⁣Here are the sources for anyone who wants to read about them. Just look them up via peer-reviewed journals database like google scholar:

1) prolonged eye contact = stronger attachment and increased affection (Kellerman, Laird, et al, 1989)
2) "opposites attract" - women are naturally more attracted to those with different HLA-complexes (genetic blueprints) (Kromer, Hummel, Croy, et al, 2016).
3) children with older parents go on to find older people more attractive when they're adults (Perrett et al, 2002).
4) those with symmetrical faces tend to be viewed as more attractive (Grammer & Thornhill, 1994).
5) both sound and smell play a part in attraction (Groyecka et al, 2017).
6) we're attracted to those of a similar height to us, due to genetics (Tenesa et al, 2016).
7) the color red makes women more attractive to men (ScienceDaily, 28th October 2008).
8) filling in love releases chemicals that make us feel good, cheeks flush, palms sweat and heart race (ScienceDaily, 6th Feb 2014).