If you have a crush on someone you usually want to find out if they have one on you too. In my opinion outright asking them is often not a good solution, because if they don't have a crush on you yet it decreases the chance of this ever happening if they know you have one. This believe is based on what I read about love psychology. Hovever I don't really want to discuss the option of outright asking them in this thread, therefore I have not elaborated further how I got to this believe.
The alternative to asking them is trying to interpret signals that they might give you. However to know how many signals you need before you should believe that they are in love with you, you would need the prior. I have not been able to find anything about the prior of someone being in love with you. Therefore my Idea is to do a survey in order to find out how likely it is that a person you know has a crush on you. The plan is to ask the person taking the survey how many people they know well enough to possibly have a crush on them and how many people they actually have a crush on.
I have created a Survey for this and would be really happy if you would participate.
The next stepp would be to discuss how certain signals a person can give you raise the probability of them having a crush on you. That part is quite difficult. I think probably the best way would be to check how your friends react to certain situations and what body language they show you and then, if you find out someone has a crush on you, to look up what he did differently from people who are merely your friends. I am currently not in a good position to do this experiment but if someone wants to try or has results about this to share please do so. However I think this part is less important than finding the prior, because most people have at least a general idea about what certain signals mean from personal experience while at least I have no idea at all what the prior might be.
Here a poll corresponding to the survey as proposed.
I took the freedom to extend it somewhat.
How many people do you know?(*) [pollid:965]
*) People you know for the purpose of this question are those you know well enough that you could have a crush on them. As a reference take people whom you have seen on more than 5 days in the last half year and had at least 5 hours of private conversation during that time. Please only count the people of a gender you are interested in. Do not include family members. (no, I can't offer a "see results" on this one, and please don't choose 0)
How many people do you currently have a crush on?(*) [pollid:966]
*) The definition for having a crush on someone is that you find that person attractive and could imagine being in a relationship with him/her. If he/she would ask you out for a date and you were not currently in a relationship you would say yes.
Compare to wikipedia on infatuation.
What gender do you identify with? [pollid:967]
What gender are you interested in? [pollid:968]
Extra questions:
As I think that having crush is somewhat weak (weak enough to have a crush on multiple people). Thus I additionally propose this:
Have you currently fallen in love with someone (*)? [pollid:969]
*) For 'fallen in love' see wikipedia on limerence for reference. The carried away, rose-colored glasses, heart skips a beat thing. This is apparently an exclusive state (single person) in human bonding.
With how many persons have you ever fallen in love with? [pollid:970] (guess if necessary, 0 if unsure)
Guess a range: How many persons on average does it take to fall in love with once(*)?
The average is at least [pollid:971] (set 0 if unsure or see results)
The average is at most [pollid:972] (set 1000000 if unsure or see results)
*) Persons counted as in the first question. The population average is meant not your personal average.
Guess: Among how many persons on average there is one an average person could get a crush on(*)?
The average is at least [pollid:973] (set 0 if unsure or see results)
The average is at most [pollid:974] (set 1000000 if unsure or see results)
Do you think that the average number is [pollid:975]