Research master thesis | Psychology (research) (MSc)
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Understanding the complex interactions between neurotransmitters and large-scale brain networks is crucial for unraveling the underlying neurochemical mechanisms of cognitive processes. Although...Show moreUnderstanding the complex interactions between neurotransmitters and large-scale brain networks is crucial for unraveling the underlying neurochemical mechanisms of cognitive processes. Although brain functions are modulated by a large number of neurotransmitters, one stands out for its key involvement in cognition: dopamine. This compound has been shown, although not consistently, to affect three of the main brain networks: the salience network (SN), the central executive network (CEN), and the default mode network (DMN). Specifically, an increase in dopamine has been often associated with an increase in intra SN-connectivity, resulting in a heightened negative coupling between the CEN and DMN. However, not only these results remain uncertain, but research in the field remains incomplete as until now, it has maintained a narrow focus. Thus, the present fMRI study aimed to expand on previous findings, by investigating the effects of dopamine on the SN, CEN and DMN during a working memory task. We recruited 30 healthy participants, all of which took part in two sessions, during which we manipulated their dopamine levels in the brain. To this end, in each session they received either a placebo or L-dopa, a precursor of dopamine known to increase the brain’s dopamine production and availability. During each session, participants underwent fMRI scanning, while performing a working memory task consisting of alternating working memory and rest blocks. Based on previous research, we hypothesized that dopamine would lead to a faster switch between the CEN and DMN when switching between working memory and rest blocks. In addition, we hypothesized that this faster switch would be driven by a higher intra SN connectivity. Results of paired permutation testing, as well as of a three-way ANOVA, revealed a lack of the expected dopamine-dependent changes. Dopamine did not significantly affect the switch between the CEN and DMN, nor it affected SN connectivity. These findings contradict previous literature, and call for further investigation of the dopaminergic modulation of these networks and their interactions.Show less
Research master thesis | Psychology (research) (MSc)
open access
Across clinical assessment tasks, a statistical model trained on the assessments of one person (a person’s model) has been shown to be more accurate than the person on which the model is based, the...Show moreAcross clinical assessment tasks, a statistical model trained on the assessments of one person (a person’s model) has been shown to be more accurate than the person on which the model is based, the Model-over-Person effect. Because the language that people use to express their state of mind is clinically meaningful, the objective of this study was to examine whether the Model-over-Person effect extends to language assessments as well as to identify conditions in which the effect occurs. The accuracy of the assessments of a person versus a person’s model was measured as their agreement with a reference standard (the mean assessment of multiple assessors) in two conditions: 1) the assessment of single words and 2) the assessment of texts. Artificial Intelligence based language assessments were employed to create the person’s model. No Model-over-Person effect occurred in the assessment of single words or all texts (N = 500 words/texts). A small Model-over-Person effect took place for all three assessors in the assessment of the longer texts (⩾ 50 words; dz = .39-.42; n = 23 texts). This effect be explained by the finding that a high amount of input data can make an assessment more prone to human error. Additionally, the relation between the accuracy and different assessment and language characteristics indicated that a person’s model could be more accurate in case of a low agreement among assessors and that the accuracy is not related to the confidence of the assessor in the assessment. The results show how computational language assessments can complement a person in accuracy and may support the use of computational language models as decision-support in clinical decision-making.Show less
Research master thesis | Psychology (research) (MSc)
