Pilleriin Sikka is a postdoctoral research fellow in the Department of Psychology at Stanford University, a postdoctoral researcher in the Department of Psychology at the University of Turku (Finland), and a senior lecturer in cognitive neuroscience in the Department of Cognitive Neuroscience and Philosophy at the University of Skövde (Sweden). She holds a PhD degree in psychology (University of Turku, Finland), MSc degree in neuroscience (University of Oxford, UK), as well as MSc and BSc degrees in psychology (University of Tallinn, Estonia). Previously, she worked in the Department of Psychiatry at the University of Oxford (UK) in the field of molecular neuroscience. Pilleriin has received several prestigious research (e.g., Postdoctoral Reseach Award from the Finnish Foundations' Post Doc Pool) and teaching (The Golden Apple Award for Excellence in Teaching) awards as well as research grants (as a PI) from international and national foundations. She has more than ten years of teaching experience (courses in neuroscience, psychology, and well-being) and supervised as well as served as a mentor to many undergraduate and graduate students in the fields of psychology and cognitive neuroscience.

Honors & Awards

  • Merited Lecturer (awarded for excellence in research-based teaching), University of Skövde, Sweden (2022)
  • First Prize for PhD dissertation, Skaraborg’s Academy, Sweden (2021)
  • PhD Dissertation Award, The Finnish Sleep Research Society, Finland (2021)
  • Postdoctoral Fellowship, The Finnish Foundations' Post Doc Pool and the Emil Aaltonen Foundation (2020)
  • The Golden Apple Award for Excellence in Teaching, University of Skövde, Sweden (2020)
  • Best Poster Award, The Finnish Sleep Research Society, Finland (2018)
  • The Golden Apple Award for Excellence in Teaching, University of Skövde, Sweden (2015)
  • The Golden Apple Award for Excellence in Teaching, University of Skövde, Sweden (2010)
  • Winner of the Main Prize at the National Contest for University Students, Estonian Research Council (2005)
  • Winner of the Main Prize at the Contest of Students’ Research Papers, Tallinn University, Estonia (2005)
  • Harald Raudsep Scholarship, Estonian-Revelia Academic Fund, Maryland, USA (2005)
  • Kristjan Jaak Scholarship, Archimedes Foundation, Estonia (2005)
  • Kristjan Jaak Scholarship, Archimedes Foundation, Estonia (2004)
  • National Scholarship, Estonian Ministry of Education and Research, Estonia (2000)

Boards, Advisory Committees, Professional Organizations

  • Member, Society for Affective Science (SAS)
  • Member, International Society for Research on Emotion (ISRE)
  • Member, Association for the Scientific Study of Consciousness (ASSC)
  • Member, European Sleep Research Society (ESRS)
  • Member, Finnish Sleep Research Society (SUS)
  • Member, International Association for the Scientific Study of Dreams (IASD)

Professional Education

  • Ph.D., University of Turku (Finland), Psychology (2020)

Stanford Advisors

Current Research and Scholarly Interests

Pilleriin's main research interests focus on emotions and emotion regulation, mental well-being, sleep and dreaming, and consciousness. More specifically, she conducts research on the nature and continuity of emotions and emotion regulation across the wake-sleep cycle and how these are related to health and well-being. She also strives to understand the psychology and neurobiology of peace of mind as an aspect of mental well-being. In her research Pilleriin uses a multidisciplinary and multilevel framework that draws on the concepts, theories, and methods from the fields of philosophy, psychology, (affective) neuroscience, and (molecular) biology, and integrates different research areas, such as emotion research, sleep and dream research, consciousness research, and well-being research.

Lab Affiliations

All Publications

  • The Perth Alexithymia Questionnaire-Short Form (PAQ-S): A 6-item measure of alexithymia. Journal of affective disorders Preece, D. A., Mehta, A., Petrova, K., Sikka, P., Bjureberg, J., Chen, W., Becerra, R., Allan, A., Robinson, K., Gross, J. J. 2023


    BACKGROUND: Alexithymia is a trait characterized by difficulties identifying feelings, difficulties describing feelings, and externally orientated thinking. It is widely regarded as an important transdiagnostic risk factor for a range of psychopathologies, including depressive and anxiety disorders. Whilst several well-validated psychometric measures of alexithymia exist, these are relatively lengthy, thus limiting their utility in time-pressured settings. In this paper, we address this gap by introducing and validating a brief 6-item version of the Perth Alexithymia Questionnaire, called the Perth Alexithymia Questionnaire-Short Form (PAQ-S).METHOD: Across two studies with adult samples (Study 1 N = 508 United States community; Study 2378 Australian college students), we examined the psychometric properties of the PAQ-S in terms of its factor structure, reliability, and concurrent/criterion validity.RESULTS: In exploratory and confirmatory factor analyses, all PAQ-S items loaded well on a single general alexithymia factor. The PAQ-S total score had high reliability, and correlated as expected with the long-form of the PAQ, as well as other established markers of alexithymia, emotion regulation, and affective disorder symptoms.LIMITATIONS: Our samples were general community or college student samples from two Western countries; future validation work in clinical samples and more diverse cultural groups is thus needed.CONCLUSIONS: The PAQ-S retains the psychometric strengths of the PAQ. As such, the PAQ-S can be used as a quick, robust measure of overall alexithymia levels. The introduction of the PAQ-S hence enables valid assessments of alexithymia in a more diverse range of settings and research designs.

