Ionica Smeets


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Professor of Science Communication - Leiden University


The publications listed below are in reverse chronological order and separated by year of publication.


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Evers A.W.M., Colloca L., Blease C, Gaab J., Jensen K.B., Atlas L.Y., Beedie C.J., Benedetti F., Bingel U., Büchel C., Bussemaker M., Colagiuri B., Crum A.J., Finniss D.G., Geers A.L., Howick J., Klinger R., Meeuwis S.H., Meissner K., Napadow V., Petrie K.J., Rief W., Smeets I., Wager T.D., Wanigasekera V., Vase L., Kelley J.M. & Kirsch I. (2020). What Should Clinicians Tell Patients about Placebo and Nocebo Effects? Practical Considerations Based on Expert Consensus. Psychotherapy and Psychosomatics, 90(1), 49–56. doi: 10.1159/000510738

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Clinical and laboratory studies demonstrate that placebo and nocebo effects influence various symptoms and conditions after the administration of both inert and active treatments.
There is an increasing need for up–to–date recommendations on how to inform patients about placebo and nocebo effects in clinical practice and train clinicians how to disclose this information.
Based on previous clinical recommendations concerning placebo and nocebo effects, a 3–step, invitation–only Delphi study was conducted among an interdisciplinary group of internationally recognized experts. The study consisted of open– and closed–ended survey questions followed by a final expert meeting. The surveys were subdivided into 3 parts: (1) informing patients about placebo effects, (2) informing patients about nocebo effects, and (3) training clinicians how to communicate this information to the patients.
There was consensus that communicating general information about placebo and nocebo effects to patients (e.g., explaining their role in treatment) could be beneficial, but that such information needs to be adjusted to match the specific clinical context (e.g., condition and treatment). Experts also agreed that training clinicians to communicate about placebo and nocebo effects should be a regular and integrated part of medical education that makes use of multiple formats, including face–to–face and online modalities.
The current 3–step Delphi study provides consensus–based recommendations and practical considerations for disclosures about placebo and nocebo effects in clinical practice. Future research is needed on how to optimally tailor information to specific clinical conditions and patients′ needs, and on developing standardized disclosure training modules for clinicians.

Willems, S.J.W., Albers, C.J., & Smeets, I. (2020). Variability in the interpretation of probability phrases used in Dutch news articles–a risk for miscommunication. Journal of Science Communication, 19(2), A03. doi: 10.22323/2.19020203

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Verbal probability phrases are often used in science communication to express estimated risks in words instead of numbers. In this study we look at how laypeople and statisticians interpret Dutch probability phrases that are regularly used in news articles. We found that there is a large variability in interpretations, even if the phrases are given in a neutral context. Also, statisticians do not agree on the interpretation of the phrases. We conclude that science communicators should be careful in using verbal probability expressions.

Grimmon, A. S., Cramer, J., Yazilitas, D., Smeets, I., & Bruyckere, P. D. (2020). Interest in STEM among children with a low socio–economic status: further support for the STEM–CIS–instrument through the adapted Dutch STEM–LIT measuring instrument. Cogent Education, 7(1). doi: 10.1080/2331186x.2020.1745541

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When in 2014 the STEM Career Interest Survey (STEM–CIS) was developed, the researchers could check this instrument with other target audiences. Also, the question remained if the instrument was applicable for both boys and girls. This article describes the development and validation of a Dutch language version of it, called the STEM–LIT instrument, an instrument to measure the interest of children aged between ten and 12 years in Science, Technology, Engineering and Mathematics (STEM), focusing specifically on children from families with low socio–economic status (SES). The instrument has been adapted and developed in five stages and tested among Dutch primary school pupils in groups seven and eight (ages 10–11 and 11–12). The instrument was first tested in two pilot studies, after which some amendments were made. The final version of the instrument was tested with 212 pupils, with a Cronbach′s Alpha of.91, adding supporting evidence to the reliability of the original STEM–CIS instrument and showing that the test is as reliable for both girls and boys.

