That article is nothing but sensationalist.
Dave s/g is right (hold the phones!) that volts means nothing. You could have 0.05 amps driven across 400V; or 5 amps driven across 100V - the latter is far more dangerous.
You can even buy 'games' - aimed at the gadget obsessed trendy male - where laser-activated guns and chest packs administer mild shocks of many volts to the user.
The reason I mention all this is because, as someone who knows the parameters of the 'torturing' medium, I would not have the same reservations about pressing the 'bzzzzt' button than others.
And yes, people do care far more about animals than humans. Although the human race at times sickens me, and there are some freakishly disgusting examples...
On the whole, value of life must be measured on level of sentience. As a human is a more sentient being than a dog, then if for whatever reason a choice must be made between the two, the human must be saved ahead of the dog.
EDIT:- I am trying to make the point that in my case, I would KNOW that voltage is not the indicator of deadly torture and hence would not believe I was killing the participant.
Also, it does not shock me that people did pursue the scale right to the end of 450 Volts. There are a multitude of tests available that show the lengths another human will obey one he believes is in authority - these tests show that in many cases, human 'subjects' have the uncanny ability to suspend their logic and emotion when under the command of another, whom they believe to be in total authority.