I like it when animals behave like humans. But I find even more fascinating those human behaviours that do not have an animal equivalent: they shed light into how humans are very special animals after all.
In my family we have had dogs since I was 10 and I have enjoyed many of their human-like behaviours. One that has always impressed me is their guilty look when they have done something naughty when left alone in the house (there are entire compilations online devoted to this genre).
However, there is one scenario where that cute guilty look doesn’t really play out in the way it would with humans: when we leave multiple dogs in the house (yes, there are multiple) and only one has done something naughty (say, it chews toilet paper in the bathroom), then only that dog looks guilty when we arrive back. This happens with my mother’s two dogs (Sushi and Trilly) and I always find it comical how the naughty dog (typically Trilly) would reveal itself without even trying to play dumb, which is what a child would do. After all we have no way of knowing which dog chewed the toilet paper!
Are dogs incapable of being deceptive?
The real explanation is actually more interesting and I came across it recently while reading this passage from the book “Knowledge: A Very Short Introduction” by Jennifer Nagel (emphasis mine):
“… human beings can also keep track of the ways in which others are mistaken, and this is something that no other animal does (as far as we can tell). You can see another person as having a false belief: playing a practical joke on a friend, you empty his cereal box and fill it with rubber insects. You know, as you watch him sitting down at the breakfast table, that he is expecting cereal to pour from the box. You know that he has an inner representation that doesn’t match the actual outer reality. No other animal seems to be capable of representing this kind of state, even in situations in which it would be highly advantageous. In experimental tests of whether an animal can keep track of another’s false belief, all non-human animals fail.”
What an elegant explanation for Trilly’s behaviour! The naughty dog has no way of understanding its owner’s state of mind of being mistaken or uncertain about the culprit1. It just implicitly assumes the owner will know what the dog knows, i.e. that it is guilty!
Knowing that someone else is wrong – and taking advantage of it – is a very sophisticated cognitive process, and uniquely human. Such a crystal clear demonstration of this has been playing out all along right in front of me, every time Trilly chews some toilet paper.
 Dogs don’t have a theory of mind, to use the technical terminology.