I would say that it was the other way round. If you are naturally attracted to someone then you put in less effort, as the effort is not necessary when you are doing what comes naturally. It is a completely natural response. However, if you are with someone that you do not find attractive (mentally or physically) you do have to put a lot more effort into it to ensure that they don't feel it or see it in you. I would hate anyone to walk away Reviewom me with a low ego, I want them to be walking on air and whether I fancy then or not is immaterial.
Please do not forget though, that even if there is not physical attraction at first sight, mental attraction is just as powerful and I have had some amazing times with men I have been mentally attracted to and in many cases there has been much more sexual chemistry with men I would not have imagined it possible with at first sight, who have been far better bed fellows than ones I thought I would click with due to physical attraction.
Also, you can become physically attracted to someone due to mental attraction. Of course the person still looks the same, but it's that twinkle in the eye, that gorgeous smile that lights up the room or their gorgeous physique that you don't get to see until the clothes are off. It's like stripping off the layers of an onion and each layer brings new dimensions and potential attraction.
We are very complex creatures and there is often no way of understanding why one union works and another one doesn't, which is why it is such a mine field when punting. You can only do so much to ensure a booking is successful, but now and again with all the research in the world, it just won't work due to a personality clash etc.