Hooykaas, M. J. D., Schilthuizen, M., & Smeets, I. (2020). Expanding the Role of Biodiversity in Laypeople′s Lives: The View of Communicators. Sustainability, 12(7), 2768. doi: 10.3390/su12072768

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Biodiversity is a fundamental part of sustainable development, yet it is threatened by numerous factors associated with human population growth. The current lack of broad–based support for biodiversity conservation may be explained by the widening gap between people and nature. In order to conserve biodiversity, people should be engaged in biodiversity, yet it is not yet clear what potential is present in highly urbanized environments. We conducted semi–structured interviews with twelve biodiversity communicators in the Netherlands, a highly urbanized country, and used their perceptions and experiences to explore motivations, opportunities and challenges for expanding the role of biodiversity in people′s lives in an increasingly urban world. Overall, the interviewees perceived the current role of biodiversity in laypeople′s lives to be too limited, but they were positive about the potential to expand the role. Based on communicators′ perceptions potential lies in a combination of direct exposure to biodiversity outdoors, the media, and education. Furthermore, strategically designed communication is also expected to play an essential part in opening people′s eyes for biodiversity. The results are valuable both at national and international levels, as they can motivate and aid professionals operating in urbanized contexts at reaching out to their audiences about biodiversity.

Cheplygina, V., Hermans, F., Albers, C., Bielczyk, N., & Smeets, I. (2020). Ten simple rules for getting started on Twitter as a scientist. PLOS Computational Biology, 16(2). doi: 10.1371/journal.pcbi.1007513

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Twitter is one of the most popular social media platforms, with over 320 million active users as of February 2019. Twitter users can enjoy free content delivered by other users whom they actively decide to follow. However, unlike in other areas where Twitter is used passively (e.g., to follow influential figures and/or information agencies), in science it can be used in a much more active, collaborative way: to ask for advice, to form new bonds and scientific collaborations, to announce jobs and find employees, to find new mentors and jobs. This is particularly important in the early stages of a scientific career, during which lack of collaboration or delayed access to information can have the most impact.
For these reasons, using Twitter appropriately can be more than just a social media activity; it can be a real career incubator in which researchers can develop their professional circles, launch new research projects and get helped by the community at various stages of the projects. Twitter is a tool that facilitates decentralization in science; you are able to present yourself to the community, to develop your personal brand, to set up a dialogue with people inside and outside your research field and to create or join professional environment in your field without mediators such as your direct boss.
This article is written by a group of researchers who have a strong feeling that they have personally benefited from using Twitter, both research–wise and network–wise. We (@DrVeronikaCH, @Felienne, @CaAl, @nbielczyk_neuro, @ionicasmeets) share our personal experience and advice in the form of ten simple rules, and we hope that this material will help a number of researchers who are planning to start their journey on Twitter to take their first steps and advance their careers using Twitter.


Hariman, N., de Vries, M., & Smeets, I. (2019). Topic Modeling for Exploring Cancer–Related Coverage in Journalistic Texts. In Atzmueller M., Duivesteijn W. (Eds.) Artificial Intelligence. BNAIC 2018. Communications in Computer and Information Science, vol 1021 (pp. 43–51). Springer, Cham.


Topic modeling has been used for many applications, but has not been applied to science and health communication research yet. In this paper, using topic modeling for this novel domain is explored, by investigating the coverage of cancer in news items from the New York Times since 1970 with the Latent Dirichlet Allocation (LDA) model. Content analysis of cancer in print media has been performed before, but at a much smaller scope and with manual rather than computational analysis. We collected 45.684 articles concerning cancer via the New York Times API to build the LDA model upon.
Our results show a predominance of breast cancer in news articles as compared with other types of cancer, similar to previous studies. Additionally, our topic model shows 6 distinct topics: research on cancer, lifestyle and mortality, the healthcare system, business and insurance issues regarding cancer treatment, environmental politics and American politics on cancer–related policies.
Since topic modeling is a computational technique, the model has more difficulty with understanding the meaning of the analyzed text than (most) humans. Therefore, future research will be set up to let the public contribute to analysis of a topic model.

Hooykaas, M. J., Schilthuizen, M., Aten, C., Hemelaar, E. M., Albers, C. J., & Smeets, I. (2019). Identification skills in biodiversity professionals and laypeople: A gap in species literacy. Biological Conservation, 238, 108202.

