Let's say someone is(on foot) on the way to the supermarket, and then realized he let his wallet at home: <br/><br/>"He doubled back."<br/>"He doubled back on himself ."<br/><br/><a href='http://www.macmillandictionary.com/dictionary/british/double-back' target='_blank' rel='nofollow'>http://www.macmillandictionary.com/dictionary/british/double-back</a><br/><br/>Any difference between "double back" and "double back on oneself"?