Research master thesis | Psychology (research) (MSc)
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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)
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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)
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 | Psychology (research) (MSc)
closed access
Poverty in the UK has increased, particularly after the Covid-19 pandemic. To prevent people from falling into a poverty trap, it is important to understand how financial scarcity affects financial...Show morePoverty in the UK has increased, particularly after the Covid-19 pandemic. To prevent people from falling into a poverty trap, it is important to understand how financial scarcity affects financial decisions involving risks. This topic lacks consensus in the literature with some authors arguing for a tendency towards more risk-taking, while others arguing for more risk aversion. This study posits that the risk tendency is influenced by frames of gains and losses. More specifically, financial scarcity leads to more risky choices in the domain of losses (H1), whereas it leads to less risky choices in the domain of gains (H2). People in financial scarcity tend to experience negative affect that impacts their cognitive systems, leading to more reliance on System 1 thinking, which exacerbates biases, such as the reflection effect. To test the hypotheses an online survey was conducted and 200 participants from the UK were recruited via Prolific Academic. The participants were divided into two groups for the manipulation of financial scarcity using the household task. Half of the participants were in the debts condition (financial scarcity), whereas the other half were not (control). Subsequently, all participants were presented with six risky choices, where they had to choose one of two options (one risky, the other conservative) framed in both gains and losses and three combinations of probabilities. Results from a Generalized Mixed Model showed that the cognitive bias associated with the reflection effect was found to be equally present in everyone and was more pronounced for more extreme probabilities (e.g., 10%/90% and 20%/80%), but not for moderate probabilities (e.g., 40%/60%). Thus, the expected interaction between debts and frames was not confirmed. It is suggested that future studies use an intuitive decision-making manipulation with more extreme probabilities (e.g., 1%/99%), consider a field risk manipulation, an incentivized lottery and the same expected value within and between probabilities at the lottery.Show less
Research master thesis | Psychology (research) (MSc)
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Within negotiations individuals differ in their motivation to reach certain outcomes over others (outcome orientation). These differences may exaggerate as asymmetrical power dynamics impose...Show moreWithin negotiations individuals differ in their motivation to reach certain outcomes over others (outcome orientation). These differences may exaggerate as asymmetrical power dynamics impose disadvantageous conditions for some individuals within a group. As such restrictions may limit an individual’s ability to realise its interest in certain outcomes, individuals may evoke compensatory mechanisms to alleviate these disadvantages. Building on previous studies (Van Tol & Steinel, 2019), we propose that creative cognitions (e.g., flexibility or originality) may qualify as such potential compensatory mechanism. Consequently, we predict that the effect of individual outcome orientation in relation to an asymmetrical dispersion of power within groups may motivate compensatory engagements in creative behaviours that aim to alleviate the effects of disadvantageous situational constraints. To this end, 150 participants took part in a three-person fictious face-to-face online study. Participants were randomly assigned to either a powerful, powerless, or equal power condition, whilst further differentiations ensured individualistic and collectivistic outcome orientations. Upon reading the instructions, participants completed both a flexibility and an originality task. Results of a 2 (social motive: pro-social vs. pro-self) x 3 (relative power: powerless vs. equal power vs. powerful) ANOVA, as well as a 2 (social motive: pro-social vs. pro-self) x 3 (relative power: powerless vs. equal power vs. powerful) ANCOVA (with individual knowledge about cooking as covariate) revealed non-significant interaction effects for both flexible (ANOVA) and original (ANCOVA) compensation. Across the possible combinations of powerless and powerful, and pro-social and pro-self, participants did not differ in their creativity scores, disconfirming our hypotheses. As these null findings stand in direct contradiction to previous literature, the need for further investigation of creative cognitions in negotiations is highlighted.Show less
Research master thesis | Psychology (research) (MSc)
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Previous studies have highlighted the role of perspective giving in improving intergroup attitudes, particularly among disadvantaged groups. Building on this research, in the current study I...Show morePrevious studies have highlighted the role of perspective giving in improving intergroup attitudes, particularly among disadvantaged groups. Building on this research, in the current study I investigated how the content of perspective giving, focused on issues of inequality or harmony between groups, influences disadvantaged group members’ motivations for collective actions towards social change. I specifically examined this within the context of Cyprus focusing on the Turkish-speaking Cypriot minority (N = 161) in relation to the Greek-speaking Cypriot majority, using a vignette experimental approach. As hypothesized, I found that participants who focused on inequalities with the advantaged outgroup reported greater support for social change, collective action intentions, and change motivation compared to those who focused on commonalities with the outgroup. However, the expected interaction with perspective giving was not found, as it did not make a difference whether the participants gave their perspective to a member of the advantaged outgroup or did not. These findings contribute to our understanding of the complexities of intergroup dynamics and extend on the possible effects of perspective giving on collective action intentions.Show less