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Biodiversity is in worldwide decline and it is becoming increasingly important to expand biodiversity awareness and achieve broad–based support for conservation. We introduce the concept of species literacy, as knowledge about species can be a good starting point for engaging people in biodiversity. However, concern has been raised about a general lack of knowledge about native species. We explored species literacy via a species identification test in the Netherlands, and we investigated potential drivers of it. The dataset included 3210 general public participants, 602 primary school children aged 9/10, and 938 biodiversity professionals.
A considerable gap in species literacy was found between professionals and laypeople. Knowledge about common, native animals was particularly low in children, who on average identified only 35% of the species correctly. Mammals received relatively high identification scores as compared to birds. Laypeople′s species literacy increased with age and educational level, and was associated with positive attitudes towards nature and animals, media exposure and having a garden.
The results indicate that a considerable part of the Dutch lay public is disconnected from native biodiversity. This points to a separation between people and nature that could hinder future efforts to preserve biodiversity. Our assessment can help bridge the gap between laypeople and professionals, as it can help set up communication and education strategies about native biodiversity that fit prior knowledge.

Bossema, F.G., Burger, P., Bratton, L., Challenger, A., Adams, R.C., Sumner, P., Schat, J., Numans, M.E., & Smeets, I. (2019). Expert quotes and exaggeration in health news: a retrospective quantitative content analysis. Wellcome Open Research 4, 56. doi: 10.12688/wellcomeopenres.15147.1

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This research is an investigation into the role of expert quotes in health news, specifically whether news articles containing a quote from an independent expert are less often exaggerated than articles without such a quote.
Retrospective quantitative content analysis of journal articles, press releases, and associated news articles was performed. The investigated sample are press releases on peer–reviewed health research and the associated research articles and news stories. Our sample consisted of 462 press releases and 668 news articles from the UK (2011) and 129 press releases and 185 news articles from The Netherlands (2015). We hand–coded all journal articles, press releases and news articles for correlational claims, using a well–tested codebook. The main outcome measures are types of sources that were quoted and exaggeration of correlational claims. We used counts, 2x2 tables and odds ratios to assess the relationship between presence of quotes and exaggeration of the causal claim.
Overall, 99.1% of the UK press releases and 84.5% of the Dutch press releases contain at least one quote. For the associated news articles these percentages are: 88.6% in the UK and 69.7% in the Netherlands. Authors of the study are most often quoted and only 7.5% of UK and 7.0% of Dutch news articles contained a new quote by an expert source, i.e. one not provided by the press release. The relative odds that an article without an external expert quote contains an exaggeration of causality is 2.6.
The number of articles containing a quote from an independent expert is low, but articles that cite an external expert do contain less exaggeration.

Venhuizen, G. J., Hut, R., Albers, C., Stoof, C. R., & Smeets, I. (2019). Flooded by jargon: How the interpretation of water–related terms differs between hydrology experts and the general audience. Hydrology and Earth System Sciences Discussions, 23(1), 393–403. doi:10.5194/hess–2018–297

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Communication about water–induced hazards (such as floods, droughts or levee breaches) is important, in order to keep their impact as low as possible. However, sometimes the boundary between specialized and non–specialized language can be vague. Therefore, a close scrutiny of the use of hydrological vocabulary by both experts and laypeople is necessary.
In this study, we compare the expert and layperson definitions of 22 common terms and pictures related to water and water hazards, to see where misunderstandings might arise both in text and pictures. Our primary objective is to analyze the degree of agreement between experts and laypeople in their definition of the used terms. In this way, we hope to contribute to improving the communication between these groups in the future. Our study was based on a survey completed by 34 experts and 119 laypeople.
Especially concerning the definition of words related to water there are some profound differences between experts and laypeople: words like “river” and “river basin” turn out to have a thoroughly different interpretation between the two groups. Concerning the pictures, there is much more agreement between the groups.

Vries, M. D., Land–Zandstra, A., & Smeets, I. (2019). Citizen Scientists′ Preferences for Communication of Scientific Output: A Literature Review. Citizen Science: Theory and Practice, 42. doi:10.5334/cstp.136

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Many citizen science developers agree that participants in citizen science projects need to receive feedback on project outputs and that they should be recognized in results and publications. However, little research has thoroughly investigated the extent to which citizen scientists find communication of scientific output to be important. Citizen science studies rarely investigate this topic as their main goal. Therefore, we conducted a review on participants′ preferences for communication of data, findings, and scientific publications in papers that focus on participant motivation but which also contain relevant evidence about communication in parts of the results. We reviewed 32 peer–reviewed papers that contained relevant evidence in quantitative analyses (e.g., Likert scale–type questions) or in qualitative analyses (e.g., interviews with participants).
From this review, we conclude that participants value accessibility of their collected data, communication of project findings, and acknowledgement in publications. Taking this into account can pay off, as sharing data and findings can enhance the motivation of participants to engage in the project, thereby sustaining their participation, imparting the feeling that they spent their time well, and increasing a project′s learning impact. Some practical and ethical issues such as privacy concerns, however, need to be taken into account. This literature review is the first to provide an overview of citizen scientists′ preferences for communication of scientific output, and is a starting point for further research that should investigate the impact of different options for data sharing and communication of findings to participants.


