Your love-struck friend will wonder if you feel the same way, and will probably dream up subtle tests to find out. They could save themselves some effort by quickly surveying the scientific literature, though, because they will almost certainly be following one of seven well-trodden paths.
1. Endurance This is most common type of test. In this category, the love-struck friend does their best to test the other person's feelings by fishing for compliments or demanding help – especially if it comes at a cost to the other.
A classic endurance gambit is the self-put-down. As one respondent recalled: "He was really getting down on himself, saying he wasn't a very capable or nice person. He said it to get me to compliment him and verbalise how much I thought of him."
Another type of endurance test is called forced choice, in which your friend wants to see if you will drop everything for them. "She came to where I work out and said that she was really depressed but didn't want to bother me," said one man in his interview. "She really wanted to see if I would stop what I was doing and show my concern, indicating how much I care for her."
Finally, enamoured friends will behave like spoiled brats, pushing their friend's buttons to see how much mistreatment they will put up with without complaining – will you still like them even when they're being a pain?
2. Triangulation The second most popular type of test was dubbed the triangle, because it relies on the age-old saying "three's a crowd".
Some people engineer "fidelity checks", especially if the relationship has already strayed beyond the platonic. One of the interviewees wanted to test if her boyfriend was as keen as she was. "I would intentionally leave him alone with my room-mate and then ask him when I returned 'What have the two of you been up to?' If he acted uncomfortable, I would know that he wasn't faithful – or at least that he was thinking about being unfaithful to me."
Others employ jealousy tests: "I tested her limits by going out with other women and making sure that she found out about it. I wanted to know what kind of relationship commitment she wanted," said one man.
3. Hint, hint Then there are the indirect suggestion tests: joking about serious feelings, hinting or getting increasingly intimate with bodily contact. "When we were just becoming romantic, he kept getting more and more bold with his touching – first his arm around my shoulder, then moving in real close, etc. He was waiting to see if I would tell him when to stop as a sign of how much I liked him," said one interviewee.
4. Miss me? Distance is supposed to make the heart grow fonder, and indeed physical separation is a common test. One respondent admitted: "To see if our relationship was really strong I tested it… by going overseas for a few months."
If you have felt like you didn't want to be the first to call, you could be using another separation test called initiation induction. "When I returned from Switzerland, he didn't call me even though he knew exactly when I was returning. He wanted to see if I still felt the same way about him by calling him first," one woman recalls.
5. Heart to heart The directness test is really the opposite of a secret strategy. Far more popular with men than women, it involves either asking a person straight out how they feel, or speaking openly about yourself in the hope your love interest will too.
"I was having trouble getting him to open up to me about his family and his background," one woman said, "so I started talking about my folks and sisters, hoping that he would reciprocate and tell me about himself as a sign that he trusted me and wanted me to know more about him."
6. Inside information Ever tried to find out from someone's friends whether they might have a crush on you? Then you have employed what Baxter and Wilmot aptly call asking third party tests. It might sound like playground behaviour, but grown-ups do it too.