"Outside of a dog, a book is a man's best friend. Inside of a dog, it's too dark to read." 
 Inside of a Dog is a valuable read for anyone seeking to learn more about our furry companions. Horowitz starts with the basics, focusing on a dog's 
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 and the ways that it differs from a human's. Dogs aren't colorblind, but their perception of color does differ from ours. Scent is far more important in the doggy world than it is to us. Most important of all, dogs and humans simply see different affordances in the objects around them. As Horowitz points out, a dog doesn't see the small matching dog bed as the appropriate place for the dog to sleep. Your bed is just as comfortable, with the added benefit that it smells like you. If you want your dog to sleep in its dog bed, you'll be far more successful if you wrap the nasty plastic-smelling thing in a well-worn blanket. 
 I volunteer in an animal shelter and interact with a lot of emotionally wounded dogs, and I originally picked up this book in my continuing quest to better understand the ways to distinguish submissive behaviours from inviting ones. For example, as Horowitz notes, a dog rolling on its belly can be either inviting a tummy rub or showing submission, and it can be surprisingly challenging to determine which, especially if the dog is already showing many other signs of stress such as "whale-eyes" or tucked tail and ears. While Horowitz does detail these and other signs, I'm not sure I found an answer to this particular question. (My current solution is to make brief contact, then retract my hand and force the dogs to repeatedly re-solicit attention, which they tend to do by crawling towards me and/or pawing my hand. I'm quite sure they find it irritating, but it's kind of cute when they start batting at my hands and mumbling at me.) 
 I also really enjoyed the part where Horowitz talks about doggy play. I am quite familiar with the play-bow, the stance that dogs take to invite rough-and-tumble play. In fact, I've noticed that many humans--myself included--tend to do our own version of the play-bow by slapping our palms on the ground and jerking our necks forward while brandishing a squeaky toy or ball. According to Horowitz, this play etiquette is far more complex than I realized: just as a human abbreviates a joke or a greeting with old friends, dogs abbreviate the play-bows with dogs they don't know and are far more elaborate with those they don't. 
 I mostly enjoyed Horowitz's analysis of the procedures, perils, and pitfalls of the various tests, but there was one case where I think she was dead wrong. The study sought to ascertain whether dogs as a species have an innate drive to rescue their people. The researchers had the owners fake injury or heart attacks, then analysed the dogs' reactions. The dogs tended to be both nonplussed and unworried by their owners' apparent peril, and not a single one tried to seek assistance from the bystanders. From this, Horowitz concluded that doggy rescues are really more of a fluke caused by the dogs' tendencies to want to be near their owners. Given Horowitz's own statements in earlier chapters, I find this reaction rather ridiculous. Horowitz is very clear about dogs' heavy dependence on sound and smell. No matter how dramatically the owners were shrieking, I'm quite sure they didn't smell fearful or injured. To me, this seems like a limited and utterly useless test that tells us more about human assumptions than animal behaviour. 
 However, in almost every other experiment she described, Horowitz did a nice job the ways in which dog behaviour differs from our human expectations, and the reasons behind these differences. In addition to the problematic hero-dog test, Horowitz describes a large set of experiments that attempt to define doggy intelligence in areas such as object permanence or complex emotions such as jealousy or deception. Some of these were both fascinating and illuminating. For example, dogs "fail" various intelligence tests that try to invoke complex reasoning because they tend to go to the humans and ask for help. As Horowitz points out, one could argue that the dogs are performing complex reasoning and tool utilization: they know from experience how to use humans to open refrigerators and cans, so why not get their help in these tests as well? 
 Overall, Inside of a Dog is a great read for anyone who wants to know a bit more about the world their dog inhabits. From understanding play rituals to analysing attention-getting behaviours to dealing with doggy separation anxiety, Inside of a Dog is full of fascinating facts about the curious lives of our canine companions.