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Communication involves understanding the difference between our own perspective (visual perspective, beliefs, and knowledge) and that of an addressee. Previous research found that knowledge about a...Show moreCommunication involves understanding the difference between our own perspective (visual perspective, beliefs, and knowledge) and that of an addressee. Previous research found that knowledge about a speaker’s background (e.g., stereotypes, accent, etc.) affects online language processing in listeners. However, the role and automaticity of Theory of Mind (ToM) – the ability to attribute beliefs to someone - remains unclear. Typically, we expect individuals to speak according to their beliefs and perspectives. But what if their utterances mismatch with what we expect them to know? We designed a novel perspective-taking paradigm in a virtual environment, which manipulates an agent’s belief. We then recorded electroencephalographical data from participants, while they listened to the agent making statements either matching or mismatching their false or true beliefs. Specifically, we analyzed the N400: a component, which amplitude scales with the unexpectedness of a content word. We predicted that statements mismatching an agent’s true belief (e.g., seeing a car and saying “That’s a screwdriver”) would result in larger N400 components, compared to statements matching the true beliefs. We found strong evidence for this prediction. Further, we predicted that knowledge of an agent’s unawareness that the state of affairs has changed (i.e., a false belief) is considered when interpreting their statements. We found indirect evidence for this: statements matching their false beliefs do not elicit an N400. However, statements mismatching their false beliefs (e.g., agent says something they couldn’t have known) neither are marked by the N400. Results support ToM’s role in interpreting language.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
The power spectral density (PSD) exponent value, indicative of the brain's excitation and inhibition (E/I) balance, has been associated with cognitive fluctuations over time and show disruptions in...Show moreThe power spectral density (PSD) exponent value, indicative of the brain's excitation and inhibition (E/I) balance, has been associated with cognitive fluctuations over time and show disruptions in neurological disorders. Yet, how this balance influences real-world behavioral dynamics remains less explored. In this study, we examined the relationship between E/I and real-world behavioral dynamics. We captured spontaneous real-world behavioral dynamics from 68 participants using inter- touch intervals (ITI) on the smartphones during a 45–90-minute EEG session. Following EEG recordings, we computed the power spectral density (PSD) over the data and applied the FOOOF method to extract the E/I balance. We then analyzed the relationship between this E/I balance and the real-world behavioral dynamics, as indicated by ITI’s. We show that real-world behavioral dynamics and E/I are related but show a considerable amount of inter-individual variability. On average, behaviors occurring between 0.03 and 1 second were accompanied by an increase in excitation, while behaviors (between 1 and 3 seconds) showed an increase in inhibition. Moreover, we identified three distinct participant types, each demonstrating unique patterns of interaction between E/I balance and real-world behavioral dynamics. In conclusion, our study emphasizes the value of the JID as a tool capable of capturing the relationship between real-world behavior and E/I on a detailed scale. This level of detail provides a unique perspective that increases our understanding of how cognition plays a role in complex real-world behavioral dynamics.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Objective: Childhood anxiety disorders are a widespread concern that may impede children’s development. Cognitive Behaviour Therapy (CBT) with exposure is considered an effective treatment for...Show moreObjective: Childhood anxiety disorders are a widespread concern that may impede children’s development. Cognitive Behaviour Therapy (CBT) with exposure is considered an effective treatment for childhood anxiety. After treatment, home practice helps children to develop skills that they learned during CBT. However, home practice is often challenging for children. Mobile health (mHealth) apps have the potential to facilitate home practice. We aimed to describe the development of the KiBA (Kids Beat Anxiety) app and test its usability. Method: In Study 1 (development phase), we included therapists (n = 5) and children (n = 8, aged 7- 14) to review app mock-ups during five meetings. IT-specialists incorporated the feedback multiple times. Next, two beta-tester groups tested the app and rated its usability. The first group tested the app for one hour at school (n = 14, mean age = 9.50), and the second group tested the app for one week at home (n = 8, mean age = 10.55). In Study 2 (clinical sample), children with a specific phobia (n = 8, Mage = 12.10) used the app for four weeks at home following CBT, and children and parents rated its usability. Results: Feedback led to multiple improvements (e.g., game elements, layout, colors, instructions). Usability ratings were both high in the beta-tester groups in the development phase (8.4/10 and 8.1/10) and the clinical sample (8.6/10 children and 8.1/10 parents). Children indicated they found the app easy, fun, and user-friendly. Conclusions: This study underlines the value of including end-users in the development of mHealth apps. The KiBA app (1) offers tools for children and their parents to practice exposure at home, and (2) helps therapists to monitor children’s progress.Show less
