Why do pupils dilate in response to emotional state? I just came across an article on the internet stating that,


  Pupils dilate when we find someone or something attractive.


So, as far as I know, this kind of dilation doesn't seem to have any effect on attractiveness of subject, does it?

For example:

Suppose if a one person A in love with person B, and pupils of A tend to dilate when seeing B, What effect does it have on B? Any psychological effect perhaps?

P.S. I'm not sure if this should be on Cog.Sci
The dilation of the pupil is under control of the sympathetic nervous system. The main role of the sympathetic nervous system is to get the body ready for fast response. The typical example is the 'fight-or-flight' response, but that can also occur in the presence of a potential sexual partner. Therefore, dilated pupils can be a sign of sexual arousal. 
Now, that's the response of the person showing the dilated pupils, but your question related to the effect on the other person. People with more dilated pupils are rated as more attractive by observers unaware of this manipulation Tombs &amp; Silverman, 2004 - at least for males looking at females. As an aside, people in ancient Egypt are said to have used atropine, which is a poison extracted from the belladonna plant, as a cosmetic to artificially dilate their pupils.