fly
Your friend is indeed correct, they are called 'cognitive' tests, or at least the verbal, numerical and spacial/ diagrammatic tests are. I have not heard the personality profile referred to as such in that it is not a test of learned skills or applied knowledge, it's about preferences.
So with the personality profile you are correct; just be honest and your profile will be accurate (within the limits of the test!)
The other cognitive tests however are all about knowledge, learned, applied, percieved, visualisation etc etc. There is no need to be honest and see what happens with these......you can do an awful lot of preparation for these to dramatically improve your scores, so if you are to sit a selection that utilises these tests do get online and sit the many free ones, go to the library and spend a few hours running through examples and looking back to see where you went wrong. It will be time well spent and may make the difference between pass and fail.
Best of luck,
PP