Research master thesis | Psychology (research) (MSc)
open access
Individuals with a lower socioeconomic status (SES) are at an increased risk for developing depressive symptoms. However, it has not been investigated whether this link is homogenous, or whether...Show moreIndividuals with a lower socioeconomic status (SES) are at an increased risk for developing depressive symptoms. However, it has not been investigated whether this link is homogenous, or whether specific depressive symptoms relate to SES differentially. In this thesis, I explored (1) which individual symptoms of depression are related to subjective social status (as a proxy for SES); (2) how specific indicators of SES are related to specific symptoms of depression; and (3) how the addition of stressors impacts the relations between SES indicators and depressive symptoms. I used data previously gathered from 448 students aged ≥18 at institutions of higher education in the Netherlands, as a part of the WARN-D study. Variables were assessed through a questionnaire that was administered online. I estimated three regularised partial correlation networks to explore shared variances among nine symptoms of depression, five indicators of SES, and seven stressors. The network analyses revealed that (1) subjective social status (as a proxy for SES) was negatively associated with guilt/worthlessness, depressed mood, anhedonia, trouble concentrating, and feeling tired, meaning that participants with higher scores on subjective social status had, on average, lower scores on these symptoms; (2) educational level (as one of multiple indicators of SES) was negatively associated with appetite disturbances, and the ability to get by financially was negatively associated with depressed mood, guilt/worthlessness, and appetite disturbances; (3) these associations diminished considerably or disappeared altogether when controlling for the stressor variables. Overall, all SES-depression associations were small in magnitude. The results suggest that patterns of depressive symptoms might differ between high-SES and low-SES individuals. Future research should explore the mechanisms behind these differences to guide prevention and intervention. My findings are consistent with previous research showing that symptom composite scores obscure important differences between individuals.Show less
Research master thesis | Psychology (research) (MSc)
open access
This study investigated whether suggestion and placebo effects can induce mystical experiences using the God Helmet, a placebo brain stimulation device. Seventy-nine participants wore the placebo...Show moreThis study investigated whether suggestion and placebo effects can induce mystical experiences using the God Helmet, a placebo brain stimulation device. Seventy-nine participants wore the placebo God Helmet for 45 minutes in sensory deprivation and were interviewed about their experience. A qualitative analysis showed that, although participants reported unusual experiences, these were distinct from their previous mystical experiences. Additionally, a permutation analysis revealed that participants rated the intensity of the God Helmet experience lower on average than their previous mystical experiences, suggesting that the God Helmet experiences are less intense. Nevertheless, the experiences induced by the God Helmet were reported as stronger than normal daydreaming and shared similarities with hypnagogic (falling asleep) states. In addition, a regression showed that individuals with more previous mystical experiences had more unusual experiences with the God Helmet and a higher Mysticism scale score, highlighting the importance of considering individual differences for understanding sensitivity to mystical-type experiences. Furthermore, as the God Helmet shows potential for inducing hypnagogic states within a 45-minute session, it has potential applications in sleep research and provides new avenues for investigating altered states of consciousness. However, as the God Helmet does not induce authentic mystical experiences with long-term positive effects, it is not an effective tool for investigating mystical experiences or applying them for therapeutic purposes.