What is the imagery in the poem EMBRACE by Billy Collins?

The imagery in this poem is simple, yet insightful: the image created is just as it describes, a person with their arms wrapped around themselves so it looks like someone is in front of them holding them in an embrace. The image works so well because just about everyone has done this as a child or young adult. The more mature comment on this "parlor trick" is the insight that when you do this it's really rather pathetically sad...because by closing your arms around yourself you're not able to really hold anyone else, and the thought that only you would embrace you that way is painfully lonely. The comment about the straight jacket is another good image, because your arms are in the same position if you're wearing a straight jacket...something reserved for those who've gone over the edge, and of course, being too alone could get you there too. So those are the two images: the lonely embrace and the fitting for a straight jacket.