For 10 seconds, turn off your computer monitor. (then turn it back on to continue reading) Do it. I am being serious.
If, as soon as the screen went blank, you did not feel like you just awoke from a trance, and you did not feel more alert, you are either lying or you have a well-behaved monitor.
A conspiricy theorist would say that the refresh rate on computer monitors is deliberately low in order to stupefy us into doing things we would not normally do (like buy £300+ mp3 players on amazon)
I didn’t feel like I woke up out of a trance. Granted, I did pay a little more attention to my surroundings. But that happens whenever you’re paying close attention to something and then do something else – like when you walk out of a movie theater, finish watching TV, or finish drawing/reading/making origami/masturbating :D/whatever. My refresh rate is 60 Hz.
That’s nothing – try doing them all at the same time. Then you’ll feel like you woke up from a trance, I guarantee you.
As for the OP, I find my post-computing mental state greatly depends on what I’m doing with the computer, which makes the refresh rate (or related theories) highly unlikely.
When I get turn off my monitor and stand up, I often notice that I’m temporarily “blind” in my dominant eye – (that is, everything appears much darker through that eye.) This messes with my depth perception and is slightly disorienting.
If you really want to trance out on your monitor, look here.
Nope, no trancy or alerty sensations here. But that’s probably because the screen on my monitor is piss-yellow for around 80% of the time, so I sort of feel relieved when I turn the damned thing off.