  Measuring research impact is important for ranking publications in academic
search engines and for research evaluation. Social media metrics or altmetrics
measure the impact of scientific work based on social media activity.
Altmetrics are complementary to traditional, citation-based metrics, e.g.
allowing the assessment of new publications for which citations are not yet
available. Despite the increasing importance of altmetrics, their
characteristics are not well understood: Until now it has not been researched
what kind of researchers are actively using which social media services and why
- important questions for scientific impact prediction. Based on a survey among
3,430 scientists, we uncover previously unknown and significant differences
between social media services: We identify services which attract young and
experienced researchers, respectively, and detect differences in usage
motivations. Our findings have direct implications for the future design of
altmetrics for scientific impact prediction.