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Observing emotions in others’ facial expressions is an important factor guiding social interaction. Observing others’ emotions elicits physiological arousal in the observer, which is reflected in...Show moreObserving emotions in others’ facial expressions is an important factor guiding social interaction. Observing others’ emotions elicits physiological arousal in the observer, which is reflected in increased pupil diameter (i.e., pupil dilation). The current study used pupil dilation as an index of physiological arousal to explore children’s responses to emotional facial expressions. More specifically, we investigated whether maternal symptoms of depression and/or anxiety were related to offspring’s pupil responses to negative (versus positive) facial displays irrespective of the child’s symptomology. A community sample of 87 mother- (M = 42.30, SD = 5.60, range = 27-57) child (M = 10.11, SD = 1.32, range = 7.2-12.9) dyads participated in the current study. Mothers and offspring reported on their depressive and anxiety symptoms via self-report questionnaires. Children’s pupil responses to angry, fearful, sad, and happy dynamic facial displays were measured during the dynamic emotions task using eye-tracking. Results revealed that maternal depressive symptoms were not related to child pupil responses to negative (versus positive) faces. Higher levels of maternal anxiety, however, were linked to stronger child pupil responses to fearful and sad faces than to happy faces. In turn, child pupil responses to angry (versus happy) faces did not statistically differ as a function of maternal anxiety. These findings persisted after accounting for the link between child anxiety symptoms and child pupil responses. Therefore, the way typically developing children react to negative versus positive emotional faces in later childhood appears to be related to maternal levels of anxiety, but not to maternal levels of depression. This points to the importance of exploring maternal anxiety symptoms as a potential risk factor for the development of negativity biases in offspring across the general population.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Background: Obsessive-compulsive disorder (OCD) is a debilitating and pervasive disorder involving persistent preoccupations with intrusive thoughts (obsessions) and ritualized actions or behaviors...Show moreBackground: Obsessive-compulsive disorder (OCD) is a debilitating and pervasive disorder involving persistent preoccupations with intrusive thoughts (obsessions) and ritualized actions or behaviors (compulsions). Investigating the mechanisms underlying the development, maintenance, and treatment outcome can increase our understanding of the heterogeneity of the OCD population. One factor that may affect OCD symptom severity is self-efficacy, which is the belief in one’s capacity to perform necessary behaviors for goal attainment. Another potential factor is experiential avoidance, the avoidance of negatively perceived inner experiences including thoughts, emotions, memories, or physical sensations. This cross-sectional study is embedded in the 3D (Doorbreek Dwang Digitaal) study, which is a randomized controlled trial investigating the treatment effects of treatment for OCD by comparing exposure as usual and a personalized online approach to this therapy. The present study aimed to investigate the relationship between baseline levels of self-efficacy, experiential avoidance, and OCD symptom severity in patients with OCD. Methods: To this end, the baseline questionnaires of self-efficacy (the Self-Efficacy Questionnaire for OCD; SEQ-OCD) and experiential avoidance (the Avoidance and Acceptance Questionnaire; AAQ-II), and a structured interview for OCD symptom severity (Yale-Brown Obsessive Compulsive Scale; Y-BOCS) were used. A multiple linear regression model tested the relationship between baseline scores on the SEQ-OCD, AAQ-II, and Y-BOCS of 40 participants diagnosed with OCD. Consecutively, a hierarchical and a k-means clustering analysis were performed, to form clusters of participants using the SEQ-OCD, AAQ-II, and Y-BOCS baseline scores. Results: Results showed that self-efficacy had a significant negative relationship with OCD symptom severity, as higher levels of self-efficacy were associated with a lower level of OCD symptom severity. However, this relationship was not significant anymore when experiential avoidance was added to the model. Experiential avoidance was not significantly related to OCD symptom severity or self-efficacy. With hierarchical and k-means clustering, two clusters were identified that significantly differed in levels of self-efficacy, OCD symptom severity, and experiential avoidance. One cluster showed significantly higher levels of OCD symptom severity and experiential avoidance and significantly lower levels of self-efficacy. This cluster also experienced more obsessions involving contamination, religion, symmetry/ordering, and more compulsions involving cleaning and counting. Conclusion: This study indicates that there is a relationship between self-efficacy and OCD symptom severity. Moreover, we found evidence of distinct groups of OCD patients with different levels of self-efficacy, OCD symptom severity, experiential avoidance, and different OCD symptom subtypes. This may indicate a differential role of self-efficacy and experiential avoidance across the different OCD symptom subtypes. Limitations of this study included the small sample size and the overrepresentation of females and the contamination obsession subtype. Future studies using larger sample sizes and a more diverse sample are required to further establish the precise mechanism of self-efficacy and symptom subtype in the development and maintenance of OCD.