returned with reliable values. Results of intersite comparison aligned the, obtained results with past published literature regarding historical trends found in across the analyzed time periods, including increased consumption of marine fish in younger and more urban sites. Comparison of male and female assigned individuals has shown significant overlap between their values, suggesting that male and female individuals from the sites analyzed shared very similar diets during their childhood and adolescence. The investigation of isotope spacing of carbon values (Δen-co) allowed for determining that the diets of individuals analyzed was in large portion plant based, with significant inclusion of omnivore and marine foods as determined by isotopic ratios of carbon-13 and nitrogen-15. Analysis of statistical relationships between δ13Cen, δ13Cco and Δen-co has found a lack of correlation between δ13Cen δ13Cco, a positive correlation between Δen-co and δ13Cen and a negative correlation between Δen-co and δ13Cco. Follow-up studies should continue to investigate the recorded isotopic ratios in dental tissues, utilizing first and third molars as sources of further data capable of reconstructing sub-adult diet, as well as analyze local fauna to improve the accuracy of dietary reconstruction. The use of first and third molar isotopic ratios would also prove invaluable for investigating the statistical relationship between the tissues, due to the age of dental development and its relationship to diet reconstruction.Show less
Research master thesis | Archaeology (research) (MA/MSc)
open access
It is currently believed that there was no hominin presence on the British Isles during the Eemian interglacial stage, which lasted from 130 kya to 115 kya. However it is unclear what the reason...Show moreIt is currently believed that there was no hominin presence on the British Isles during the Eemian interglacial stage, which lasted from 130 kya to 115 kya. However it is unclear what the reason for this apparent absence is. This is especially the case considering that during the Eemian, temperatures in north-west Europe are known to have been several degrees warmer than even today, making it a potent habitat for early hominins. Several theories have existed in order to explain this, which include a complete absence in north-west Europe due to constraints in mental fortitude and an ecology that would have been unsuited for hominins to survive, as well as an early disappearance of the land bridge that connected France to Great Britain during the glacial periods. This was based on the fact that hominin sites that date back to the Eemian are exceedingly rare in north-west Europe, with the first examples only having been discovered relatively recently. This thesis aims to further explore these possibilities by making an ecological reconstruction of the site of Waziers, which is located in northern France and dates back to the Eemian. It does this based on carpological and palynological material that was found at the site. In addition to this a correlation of pollen records was made using several other Eemian type sites located in both France and Great Britain. This data is then combined with pre existing literature of other Eemian sites in north-west Europe with signs of hominin activity, in order to correlate these sites together so that Waziers can be placed in a wider chronological and climatological framework. In addition to this several other biological factors that were encountered at Waziers, are compared to the climatological conditions that were prevalent in the wider region as well. In doing so it was found the hominin activity that was detected at Waziers took place very early in the Eemian, when the stage had just transitioned from the Saalian glacial stage. In addition to this it could also be concluded that this early period was much warmer than originally anticipated. This could be seen in the presence of such indicator taxa as Lemna cf. minor, Hedera helix, and Salvinia natans, which could all be found within the vegetational record of the site. Because of these factors it is concluded that while there was already a hominin presence very early in the Eemian interglacial, which indicates that climatological conditions were at least adequate to sustain a hominin presence. It also shows that these hominins did not lack the mental fortitude to exist in these conditions, as was suggested by earlier theories. Despite this it is likely that, due to the high temperatures melting the land based ice locked in the glaciers during the Saalian, the land bridge that had existed between France and Britain during the glacial stage had already disappeared, inhibiting further hominin dispersal to the British Isles.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Language control in bilingual speakers involves effectively switching between languages, inhibiting the non-intended language, and continuously monitoring speech errors. It has been a matter of...Show moreLanguage control in bilingual speakers involves effectively switching between languages, inhibiting the non-intended language, and continuously monitoring speech errors. It has been a matter of controversy concerning whether language control operates in a comparable manner to cognitive control processes in non-linguistic domains (domain-general) or if it is exclusive to language processing (domain-specific). Midfrontal theta oscillations have been considered as an index for increased cognitive control, so examining whether a similar midfrontal theta effect is likewise evident in bilingual language will bring new insights to the ongoing debate. This study aimed to explore midfrontal theta oscillations in bilingual control with a specific focus on three fundamental control processes: language switching, inhibitory control, and speech monitoring. We reanalysed the EEG data obtained from two previous language switching studies where Dutch-English bilinguals named pictures based on colour cues. Theta power increase was observed during language switching, specifically in switch trials compared to repeat trials, and this effect was observed in the midfrontal region. Similarly, enhanced midfrontal theta power was observed during error monitoring, specifically when participants failed to select the intended language at a switch, compared to correct responses. However, no midfrontal theta effect was found during inhibitory control, reflected by a missing modulation in switch trials following a short run (i.e., a short sequence of same-language repeat trials) compared to a long run (i.e., a long sequence of same-language repeat trials). These findings largely support the involvement of domain-general cognitive control mechanisms in language control, particularly in language switching and speech monitoring, whereas inhibitory control remains unclear.Show less
