First Online: 30 October 2019
Compliance with Ethical Standards
: <b>Funding</b>: The support of Leiden University is kindly acknowledged.
: <b>Conflict of Interest</b>: Matthijs van Haren declares that he has no conflict of interest. Nathaniel I. Martin declares that he has no conflict of interest.
: <b>Ethical Approval</b>: This article does not contain any studies with human participants or animals performed by any of the authors.