In a highly flirtatious situation like this Anders barely had to try to exert his power, it just sort of happened automatically. The fact that it didn't work on Ruby was interesting and the fact that she still seemed to enjoy the feeling was even more interesting to him.
"Mmmm well, confession time for you...What are you that my power doesn't work? Maybe if I like what I hear then I'll keep it up as long as you like." He smirked.