CC. 'Night Flights' thread
I think a combination of all the points are valid reasons for dimming the lights at night, I was told the 'comfort' reason on a BA SEP course many years ago.
I have taken some time to go through various industry papers and studies on evacuation (aero geek that I am), NTSB, CAA, Boeing, Accident Reports etc., and cannot find any particular study on evacuating at night. Although most evacuation studies seem to have been conducted in both day and night conditions.
An interesting extra set of points highlighted in these studies is that;
a) pax will move quickly towards a lighted emergency exit if they are in a dark environment, much quicker in fact than in daylight. And of course the emergency floor lighting is also part of this process.
b) pax will not take so long deciding which exit they are going to use, believe it or not some pax do apparently think 'I dont like the wing exit idea I'll go to the door instead'.
c) pax wont wait behind for their family/friends as they cant see them, apparently many building and aircraft fire deaths occur as people have waited behind for their mates/families.
d) in a smoke filled cabin with lights on the effect is like having your full car headlight beam in fog, you cant see anything, and masks the exit lighting from being seen at a distance.