I've been deliberately NOT forming mental pictures, OG. Long experience has convinced me that people in reality are always much nicer, and different from, my imagined version so I don't do it any more. (I think it began when I started work at a radio station some years ago and was astounded to discover that the dark brown, authoritative voice that read the lunch time news emerged from a spotty, skinny and shy 20 year old and the film reviewer who sounded like a ditzy 18 year old was actually a serious retired head teacher in her late 50s... and so on
)