The change_focus gene lets MyKaryotes change whatever their current focus is on. As you may recall, MyKaryotes can only focus on one object in their environment at a time, and this focus lets them carry out actions relevant to that focus.
The first and only argument to the change_focus gene dictates what the MyKaryote should change its focus to. Below is a table showing all of the possible strings for this argument.
Note that these focus changes will only be successful if an object of that type is within the cell's eyesight range attribute, as measured in pixels. If it can't find any, then the focus will be set to noone.
1 change_focus nearest_prey 0 0 0