Footnotes

• Contributors CPFO'D devised the experiment which was carried out by RTJ and LEG. RTJ and LEG carried out the experiment. RTJ performed the statistical analysis and wrote the manuscript, with assistance from CPFO'D. All authors provided input in terms of feedback and reviewed the manuscript prior to submission. RTJ acts as the guarantor.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Not commissioned; internally peer reviewed.