Groucho Marx once said, "Outside of a dog, a book is a man's best friend. Inside of a dog, it's too dark to read."
But it is beginning to get lighter in there, thanks to modern cognitive science.
Groucho's quip graces the opening page of "Inside of a Dog: What Dogs See, Smell and Know," a new book by cognitive scientist and psychologist Alexandra Horowitz that goes a long way to suggest what it's like to think with a dog's brain -- to actually be a dog.
Combining new knowledge from hundreds of scientific and animal behavior studies, and mixing it in with a fine style guided by her own loving bemusement of dogs -- especially of her own Finnegan, rescued as a sick and needy pup from a shelter -- Horowitz gives us a fascinating picture of a dog's umwelt (OOM-velt) -- German for "their subjective or 'self-world'."
"Umwelt captures what life is like as the animal," she says.
We met Horowitz and Finnegan on a high plateau -- a grassy field hidden amid a circle of trees in New York's Central Park -- one day at 8 a.m.
There was one hour to go before leash laws came into effect, so we were surrounded by some two dozen joyous dogs of every size, shape, color and pedigree -- or lack thereof -- and as many wakening humans.
Racing around, sniffing, forming little groups and making up games, the liberated dogs turned it into a scene much like any elementary school playground, brimming over with the invention of play -- but play on steroids.
We more static humans stood in their midst, wrapped for a while in dog time.
"Actually, dogs see faster than humans, so to speak," Horowitz, who teaches psychology at Columbia University, told ABC News.
As she spoke, her own Finnegan -- now a fully grown jet black streak of a dog -- zoomed around the outer edge of the field, inveigling a few other dogs into some sort of high-speed canine game of catch-me-if-you-can.
"They have what's called a higher 'flicker fusion rate,'" she said, Finnegan's leash dangling from her hand.
"We see a certain number of what you might call snapshots every second -- maybe about 60 snapshots a second. Dogs send about 70 or 80 images per second, which means that they're seeing a little bit more in every second, a little bit faster in every second than we are.
"Say, a Frisbee; they might see its vector towards its head -- mouth -- a split second before we do."
A human-canine game of Frisbee-catch that illustrated exactly what she was talking about was just taking place out in the field.
A happy dog raced in a blur after a very long throw, and with brilliant split-second timing, leapt into the air, catching up with the airborne spinning plastic disk and grabbing it in its teeth just before it would have hit the ground -- and, the moment it touched down, spun on a dime and headed eagerly back to the thrower.
"At Frisbee, the dog will have you beat every time," she said.
Horowitz also explained how, as she put it, dogs can "smell time."
"Odors exist in different concentrations," she said, as a rumpled white bulldog on the loose started sniffing intently around our feet.
"Tracking dogs can effectively follow an odor path by noticing the difference in concentration from, say, the left footprint to the right footprint," she said.
"The right footprint placed, say, a half second later has a stronger concentration of odors," she explained, "and telling the difference between those two footsteps is a difference in time -- and dogs perceive that."
She went on to explain how dogs, for whom smell is as dominant as sight is for humans, live in a world of constantly fading odor traces -- some near, some far and some up ahead in their near future.
This means, she suspects, that they live in a much larger "bubble of the evolving present" than we do.
However, Horowitz pointed out, contrary to the common notion, dogs' hearing is not far better than ours, and in fact, it's mostly inferior.
"Yes, it's true dogs can hear a slightly higher pitch than we can," Horowitz told us. "But they can't really use hearing to place where a sound is coming from, the way we humans do."
Instead, she explained, while sound may alert a dog to the fact that something is happening somewhere, after hearing it, their brains immediately start searching through input from their eyes and -- especially -- their noses to find out where and what it is.
Challenging a belief so common that it has dug deep into our language, Horowitz expressed doubt about the universal notion of the "alpha dog."
"The wolf research that I've seen doesn't support the notion that the wolf pack is one of domination," she said.
"Instead, it's more like a family unit," she told us, as the leashless dogs still swirled exuberantly around us, forming little groups, checking each other out, forming new groups, and generally energizing the entire scene.
"I don't think that we need to be dominating our dogs," she said.
She describe how both dogs and humans seem, from her research, to naturally conduct their familial behavior -- including how the members of her own young family (including the now leaping Finnegan) related to each other:
"Instead, we are a family together," Horowitz said. "We learn by observing each other; we learn by small punishments, not large punishments -- and by rewards. This is a better model for building a relationship with a dog."
And oh the sadness -- you could see it in their eyes, or at least this reporter would swear you could -- when 9 a.m. tolled and the leash laws came back into effect.
The riot of exhilaration all had to come to heel -- leads clicked on to collars, one by one -- and the human/dog couples made their way, well exercised at least, back through the trees down the paths from the high hidden field to the more restrained streets of the great city.