Copycatgedrag bij terroristische aanslagen: Een verkenning

Translated title of the contribution: Copycat behaviour in terroristic attacks: An exploration

Kees van den Bos*, Liesbeth Hulst, Iris van Sintemaartensdijk, Benthe Schuurman, Mariëlle Stel, Maaike Noppers, Beatrice de Graaf, Amarins Jansma, Carla Spiegel, Marleen Haandrikman, Lotte Manshanden

*Corresponding author for this work

Research output: Book/ReportReportAcademic

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This exploratory report examines copycatting behaviour following terrorist attacks. This concerns behaviour that someone performs intentionally and in a motivated way to imitate a certain predecessor, particularly a person or group who was noticed in media reports for committing a terrorist attack. Distinctive about copycatting behaviour is that it is not directly controlled by a terrorist group, but that people themselves decide to imitate an attacking person or group of persons.

The reason why this report was written is that copycatting behaviour can increase the chance of a future terrorist attack. Copycats can be inspired to copy the ideology and/or the methods of previous attackers and possibly even surpass the number of casualties of the earlier attack. Such behaviour can increase the number of people who fall victim to terrorist attacks and can create feelings of terror in the general population. However, there is not yet definitive evidence for the role of copycatting behaviour in terrorist attacks. This is why this report was considered to be important. Chapter 1 explores the reasons for the report in more detail.

For this report, interviews were held with eight national and international experts in the field of copycatting behaviour and terrorism. These interviews are discussed in Section 2.4. The list of topics discussed with these experts is included in the Appendix 1. Furthermore, two literature studies were conducted. The first literature study focused on copycatting behaviour in terrorist attacks. This study resulted in 36 publications in this field. The second literature study focused on copycatting behaviour in other fields than terrorism, like suicide and school shootings. This resulted in 44 publications. This body of literature is complemented with suggestions from interviewed experts and members of the guidance committee. The method of the literature review is discussed in Section 3.1. The most important studies that were found in our literature search are summarized in Appendix 2. A concise social media analysis was conducted as well. This analysis was limited in scope. The box at the end of Chapter 3 discusses the main points of this study. The report also analysed terrorist threat assessments of the NCTV, annual reports of the AIVD, and documents of the Netherlands House of Representatives that included terms related to ‘copycatting behaviour.’ These insights were complemented with insights into the strategies used by other countries to counteract copycatting behaviour and the interviews with experts. The findings of this literature review are discussed in Chapter 4. Section 5.2 discusses limitations of the conducted literature studies, interviews, and the social media study. This results in avenues for future research.

Definition of copycatting behaviour
An important aim of this report was to develop a working definition of copycatting behaviour, which can be used in studying and addressing copycatting behaviour in terrorist attacks in policy and in practice. This definition is mentioned in the first
paragraph of this summary. In Chapter 2, components of this definition are discussed, based on the literature examined and the interviews held with experts in the field of copycatting behaviour and terrorism. In that chapter, it is noted that copycats feel encouraged to imitate a method from a previous terrorist attack. Terrorist attacks can also inspire copycats to take over their predecessor’s ideology. The imitated behaviour often concerns violent behaviour and can also include non-violent behaviour. Copycatting behaviour often occurs because people identify with a previous attacker. Copycatting behaviour can also occur because people agitate against a terrorist act from ideological, religious, or other movements which oppose their views.

Evidence of copycatting behaviour
It turns out to be difficult to determine the exact role of copycatting behaviour in terrorist attacks. In Chapter 3, the evidence of copycatting behaviour following terrorist attacks is discussed. Copycatting behaviour in other fields, such as suicide and school shootings, are also discussed.

Addressing copycatting behaviour
What can be done about copycatting behaviour following terrorist attacks is an important question. In Chapter 4, relevant Dutch publications are studied to answer this question. Publication studied include the terrorist threat assessments of the NCTV and the annual reports of the AIVD in which copycatting behaviour is discussed. Other countries also provide illustrative insights as do interviews with the experts. Based on these insights, the conclusion seems warranted that suggested approaches of counteracting copycatting behaviour are in line with the existing core components of Dutch policy, such as the personal approach and the integral approach.

Each chapter in this report includes concluding sections at appropriate times. For details, the reader is referred to these sections. Chapter 5 presents a general conclusion for policy and practice (5.1) and future research (5.2). An important general conclusion based on the presented literature studies, interviews, and the social media study is that copycatting behaviour in terrorist attacks can occur. It should be noted, however, that terroristic behaviour in specific cases often entail various factors that, combined, led to the behaviour. Interpreting a specific case therefore requires an individual approach, tailored to the precise case under consideration and the specific details relevant in that case. Some useful ideas have been developed in preventing and addressing copycatting behaviour in terrorist attacks. These ideas are in line with Dutch policy and practice in the field of counterterrorism and prevention of radicalisation. Continued investment in social networks and a personal approach to radicalization is particularly important in this respect. Media reports can increase the chance at copycatting behaviour. It could therefore be helpful if the media themselves, without affecting the freedom of the press in any ways, would decide to hold back in their reports on terrorist attacks. Reporting no or few details about the exact methods used decreases the chance of a method of a previous attacker being copied. Holding back in reporting on personal details about the attacker also helps as it decreases the chance of identification with the attacker and his/her ideology. It is important to continue working on a coherent, substantive vision on radicalisation and (counter)terrorism, including copycatting behaviour. Copycatting behaviour is not about following instructions on what to do, but about what people decide to do themselves. This motivated behaviour can be impulsive and occur in a whim. To interpret this behaviour, it is important to carefully analyse what people think, feel, and actually do. We are pleased to note that the Dutch policy in the field of counterterrorism and the prevention of radicalisation is paying appropriate attention to these points for some time now.
Translated title of the contributionCopycat behaviour in terroristic attacks: An exploration
Original languageDutch
Place of PublicationUtrecht
PublisherUtrecht University
Number of pages85
Publication statusPublished - 20 Aug 2021

Publication series

NameWODC rapport
PublisherWetenschappelijk Onderzoek- en Documentatiecentrum (WODC)


  • Terrorism
  • Delinquents
  • Offender characteristic
  • Criminal psychology
  • Delinquent behaviour
  • Attack
  • Counter-terrorism
  • Suicide
  • Agression
  • Jihad
  • Right-wing extremism
  • Fire-raising
  • Media
  • Motivation
  • Prevention
  • Modus operandi


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