Gamasutra has an interesting summary of a GDC ’07 lecture by Randy Smith, kick-ass lead designer of Thief 3.
It’s about how to prevent the player from loading too frequently, thus overriding his own actions and damaging immersion, by design rather than restrictions. The main point seems to be that whenever the player takes a loss (to health or ammo in a shooter, for example), he should feel that he has gained more than he lost (by beating a tough boss or somesuch). Interestingly, Smith used Thief as an example of a game where the player is quite inclined to load if he slips up the least bit because regaining what you lost is much more trouble than simply quickloading and trying again.
This is a great point, and explains why I loaded so much more in Splinter Cell 4 than I ever did in Deus Ex. If I get spotted by the guards in Splinter Cell 4, I’ll suddenly have a whole group of enemies searching the area for me, and I must find some place to hide and wait until they go back to their patrols (which is realistic, yet very boring). If I get caught in Deus Ex, I just whip out the ol’ assault shotgun and start pumping hot lead left and right. In a few minutes (of great entertainment!) I’ll have wiped out all the enemies who knew I was there, picked up some ammunition from their corpses, and I’ll be on my merry way again.
Another good point was that if the game systematically provides feedback on the player’s choices, the player will be less inclined to load. This is something SC4 did perfectly: By failing one mission, you often completed another, thus getting the feeling that you weren’t really missing out on anything. Best example is (SPLINTER CELL 4 SPOILER!) after the cruise ship mission when – if you completed certain optional objectives in two previous missions – you’ll get the choice to jam the signal for the bomb, preventing it from blowing up the ship, or letting the ship explode and ostensibly killing hundreds if not thousands of civilians (unless you managed to place smoke bombs in the ventilation, in which case your killcount will be significantly lower – yes it’s that open-ended). If you jam the signal, Enrica – a member of the terrorist organization you’re infiltrating – will be shot right then and there. If you don’t, civilians will die, but Enrica will survive to show up in the climactic second-to-last mission to hand you your equipment, saving you a LOT of trouble later on.
Getting Enrica killed will constitute a huge loss later in the game, but on the other hand you’ll feel like a really good guy, and you’ll get the joy of seeing terrorist mastermind Emile Dufraisne (the bastard) in his worst possible mood.