There was an interesting test done some years ago which was much more realistic.
The aim of the "standard" test is to get everyone out in 90 seconds. To this end, everyone contributes to the task and helps everyone else to achieve the goal.
In a real accident, the goal is to get YOURSELF (and maybe your family) out and to hell with everyone else. To try and simulate this, the "pax" where told that only the first third of the group out of the aircraft would get $50. The remainder would get nothing.
The result of the test was significantly different to the "standard" with a much longer evacuation time.
Can't remember who carried out this test and maybe I have some of the numbers wrong but the principle is there. I also seem to remember a test when all the cabin crew jumped first and left the "pax" to themselves. can't remember the result of that one. Can anyone provide further details?