In fact, the high resolution graphics of more recent MMOs have made the virtual world experience less immersive, Bartle says.
"In a graphical world, you're reliant on what your senses tell you," he explains.
"If you see a big, scary dragon, then it's only as big and as scary as the artists and animators could make it. It might scare some people, but not others. When you read a description of a big, scary dragon, you construct the image in your own imagination. It's personal to you.
"What you see in your mind's eye is what's big and scary customised for you. It's far more believable than anything even photo-realistic graphics could give you."
A side-effect of graphics is that virtual worlds that rely on them are able to offer far less detail than text-based MUDs: "The physics of [text-based] MMOs was deeper, which meant that you weren't jolted out of your immersion when something that ought to happen didn't, or something that should be possible wasn't.
"Example: My WoW warlock carried a glass of cold, fresh milk around in her backpack for five years. She swam across rivers with it. She got squished by dinosaurs with it. It was never affected. It never went off, it never spilled. However, had she tried to pour half of it into another glass, she couldn't have done so. All she could do was drink it, or use it as some ingredient in cooking.
"There are a myriad of these kinds of dissonances. How come I can see a bunch of orcs down the corridor but when I slaughter their colleagues in front of their eyes they don't even look up? Can't they see me? Can't they hear those fireballs that are shaking my headphones? Why don't they either rush to help or run away? They just stand there!
"And then, when I kill them, I find that one of them was carrying a kick-ass axe but for some reason he chose to use the ineffectual hatchet he had instead - which I can't pick up as it's mysteriously disappeared.
"All this extra level of detail was in the better MUDs, but we don't see it in MMOs because it's too expensive to animate it all."
Bartle sees the growth of 'free to play' (F2P or 'freemium') MMOs as having a bigger impact on virtual world design than the emergence of mobile gaming.
"I don't think that we're going to see MMOs morph into apps any time soon, for the simple reason that if something is so engrossing that you'll play it for 2-4 hours every night for months on end, you're not going to be able to do that on a phone.
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