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Atomoxetine is a prescription drug often used to restore executive (or cognitive) functioning in patients with attention-deficit/hyperactivity disorder and other neuropsychiatric conditions....Show moreAtomoxetine is a prescription drug often used to restore executive (or cognitive) functioning in patients with attention-deficit/hyperactivity disorder and other neuropsychiatric conditions. Moreover, this drug may potentially be ingested by healthy individuals who seek to improve their cognitive performance. However, the effect of atomoxetine on healthy brain functioning remains largely unclear. Network approaches have become useful for studying how the functional connectivity between brain regions may enhance or hinder executive functioning. Accordingly, to further examine the underlying mechanisms of action of atomoxetine, it is relevant to explore how this drug influences the functional connectivity of a large-scale brain network involved in the control of top-down processes: the executive control network (ECN). The aim of this study was thus to investigate the effect of atomoxetine (40 mg) on the functional connectivity of the ECN in healthy volunteers (n = 15). Network analyses were conducted on unpublished functional magnetic resonance (fMRI)-data collected by Chamberlain and colleagues (2009) in a double-blind, placebo-controlled, within-subjects, crossover design in which participants completed a goal-directed fMRI-task (i.e., the temporal discounting task), probing the ECN. Contrary to expectations, a paired-samples permutation test, corrected for multiple comparisons by means of a threshold free cluster enhancement, revealed that the functional connectivity of the participants’ ECN does not increase significantly after ingesting atomoxetine as compared to placebo (p > .05 corrected). Nevertheless, exploratory analyses indicated that, relative to placebo, atomoxetine significantly strengthens the functional connectivity of a frontoparietal network highly associated with cognition and language paradigms (t(14) = 7.61, p = .003). Together, these results suggest that, in healthy individuals, atomoxetine might not have enhancing effects on the processes supported by the ECN but (potentially) on those supported by a frontoparietal network. Atomoxetine might thus have beneficial effects in the cognitive performance of healthy individuals by facilitating certain processes associated with both cognition and language. Further research is however warranted to corroborate these findings in confirmatory studies and enhance the understanding of the underlying mechanisms of action of atomoxetine in healthy brain functioning.Show less
Research master thesis | Psychology (research) (MSc)
open access
Autism Spectrum Disorder (ASD) is a highly heritable disorder that is more prevalent in males than females. Genetic mechanisms of the sexual differentiation could therefore contribute to the sex...Show moreAutism Spectrum Disorder (ASD) is a highly heritable disorder that is more prevalent in males than females. Genetic mechanisms of the sexual differentiation could therefore contribute to the sex differences in ASD. An unexplored pathway lies in the potential contribution of the direct effect of the X chromosome imbalance. Due to the X chromosome’s implications in brain structure, the imbalance in X chromosomes could contribute to recently discovered sex differences in brain structure variance. As males showed larger brain structure variance, they have generally larger brain structure deviations compared to females. If increasing brain structure deviations relate to increased ASD risk, this mechanism could explain why males show higher ASD prevalence compared to females. To assess an influence of the X chromosome imbalance on sex differences in brain structure variance, we assessed the sex difference in brain structure variance in brain regions with a high and low expression of the X chromosome. We then assessed whether larger brain structure deviations related to increased ASD symptoms. This was examined in a population of typically developing individuals aged 7 to 14. The X chromosome expression did not affect sex differences in brain structure variance. Therefore, our results did not support an effect of the X chromosome imbalance on sex differences in brain structure variance. Additionally, brain deviation showed no relationship with ASD symptoms. Our results do not support a contribution of sex differences in brain structure variance to sex differences in ASD. Our findings could suggest potential influences of other downstream effects of the chromosomal imbalance and the high heterogeneity of ASD.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
