Human computation is a computing approach that draws upon human cognitive
abilities to solve computational tasks for which there are so far no
satisfactory fully automated solutions even when using the most advanced
computing technologies available. Human computation for citizen science
projects consists in designing systems that allow large crowds of volunteers to
contribute to scientific research by executing human computation tasks.
Examples of successful projects are Galaxy Zoo and FoldIt. A key feature of
this kind of project is its capacity to engage volunteers. An important
requirement for the proposal and evaluation of new engagement strategies is
having a clear understanding of the typical engagement of the volunteers;
however, even though several projects of this kind have already been completed,
little is known about this issue. In this paper, we investigate the engagement
pattern of the volunteers in their interactions in human computation for
citizen science projects, how they differ among themselves in terms of
engagement, and how those volunteer engagement features should be taken into
account for establishing the engagement encouragement strategies that should be
brought into play in a given project. To this end, we define four quantitative
engagement metrics to measure different aspects of volunteer engagement, and
use data mining algorithms to identify the different volunteer profiles in
terms of the engagement metrics. Our study is based on data collected from two
projects: Galaxy Zoo and The Milky Way Project. The results show that the
volunteers in such projects can be grouped into five distinct engagement
profiles that we label as follows: hardworking, spasmodic, persistent, lasting,
and moderate. The analysis of these profiles provides a deeper understanding of
the nature of volunteers' engagement in human computation for citizen science
projectsComment: 3 tables, and 4 figure