Research master thesis | Archaeology (research) (MA/MSc)
open access
Diet has been one of the main drivers in the origin, evolution, and behaviour of our ancestors. Key moments in our evolutionary trajectory have been linked to changes in diet. These evolutionary...Show moreDiet has been one of the main drivers in the origin, evolution, and behaviour of our ancestors. Key moments in our evolutionary trajectory have been linked to changes in diet. These evolutionary developments include an increase in brain size, changes in habitat choice, adaptations in body size, and changes in life history. However, the Pleistocene archaeological record is highly fragmentary. To complement this lack of data, archaeology and ethnography have been combined for over decades. The predominant part of studies investigating early Homo subsistence behaviours and nutrition have focused on extant foraging populations from the African savannas to develop substantial models of human behavioural evolution. Though, studies focusing on hunter-gatherer nutrition have significantly undervalued the variability that is present within foraging diets. Furthermore, the rainforest-type environment is largely rejected its crucial role in the evolution of our lineage. The predominant part of studies have based their analyses on large-scale dietary indexes. Some authors have assumed that taken on aggregate, the average hunter-gatherer dietary profile can be recruited as a universal, ancestral diet. This led to the formation of the so-called Paleodiet movement, that attempts to help solve and understand public health issues known as the diseases of civilization such as obesity, diabetes, and other non-communicable diseases. However, it remains unclear what a uniform, ancestral Paleodiet should look like, or whether such a concept is feasible. Here, we show that hunter-gatherer nutrition is highly variable in nature, and that no uniformly applicable Paleodiet exists. By conducting a high-resolution macronutrient analysis on 30 wild edible plant taxa used by the Baka forager-horticulturalists from Southeastern Cameroon, we have shown that the nutritional qualities of wild edible plants are greatly affected by the effects of habitat and plant age, on a within- and between species level. Furthermore, we found that previously established aggregate hunter-gatherer nutritional profiles greatly differ from the reconstructed dietary- and macronutrient profiles established for the Baka. As Baka rainforest nutrition could be reverse-engineered, we illustrate that the Congo Basin rainforest-type environment provides enough macronutrients for hominins to sustain themselves without the aid of agriculture, and that the rainforest-type environment has been a crucial environment for the evolution of our lineage. Carbohydrates from starchy tubers are proposed to play a key role in Baka nutrition. Such underground storage organs are argued to have been important to early hominin nutrition within African rainforests. Public health studies may benefit by shifting their focus towards other components of Western lifestyle as more important contributors to diseases of civilization such as physical activity, stress, time spent outdoor, and overconsumption. We anticipate that future studies on extant foraging diet may greatly benefit from supplementing their use of large-scale hunter-gatherer nutritional indexes with high-resolution chemical nutritional data, as well as data 148 on weight of food brought back to camp, and estimated consumption patterns, to broaden our understanding on Pleistocene subsistence behaviour. We stimulate other research to partake in multi-disciplinary discourse for more increasingly diverse and inclusive narratives on human nutrition, Pleistocene subsistence behaviours, and human evolution. Lastly, to fully understand the influences of hominin dietary practices on the trajectory of our own evolution, it is imperative to acknowledge the plurality of both extant- and extinct hunter-gatherer lifeways, and to project a similar range of variability onto Pleistocene behaviours across different habitats.Show less
In 1895, the Dutch Social Democratic Workers’ Party (SDAP) convened for its first party conference. Two years later, the first SDAP members were elected to Parliament. Between these years and the...Show moreIn 1895, the Dutch Social Democratic Workers’ Party (SDAP) convened for its first party conference. Two years later, the first SDAP members were elected to Parliament. Between these years and the Second World War, the SDAP transitioned from a party with revolutionary aspirations to a fully normalized parliamentary entity. This thesis studies the SDAP’s assembly culture (vergadercultuur) in both the House of Representatives and their own party conferences. The first part of the thesis utilizes a combination of traditional and innovative digital methodologies to demonstrate that the normalisation of the position of the SDAP in the House of Representatives peaked in the mid-1920s. The second part of the thesis explores the development of the internal assembly culture of the SDAP, focusing on the role of the chairperson, procedures, time management, and usage of ‘persoonlijke feiten’, a phenomenon originating from Parliament. This section shows that while the internal assembly culture of the SDAP matured in many respects, this process was non-linear in many other respects, rendering the metaphor of maturation insufficient.Show less
