I'm trying to identify a short story I read as a teenager about a kind of alien tunnel or cave that the government is investigating. They keep sending volunteers in and each one gets killed unless they do certain things like walk forward then backwards or hold their arm above their head. Through trial and error they figure out about half the tunnel, then they get a super agent to try and figure out the rest. I apologize if my description is sketchy or outright wrong. This was a long time ago.
One of the analogies in the story was that if a bug accidentally crawled into a can, it wouldn't understand why it would be harder to walk side to side rather than straight forward, or that the solution would be to turn around.