We address the question of whether altmetrics data can provide both convergent and discriminant validity for assessing societal impact. Using data from the UK Research Excellence Framework (REF)... Show moreWe address the question of whether altmetrics data can provide both convergent and discriminant validity for assessing societal impact. Using data from the UK Research Excellence Framework (REF) and the company Altmetric, we investigate whether or not societal impact can be indexed by using altmetrics. Our results reveal that paper mentions on Facebook, in blogs, in news, in Wikipedia and in policy-related documents are indeed convergently and discriminantly valid, i.e. is valid as a discriminant indicator. The results for Twitter reveal that the source does not seem to be valid for societal impact assessment. Show less