Heartthrob Justin Timberlake brought sexy back to his relationship with Jessica Biel this December by popping the question at a vacation spot in Montana, sources confirmed last Thursday.The engagement comes as a bit of a surprise to most of us since the couple split last March after four years together and showed no signs of reigniting the flame.To a psychologist, Justin’s proposal might not be so shocking.

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If you’ve ever had a young child (or taken care of one), you’re likely familiar with a concept called ‘separation anxiety.’ The term describes a phase most children go through where they cry hysterically when mom leaves the room, showing that they feel anxious about when and whether she’ll come back. It’s a totally normal stage that usually passes with time.

But separation anxiety isn’t only reserved for the young. In any close relationship, especially intimate relationships, you are likely to feel some distress when the two of you part ways. If you find yourself missing your partner on a business trip or feeling depressed after a best friend moves to a new city, those are both signs of separation distress.

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Of course, your reaction will look different (you probably won’t scream and wail like a child would). “The analog is really just a lot of sadness, withdrawal, irritability, sleeplessness and loss of appetite,” says YouBeauty Relationship Expert David Sbarra, Ph.D. “It looks like low grade depression.” Those reactions are signs that you cared about the person, or “real indicators of the presence of an attachment,” says Sbarra.

What matters—and what sometimes leads to grand gestures on one knee—is how you interpret your reactions.One theory about how we understand our own emotions holds that we notice our reaction then infer our feelings from that (versus recognizing our feelings then choosing an appropriate reaction). In other words, we look for meaning after the fact.

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To make that more tangible, if you broke up with someone and found yourself crying or feeling depressed, you might infer that you love that person. Maybe you do, or maybe you are just adjusting to a new life alone and mourning the loss of an important part of your life. Either way, the point is that you answer the question, “If I wanted to leave him, then why am I upset?” with the seemingly logical, “I must love him.”

That conclusion isn’t always correct. “The presence of separation distress doesn’t necessarily mean that the relationship is meant to be,” says Sbarra. “Grieving is the natural response whenever we lose someone, even if that is by choice.” In most cases, you may just need a little time.

So now consider that in light of Justin Timberlake and Jessica Biel’s recent engagement. One likely scenario goes like this: Justin and Jessica break up after four intimate years together, then both feel sad and lonely as they try to readjust to single life. Instead of pushing through and moving on, they assume that their reaction is a sign of love (hey, maybe it is) and they get back together, making the pain go away. Because the last breakup was so bad, they assume that their relationship is meant to be and voila, Jess gets a diamond ring.

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While that is one way to get a ring, don’t get any ideas. Breaking up with someone to test his loyalty isn’t the way to forge a lasting commitment. (Not that we’re saying Jessica did that, since they supposedly had a mutual breakup.)“I don’t think that’s a good idea,” says Sbarra. “It seems to me like you’re tempting fate. A better thing to do would be to simply have a conversation about whether or not you’re going to get married. Ask, ‘Do you want to marry me? Where are we going?’ You can read if the person is being true and make your decision.”For those who do decide to commit shortly after breaking up, the road ahead is cloudy. “There’s a danger that you’ll commit when committing isn’t warranted,” says Sbarra. “You could miss the person and commit when it wasn’t really meant to be.”

Perhaps JT and JB really will keep their strings attached for many happy years of marriage, but as of right now, only time will tell.

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