Finger Poke Test

"Scientific test number 1: Poke it."

- Gunnerkrigg Court

Is this thing real? Is that guy alive? Does a component sit in its slot well? Is the dough done? Does the icing for a cake have right consistency? Is this fish hook sharp en-OUGH!.. Every human being seems to instinctively know the default way to find the answers to any of the above questions and much more: poke the object of your doubts with a finger.

Of course, it's also the most common way to find out that the object is too hot, too cold, electrified, consists of flesh-melting goo, etc. Poking many other things is not directly dangerous, but still likely to land the intrepid explorers in hot water far out of their depth. And it's usually not the best way to find out "What Does This Button Do?"

See also Don't Touch It, You Idiot! for cases when it's an obviously bad idea, but someone does it anyway, Finger-Poke of Doom for cases when the catastrophic consequences are applied to the poked object and Giving Someone the Pointer Finger for social related behaviour.

Religion

 * The Bible. When the apostles struggled to believe their own eyes seeing their teacher resurrected, Thomas knew what to do.

Web Comics

 * Freefall has Sam examining fire in microgravity.
 * Gunnerkrigg Court had a moment when Coyote demonstrated how he can "pluck the Moon from the very sky!", holding it in his paw before Antimony. Who responds by poking the ball of pale light with a finger. This left a lasting impression - not only astronomers had to explain what happened, but later disturbed had some questions to ask in the Court.
 * Later Parley tried to touch the Coyote's tooth blade with a gloved finger, but Annie and Kat screamed at her "don't!".
 * Dangerously Chloe had an amusing moment when Teddy grasped the horns of a succubus with two fingers to emphasize his point... let's just say he was entirely unprepared for her reaction - and then, of course, he got slapped. That's on the same day as he grasped an angel's wing (though that time trying to show it to the third party rather than trying to examine it) - so she got flustered and slapped him, with the same wing.
 * Walking CIty flashback about Paradox arriving to the place (spoilers!) - "And this is the set where Paradox touches everything he shouldn't". Short version: a crazy golem just chopped off (and possibly cauterized) the guy's left arm. He blasts the golem... then walks deeper into the city and proceeds to touch every single glowing thingy on his path with his right hand. When we first met him his left arm is prosthetic, but right arm is mummy-wrapped for some reason.

Real Life

 * Finger poke test is common in cooking, though more often than not it's a bad idea - unhygienic, limited to surface (unlike fork poke test), imprecise and/or just asking for local, but severe burns (especialy when hot fat or molten sugar is involved).