Google Analytics recently launched a set of Social Engagement reports which helps you understanding user behavior of visitors who +1 your pages compared to the users who don’t. Google Analytics automatically reports all the clicks on the Google+1 button. With the help of Social Plugin Tracking in Google Analytics you can analyze how the content is being shared by all the social media buttons like “Facebook Like”, “Twitter Tweet” & “Google+1”.
Social Engagement Report is basically set of 3 reports which are available under VISITOR > SOCIAL section of the new GA interface.
Visitor > Social > Engagement: Helps you compare visits which included social action against the visits which did not had any social action.
Visitor > Social > Action: This report helps you comparing the social interactions based on their source. For example: You can compare Facebook Interactions & Twitter Interactions.
Visitor > Social > Pages: With the help of this report you can see number of social actions on each page of the site and this can also be grouped based upon the social media source.
You can set up Social Plugin Tracking by following the simple steps mentioned here: Setting Up Social Plugin Tracking