A table entitled ‘Levels of participation and engagement (adapted from Sui et al., 2013)’. An arrow passes from Level 1 at the bottom of the table towards Level 5 at the top. This arrow is accompanied by the text: ‘Increasing levels of citizen participation and engagement’. Level 1 is labelled ‘Crowdsourcing’, Level 2 is ‘Distributed Intelligence’, Level 3 is ‘Participatory Science’, Level 4 is ‘Extreme Citizen Science’ and Level 5, which appears in parentheses, is ‘Citizen Social Science’. A series of bullet points sit alongside the levels, but they are not allocated precisely to each one. Six bullet points span the lowest four levels, from the bottom upwards these are: Volunteered computing; Citizens are sensors; Voluntereed thinking; Citizens as basic interpreters; Participation in problem definition and data collection; Collaborative science-problem definition, data collection and analysis. One bullet point is separate from others and is associated with Level 5: Citizens as key agents of research, action AND policy change at ALL levels of engagement and scales of decision-making process.