    View details for DOI 10.1016/j.jad.2023.01.036

    View details for PubMedID 36642314

  • Alexithymia and emotion regulation. Journal of affective disorders Preece, D. A., Mehta, A., Petrova, K., Sikka, P., Bjureberg, J., Becerra, R., Gross, J. J. 2022


    Alexithymia is a key transdiagnostic risk factor for emotion-based psychopathologies. Conceptual models specify that this is because alexithymia impairs emotion regulation. However, the extent of these putative emotion regulation impairments remains underexplored. Our aim in this study was to begin to address this gap by examining whether people with high, average, or low levels of alexithymia differ in the types of emotion regulation strategies they typically use.General community adults from the United States (N = 501) completed a battery of alexithymia and emotion regulation measures. Participants were grouped into high, average, and low alexithymia quantiles.After controlling for demographics and current levels of distress, the high, average, and low alexithymia groups differed in their use of cognitive and behavioral emotion regulation strategies. Compared to the other groups, the high alexithymia group reported lesser use of generally adaptive regulation strategies (cognitive reappraisal, approaching problems, and seeking social support) and greater use of generally maladaptive regulation strategies (expressive suppression, behavioral withdrawal, ignoring).Our data were cross-sectional and from self-report questionnaires. Future work in other cultural groups would be beneficial.Our results support the view that alexithymia is associated with impaired emotion regulation. In particular, people with high alexithymia seem to exhibit a less adaptive profile of emotion regulation strategies. Direct targeting of these emotion regulation patterns in psychotherapy may therefore be a useful pathway for the treatment of emotional disorder symptoms in people with high alexithymia.

    View details for DOI 10.1016/j.jad.2022.12.065

    View details for PubMedID 36566943

  • The Neural Bases of Expressive Suppression: A Systematic Review of Functional Neuroimaging Studies. Neuroscience and biobehavioral reviews Sikka, P., Stenberg, J., Vorobyev, V., Gross, J. J. 2022: 104708


    Expressive suppression refers to the inhibition of emotion-expressive behavior (e.g., facial expressions of emotion). Although it is a commonly used emotion regulation strategy with well-documented consequences for well-being, little is known about its underlying mechanisms. In this systematic review, we for the first time synthesize functional neuroimaging studies on the neural bases of expressive suppression in non-clinical populations. The 12 studies included in this review contrasted the use of expressive suppression to simply watching emotional stimuli. Results showed that expressive suppression consistently increased activation of frontoparietal regions, especially the dorsolateral and ventrolateral prefrontal cortices and inferior parietal cortex, but decreased activation in temporo-occipital areas. Results regarding the involvement of the insula and amygdala were inconsistent with studies showing increased, decreased, or no changes in activation. These mixed findings underscore the importance of distinguishing expressive suppression from other forms of suppression and highlight the need to pay more attention to experimental design and neuroimaging data analysis procedures. We discuss these conceptual and methodological issues and provide suggestions for future research.

    View details for DOI 10.1016/j.neubiorev.2022.104708

    View details for PubMedID 35636561

  • Negative dream affect is associated with next-day affect level, but not with affect reactivity or affect regulation. Frontiers in behavioral neuroscience Sikka, P., Engelbrektsson, H., Zhang, J., Gross, J. J. 2022; 16: 981289


    There is increasing evidence that sleep plays an important role in affective processing. However, it is unclear whether dreaming-the subjective experiences we have during sleep-also serves an affect regulation function. Here, we investigated the within-person relationship between negative affect experienced in dreams and next-day waking affect level, affect reactivity, and affect regulation. For 5 days, 40 participants reported their dreams and rated their dream affect and post-sleep waking affect level upon morning awakening. Thereafter, they performed an affect reactivity and regulation task which involved viewing neutral and negative pictures with the instruction either to simply view the pictures or to down-regulate the affect evoked by these pictures. Multilevel regression analyses showed that the more negative affect people experienced in their dreams at night, the more negative affect and the less positive affect they reported the next morning. However, negative dream affect was associated neither with affect reactivity to the pictures nor with the ability to down-regulate negative affect in response to these pictures. In fact, Bayesian analyses favored the null hypotheses. These findings fail to provide support for the affect regulation function of dreaming and, instead, speak for affective continuity between dreaming and post-sleep wakefulness.

    View details for DOI 10.3389/fnbeh.2022.981289

    View details for PubMedID 36338877

  • The dynamics of affect across the wake-sleep cycle: From waking mind-wandering to night-time dreaming. Consciousness and cognition Sikka, P., Valli, K., Revonsuo, A., Tuominen, J. 2021; 94: 103189


    Affective experiences occur across the wake-sleep cycle-from active wakefulness to resting wakefulness (i.e., mind-wandering) to sleep (i.e., dreaming). Yet, we know little about the dynamics of affect across these states. We compared the affective ratings of waking, mind-wandering, and dream episodes. Results showed that mind-wandering was more positively valenced than dreaming, and that both mind-wandering and dreaming were more negatively valenced than active wakefulness. We also compared participants' self-ratings of affect with external ratings of affect (i.e., analysis of affect in verbal reports). With self-ratings all episodes were predominated by positive affect. However, the affective valence of reports changed from positively valenced waking reports to affectively balanced mind-wandering reports to negatively valenced dream reports. These findings show that (1) the positivity bias characteristic to waking experiences decreases across the wake-sleep continuum, and (2) conclusions regarding affective experiences depend on whether self-ratings or verbal reports describing these experiences are analysed.

    View details for DOI 10.1016/j.concog.2021.103189

    View details for PubMedID 34419707