Below is a repost, with relevant video from Desmond Morris
The advantage to learning to be emotionally open and capable through practices such as deliberate romance, improvisational music, chi-kung, bodhicitta generation and group socializing is that you can learn to feel love at will, which will dilate the pupils.
This has a large influence on the person you are talking to. It can make them open up emotionally very fast.
When combined with displays of creativity, interpersonal and social ease and respected dominance, large pupils are hypnotic.