Most people know about Pavlov's famous dog experiment where he proved that dogs could be conditioned to anticipate food even when they couldn't see or smell the food. It was a cornerstone experiment in psychology and sounds rather benign.
However, Pavlov was far from a dog lover. Many of his experiments were not done with positive reinforcement like the aforementioned, but with negative reinforcements such as flooding the dogs' kennels and making them believe they were going to drown and conditioning them to be afraid of stairs by repeatedly pushing them down a flight or so. Pavlov's experimentation on dogs may have been cruel, but he wasn't just interested in dogs.
Ideally he wanted to know how the human mind worked so he acquired himself some children from the local orphanage - you know, impressionable minds who didn't have a parent to stand up for them.
He conducted the same salivation experiment on the orphans as he did on his dogs, the only catch was orphans aren't as willing as dogs to receive food from strangers. So he strapped them down to a chair, taped their mouths open, inserted a device to measure their saliva, and proceeded to force feed them both sweets and bad tasting things. This all sounds like the beginning of a bad alien abduction movie.