Research master thesis | Psychology (research) (MSc)
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While the traditional bystander effect literature suggested that the presence of bystanders leads to less help provided to the victims, recent studies that focused on dangerous incidents provided...Show moreWhile the traditional bystander effect literature suggested that the presence of bystanders leads to less help provided to the victims, recent studies that focused on dangerous incidents provided evidence for decreased or even reversed bystander effect in the presence of bystanders. Although previous research proposed that the heightened arousal experienced by bystanders during dangerous incidents with in-group victims leads to increased assistance, empirical evidence supporting this claim remains limited and difficult to be studied with self-report measurements. This study addresses these limitations by employing the biopsychological model of challenge and threat (BPS-CT) to examine empirically the physiological reactions of bystanders. Participants were exposed to vignettes describing dangerous and non-dangerous incidents involving in-group and out-group victims, while their cardiovascular activity and blood pressure were measured. The presence of bystanders was found to have a marginal impact on reducing threat among bystanders, irrespective of the incident's severity. Moreover, in dangerous incidents, the presence of other bystanders and a shared in-group identity with the victim heightened participants' sense of challenge. The findings align with previous meta-analytic evidence, highlighting that bystanders are more likely to intervene in dangerous situations. The results are discussed and possible implications are proposed for designing intervention programs aimed at increasing bystander intervention rates.Show less
Conflict resolution is an inherent aspect of human interactions, representing an essential skill for achieving desirable outcomes. Moreover, recognizing individual differences during conflict may...Show moreConflict resolution is an inherent aspect of human interactions, representing an essential skill for achieving desirable outcomes. Moreover, recognizing individual differences during conflict may help understand the origins of different opinions and develop targeted strategies to solve disagreements. This study investigates whether gender and age differences influence attack investment during a conflict task in which both sides compete for different reasons. Based on research showing that women display less preference for competition, I predicted that women invest less in attack than men. Similarly, considering studies on the risk-averse behavior of older generations, I expected older individuals to invest fewer resources in attack than younger people. Three hundred one participants performed an online computer-based decision-making game following the outline of the attacker-defender contest. Participants were randomly assigned to the attacker or defender role. Depending on the role, the tasks involved deciding how to use monetary units (MU) to attack the opponent or protect one’s endowment. Attack investment was defined as the amount of MU assigned to overpower the opponent by obtaining their resources. The results contradicted the predictions, as age and gender were not significant predictors of attack investment. Therefore, this study challenges potential stereotypes claiming aggressive behavior to be more prevalent for a particular age group or gender. I discuss factors such as revising the research design and considering other individual differences that may impact the results’ significance. Altogether, recognizing and leveraging people’s unique characteristics may benefit interactions by encouraging the work toward achieving beneficial results for all parties involved.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Negative social reactions to women’s sexual assault disclosure, including disbelief, victim-blaming, and negative character judgments have detrimental consequences for survivors’ mental and...Show moreNegative social reactions to women’s sexual assault disclosure, including disbelief, victim-blaming, and negative character judgments have detrimental consequences for survivors’ mental and physical health and willingness to report the assault. Negative social reactions to female sexual assault disclosure are more often shown by men than women. This effect may be stronger, the more men identify with their gender. Negative reactions to female sexual assault disclosure among men may correspond to possible consequences of two types of social identity threat that depend on gender identification levels. High-identified men may experience threat to the value of their group (value threat), and low-identified men may experience threat of being seen primarily in terms of their male group identity (categorization threat). In the present research, we investigated belief, fault attribution, trait ratings, perceived male heterogeneity, and perceived male stigma in response to women’s disclosure of being sexually assaulted, mugged, or in an accident with men among a mixed gender (Study 1; N = 139) and a male sample (Study 2; N = 79). Study 2 additionally assessed cardiovascular threat. Results indicated that men, compared to women, expressed less belief, higher fault attribution, more negative trait ratings, and more perceived male heterogeneity and male stigma. High-identified, compared to low-identified men, displayed more negative reactions, perceived more stigma against men, and perceived less male heterogeneity. This pattern was mostly reversed for women. Male gender identification was more strongly associated with negative trait judgments of women disclosing sexual assault compared to other experiences, especially regarding morality. Men exhibited higher cardiovascular threat levels when discussing women’s disclosure of sexual assault than of an accident. Contrary to our predictions, we did not find a mediation of social reactions through cardiovascular measures that was moderated by gender identification components. Across studies, men’s reactions were mostly consistent with social identity threat responses: High-identified men’s negative reactions and perceived male stigma indicated value threat, while low-identified men’s emphasis on male heterogeneity indicated categorization threat. Our results emphasize the value of a social identity threat perspective on social reactions to sexual assault disclosure and highlight potential for future investigations with cardiovascular threat measures.