Smeets, I. (2018). What Do People Like about Mathematics? Adults Learning Mathematics: An International Journal, 13, 7.

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In this discussion paper we look at questions that adults have about numbers. Many of their questions are not about pure mathematics, but about personal, cultural or societal issues. We discuss how to connect mathematical topics with things people are interested in, based on theoretic knowledge from the field of science communication. We focus on using narratives to make mathematics more personal, how to use games as demonstrations and different ways to present the same mathematical problem in different societal settings.

Schat, J., Bossema, F.G., Numans, M.E., Smeets, I., & Burger, J.P. (2018). Overdreven gezondheidsnieuws. Relatie tussen overdrijving in academische persberichten en in nieuwsmedia. Nederlands Tijdschrift voor Geneeskunde, 162, 5.

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Bepalen hoe vaak pers– en nieuwsberichten overdrijvingen bevatten en onderzoeken waar in het traject tussen wetenschappelijke publicatie en nieuwsbericht deze overdrijving ontstaat.
Retrospectieve kwantitatieve inhoudsanalyse.
We analyseerden persberichten over gezondheidsonderzoek die door de Nederlandse universiteiten en universitaire medische centra in 2015 waren uitgebracht (n = 129) en de aan die persberichten gerelateerde berichten in de nieuwsmedia (n = 185).
20% van de persberichten en 29% van de nieuwsberichten bevatten overdrijving van de conclusie of causale claim. Expliciet gezondheidsadvies werd indien aanwezig overdreven in 7% van de persberichten en in 10% van de nieuwsberichten. Wanneer het persbericht een overdrijving van de conclusie of causale claim bevatte, stond in 92% van de gerelateerde nieuwsberichten dezelfde overdrijving. Als de conclusie in het persbericht niet overdreven was, was 6% van de nieuwsberichten overdreven. De relatieve kans op overdreven nieuws bij een overdreven persbericht was 16,08 (95%–BI: 7,35–35,18). Bij overdreven persberichten hoorde vaker een nieuwsbericht. De relatieve kans op een nieuwsbericht bij een overdreven persbericht tegenover een niet–overdreven persbericht was 1,45 (95%–BI: 1,02–2,04).
Overdrijving in gezondheidsnieuws gaat sterk gepaard met overdrijving in het oorspronkelijke persbericht en komt voor bij meer dan 1 op de 5 artikelen. Het monitoren en zo nodig verbeteren van de nauwkeurigheid en juistheid van academische persberichten lijken een belangrijke stap om de kwaliteit van gezondheidsnieuws te verhogen.


Smeets, I. (2017). Gelijk hebben én krijgen. Vakmedianet.

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Tijdens het voorgesprek voor deze Jan de Kroes–lezing vertelde de organisatie dat veiligheidsexperts vaak mopperen dat hun leidinggevenden niet naar hen luisteren. Terwijl zij toch echt gelijk hebben, zij weten immers precies wat de risico′s zijn. Helaas blijkt het vaak lastig om anderen te overtuigen, zelfs als de feiten aan je kant staan.


Hut, R. Land–Zandstra, A.M., Smeets, I., & Stoof, C.R. (2016). Geoscience on television: a review of science communication literature in the context of geosciences. Hydrology and Earth System Sciences, 20(6), 2507–2518. doi:10.5194/hess–20–2507–2016

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Geoscience communication is becoming increasingly important as climate change increases the occurrence of natural hazards around the world. Few geoscientists are trained in effective science communication, and awareness of the formal science communication literature is also low. This can be challenging when interacting with journalists on a powerful medium like TV. To provide geoscience communicators with background knowledge on effective science communication on television, we reviewed relevant theory in the context of geosciences and discuss six major themes: scientist motivation, target audience, narratives and storytelling, jargon and information transfer, relationship between scientists and journalists, and stereotypes of scientists on TV. We illustrate each theme with a case study of geosciences on TV and discuss relevant science communication literature. We then highlight how this literature applies to the geosciences and identify knowledge gaps related to science communication in the geosciences. As TV offers a unique opportunity to reach many viewers, we hope this review can not only positively contribute to effective geoscience communication but also to the wider geoscience debate in society.


