From Media Post:
According to The Harris Poll in November 2012 there are both divergences and similarities in actions performed by smartphone owners using both the phone and the computer. When smartphone owners are asked which of a set of actions (common to both devices) they regularly perform on a smartphone and/or on a computer, the IM, or instant message is the most common smartphone use (87%) and the least common use for a computer (20%).
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See Also: Additional Findings from the Report Referenced In the Article (via Harris Interactive)