Illusion Logic?

Can someone explain to me the logic behind these illusions where a girls goes in a box, the magician thrusts several sharp objects through the box, and then he opens the door to reveal she's not in there any more?

Any sense of danger the audience felt for the hapless assistant has now gone and they are left with a feeling of having been tricked. But not tricked in a good way, more in a here's-a-present-for-you-but-when-you-open-the-gift-it's-an-empty-box kind of way...

I have a solution to revamp these illusions and eliminate this feeling but so far none of the illusionists I've talked to are interested. I guess the status quo is good enough for them.

I wonder when someone will do a study of what people are actually thinking while watching a magic trick, moment by moment. Would be very interesting and I think very educational for magicians. (But I'm not sure they really want to know...)

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