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Given the practical importance of interpersonal trust in negotiations, scholars have increasingly given attention to the mechanism underlying the effect of trust and possible strategies, such as...Show moreGiven the practical importance of interpersonal trust in negotiations, scholars have increasingly given attention to the mechanism underlying the effect of trust and possible strategies, such as mediation, to handle low trust negotiations. However, research with direct mediator interventions in experimental settings has been rare. We sought to validate previous survey research on the effects of trust and a third-party mediator on negotiation outcomes, negotiator mindset, and perceptions of the negotiation. In our study we looked at the effects of a low trust or a high trust condition on dyadic level, as well as looking at the effect of the presence or absence of a mediator on how dyads negotiated. 38 participants, primarily female students from Leiden University, negotiated in a role-play scenario in a dispute as either a bar owner or a customer. Primary analyses showed no effects for trust on negotiation outcomes, mindset, or satisfaction. Due to severe limitations mediation was not analyzed. Exploratory findings showed that trust increased cooperative efforts and improved relationships, and that secondary agreements, agreements not on prices, were of importance in the negotiations. This study nuances the previously found effects of trust on negotiations and asks for more understanding of the underlying mechanisms and effects of trust.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Saving for retirement is a difficult task and individuals need to overcome many hurdles to succeed in it. When governments and companies try to help individuals, they will need to engage in choice...Show moreSaving for retirement is a difficult task and individuals need to overcome many hurdles to succeed in it. When governments and companies try to help individuals, they will need to engage in choice architecture, which means that they will exert some influence on the individuals’ decisions. Therefore, they might be held responsible for the outcomes of the individuals’ savings decisions. Evidence from two online experiments on Prolific (N = 1142) indicates that choice architecture which does not reach the desired outcome can result in a loss of trustworthiness. Further, this loss of trustworthiness depended on the exact choice architecture used. When the choice architecture did not reach the desired outcome, an individual who was presented with a suggestion perceived the trustworthiness of the CA as lower than an individual who was presented a simple free choice. Interestingly, using defaults seems to have no adverse impacts on perceived trustworthiness when the desired outcome was not reached. Finally, we discuss implications for policy and research.Show less
Research master thesis | Psychology (research) (MSc)
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This thesis examined factors that influence citizens’ food waste separation intentions through an extended norm activation model (NAM). Extensions comprised the incorporation of anticipated guilt,...Show moreThis thesis examined factors that influence citizens’ food waste separation intentions through an extended norm activation model (NAM). Extensions comprised the incorporation of anticipated guilt, anticipated disgust, and biodigester information in the model. Citizens of the municipality of Leiden, the Netherlands (N = 168) participated in an experimental survey study. One group of participants completed the survey while keeping their current waste separation options for food waste in mind, other participants received information about small-scale biodigesters and imagined a small-scale biodigester in their neighborhood. Results confirmed that the original NAM is a suitable model for explaining food waste separation intentions. In addition to previous studies, results supported our hypothesis that citizens’ outcome efficacy is positively associated with personal norms. Findings concerning extensions of the NAM were not in line with expectations. Anticipated guilt and anticipated disgust did not mediate the positive relationship between personal norms and behavioral intentions. Furthermore, outcome efficacy was not higher in participants that imagined a small-scale biodigester in their neighborhood in comparison to participants that did not. Implications regarding these findings are discussed.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Previous research indicates that the way how video evidence is presented can affect how much intent viewers ascribe suspects. With this between-subjects online study, I investigated whether pausing...Show morePrevious research indicates that the way how video evidence is presented can affect how much intent viewers ascribe suspects. With this between-subjects online study, I investigated whether pausing video evidence leads viewers to ascribe greater premeditated intent to the suspect. Further, I assessed whether this effect may arise because viewers perceive that the suspect had more time to deliberate and/or because the pause makes the deliberation moment more readily available in memory. All participants (N = 169, Mage = 21.95) were shown video evidence of a crime. The video paused either immediately before the crime, far before the crime, or did not pause. Subsequently, they judged the intent of the suspect, and suggested a charge and sentence length that the suspect should serve in detention. Results indicated that pausing video evidence did not lead viewers to ascribe greater intent to the suspect nor to demand a more severe charge. Moreover, pausing video evidence did not lead viewers to perceive that the suspect had more time to deliberate about the crime. However, the pause made the moment of deliberation more readily available in memory. Further, participants who ascribed greater intent to the suspect also demanded longer imprisonment of the suspect. This study provided preliminary insights for policymaking on how to present evidence unbiased for factfinding in court and to ensure fairer legal processes.Show less