Bosma, W., & Smeets, I. (2013). Finding simultaneous Diophantine approximations with prescribed quality. The Open Book Series, 1(1), 167–185. doi:10.2140/obs.2013.1.167

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We give an algorithm that finds a sequence of approximations with Dirichlet coefficients bounded by a constant only depending on the dimension. The algorithm uses LLL lattice basis reduction. We present a version of the algorithm that runs in polynomial time of the input.


Kraaikamp, C., & Smeets, I. (2011). Sharp bounds for symmetric and asymmetric diophantine approximation. Chinese Annals of Mathematics, Series B, 32(2), 303–320. doi: 10.1007/s11401–011–0629–4

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In 2004, Tong found bounds for the approximation quality of a regular continued fraction convergent to a rational number, expressed in bounds for both the previous and next approximation. The authors sharpen his results with a geometric method and give both sharp upper and lower bounds. The asymptotic frequencies that these bounds occur are also calculated.


Smeets, I. (2010). On continued fraction algorithms (Doctoral dissertation, Mathematical Institute, Faculty of Science, Leiden University).

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Is there a good continued fraction approximation between every two bad ones? What is the entropy of the natural extension for alpha–Rosen fractions? How do you find multi–dimensional continued fractions with a guaranteed quality in polynomial time? These, and many more, questions are answered in this thesis.

Kraaikamp, C., Schmidt, T. A., & Smeets, I. (2010). Natural extensions for α–Rosen continued fractions. Journal of the Mathematical Society of Japan, 62(2), 649–671. doi: 10.2969/jmsj/06220649

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We give natural extensions for the α–Rosen continued fractions of Dajani et al. for a set of small α values by appropriately adding and deleting rectangles from the region of the natural extension for the standard Rosen fractions. It follows that the underlying maps have equal entropy.


Kraaikamp, C., & Smeets, I. (2009). Approximation Results for alpha–Rosen Fractions. arXiv preprint arXiv:0912.1749.


In this article we generalize Borel′s classical approximation results for the regular continued fraction expansion to the alpha–Rosen fraction expansion, using a geometric method. We give a Haas–Series–type result about all possible good approximations for the alpha for which the Legendre constant is larger than the Hurwitz constant.

Smeets, I., Lenstra, A., Lenstra, H., Lovász, L., & van Emde Boas, P. (2009). The History of the LLL–algorithm. In The LLL Algorithm (pp. 1–17). Springer, Berlin, Heidelberg. doi: 10.1007/978–3–642–02295–1_1

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The 25th birthday of the LLL–algorithm was celebrated in Caen from 29th June to 1st July 2007. The three day conference kicked off with a historical session of four talks about the origins of the algorithm. The speakers were the three L′s and close bystander Peter van Emde Boas. These were the titles of their talks.
 – A tale of two papers – Peter van Emde Boas.
 – The early history of LLL – Hendrik Lenstra.
 – The ellipsoid method and basis reduction – László Lovász.
 – Polynomial factorization and lattices in the very early 1980s – Arjen Lenstra.
This chapter is based on those talks, conversations with these four historic characters, the notes that Peter van Emde Boas and Arjen Lenstra wrote for the preproceedings, and many artifacts from the phenomenal archive of Van Emde Boas.


Kraaikamp, C., Schmidt, T. A., & Smeets, I. (2007). Tong′s spectrum for Rosen continued fractions. Journal de théorie des nombres de Bordeaux, 19(3), 641–661. doi: 10.5802/jtnb.606

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In the 1990s, J.C. Tong gave a sharp upper bound on the minimum of k consecutive approximation constants for the nearest integer continued fractions. We generalize this to the case of approximation by Rosen continued fraction expansions. The Rosen fractions are an infinite set of continued fraction algorithms, each giving expansions of real numbers in terms of certain algebraic integers. For each, we give a best possible upper bound for the minimum in appropriate consecutive blocks of approximation coefficients. We also obtain metrical results for large blocks of “bad” approximations.