Factual error: When the infected Palmer starts his transformation into the Thing, he has a series of fits and the creature 'falls', or leaps upward onto the ceiling. Watch closely...you can see a piece of paneling also 'fall' upward, when it should have fallen down. (01:23:20)
Continuity mistake: When Mac is locked out of the complex by the rest of the team, who think he may be a 'Thing', Childs uses an axe to try and chop open one of the doors, leaving a HUGE hole in the middle of it. Later Childs returns to that same door and the hole is significantly smaller and at a completely different location on the door.
Continuity mistake: When the crew is outside and they're going to lock Blair in the tool shed, you can see someone nailing wood across the window on the front of the shed. The pieces of wood are horizontal. In the next shot (inside the shed), if you look at the window in the background, the strips of wood are vertical. When Mac goes back outside, the wood is horizontal again.
Answer: Remember that he'd just spent the whole day investigating how something mysterious and horrible destroyed the Norwegian camp, so he's already in a spooked state of mind. Hearing the dogs screaming at night is already unusual on its own, and also reminds him how this whole episode all started with a crazed Norwegian trying to kill a dog. Deep down he knows whatever happened to the Norwegians is now starting at their own camp.
TonyPH
I 100% agree.