For the UKCAT having a good sense of spatial awareness and logic can get you through but for the BMAT you do need to be good at science for the science section, There are people who can get all A* and have average intelligence ( im talking about IQ) - It also comes down to the mental state of that person on that particular day. IE- Tired, motivated, hyper .... to end, there are many many factors but I do believe for the UCKAT in particular that if you have high intelligence you will do well as a lot of the content is the same as the mensa test ( such as shapes, reasoning etc)