Cambridge, Mass.—Rich-media ads perform better on social sites than non-social sites when accessed by mobile devices, according to a study by mobile ad-service company Celtra Inc. Celtra's “Mobile Advertising Championship Finals in Engagement” study found that rich-media ads on social sites have four times the engagement rate of rich-media ads on non-social sites viewed on mobile devices. Such rich-media social ads had 16 times higher ad completion rates, two times the engagement time, three times higher video play rates and four times higher share rates than rich-media ads displayed on non-social mobile sites. Celtra's study of rich-media ads, which include such elements as graphics, animation, video, audio or games, was based on an analysis of 32 mobile campaigns in the fourth quarter of last year through the first quarter of this year.