|And what was with the Predator's human laugh?|
In the movie “Predator” Dutch (Arnold Schwarzenegger) and his cohorts encounter an alien in the jungle who begins hunting them down one at a time. They try to capture the alien by setting up “trip wires” which the predator cleverly recognizes and avoids. Later on in the film, Dutch dives into a river and gets covered with mud. The Predator approaches him and can’t see him at all depsite being only a few feet away. This implies that the Predator can only see in thermal vision. The cold mud is masking Dutch’s body heat making him invisible to the Predator.
The IMDB page has an entry which claims that in the lore of the “Predator” franchise Predators are equipped with several varieties of sight and thermal vision is just one. That would explain how the Predator was able to get past the trip wires that weren’t visible using thermal vision, but it wouldn’t explain why Dutch was invisible to the Predator. At the time Predator was close to muddy Dutch, he seemed to be convinced Dutch was close so why wouldn’t he switch to normal vision for a second? If he did he would have seen the guy was clearly right there.
It is possible that the Predator switched to normal vision to see the trip wires, but how would he know to do that? Predator didn’t expect to be caught in a net so he probably wouldn’t have expected his prey to be trying to trap him in the first place. Then in the conclusion, Dutch tries to lure the Predator into a final trap with small pointy wooden spears, but Predator sees it despite the fact that he’s been in thermal vision mode the whole time. None of that makes sense, but with a movie like this no one really cares. You can tell the writer was underestimating the audience by making Dutch say “He couldn’t see me” to himself during the mud scene when it’s clearly obvious that’s the case.