We take the magical gift of consciousness for granted. From the time I awaken until I fall into a deep, dreamless sleep, I am flooded with conscious sensations. And contrary to assertions made by philosophers, novelists and other literati, by and large this stream of consciousness does not relate to quiet self-reflection and introspective thoughts. No, most of it is filled with raw sensations.
Two weeks ago a friend and I climbed a sea cliff above the Pacific surf at Malibu, Calif. When I am on the sharp end of the rope, my inner critic—that voice in my head reminding me of deadlines, worries and my inadequacies—is gone, is silent. My mind is all out there—conscious of the exact orientation, shape and texture of the rock, looking for tiny indentations where I can get purchase for my fingers and toes, always aware of how high I am above the last bolt. One moment I am exquisitely aware of my feet on all too smooth rock, reaching upward with my left hand for a handhold. The next I am airborne, my right hand bloody, my right rib cage aching. After catching my breath and shouting to my anxious belayer that I’m okay, I am filled with adrenaline for having survived yet another fall, can’t contain my enthusiasm, and scream.
Today only the bruised rib remains as a testament to how much of the stream of consciousness is pure sensation. Whether you are weaving on a motorbike through flowing traffic, running in the mountains, dancing to fast rock and roll, reading an engaging book, making love or debating with your friend, your eyes, ears, skin and body sensors paint an engrossing picture of the outside, including your own body, onto your mind’s canvas.
I suspect this feeling is not that dissimilar to the way animals consciously experience their world. Except perhaps for the great apes and a few other privileged big-brained animals, most species do not posses the highly developed sense of self, the ability to reflect on oneself, that people have. Most biologists and pet owners are willing to grant consciousness to cats, dogs and other mammals. Yet our intuitions fail us completely when we consider fish and birds, let alone invertebrates such as squid, flies or worms. Do they experience the sights and sounds, the pains and pleasures, of life? Surely they can’t be conscious—they look too different from us, too alien.
Insects, in particular, were long thought to be simple, reflexive creatures with hardwired instinctual behaviors. No more. Consider the amazing capabilities of the honeybee, Apis mellifera.
Martin Giurfa of the University of Toulouse in France and Mandyam Srinivasan and Shaowu Zhang, both at the Australian National University in Canberra, trained free-flying bees, using sugar water as a reward, in a variety of complex learning tasks. The neuroethologists taught the bees to fly in and out of tall cylinders with one entryway and two exit holes. Each bee had to choose one of two exits to leave the cylinder and to continue her flight. (In bee colonies, males are a small minority and do only one thing—and that only during the virginal flight of the colony’s queen.)
These cylinders were staggered into mazes with multiple levels of “Y” branch points that the bees encountered before reaching the desired feeder station. In one set of experiments, the scientists trained bees to track a trail of colored marks, as in a scavenger hunt. The bees could then follow—more or less—the same strategy in a completely unfamiliar maze. Amazingly enough, bees can use color in an abstract manner, turning right, for instance, when the branch point is colored blue and left when it is colored green. Individual animals developed quite sophisticated strategies, such as the right-turn rule, that always led to the goal, though not necessarily by the shortest route.
In humans, the short-term storage of symbolic information—as when you enter an acquaintance’s phone number into your iPhone’s memory—is associated with conscious processing. Can bees remember task-relevant information? The gold standard for evaluating working memory is the delayed matching-to-sample (DMTS) paradigm. The subject looks at a picture for a few seconds. The test image then disappears for five or 10 seconds. Subsequently, two pictures are shown next to each other, and the animal has to choose, by pushing a lever or moving its eyes, which of the two images was the test picture. This test can be carried out correctly only if the animal remembers the image. A more complex version, the delayed nonmatching-to-sample (DNMTS) task, requires one additional processing step: choosing the opposite image from the one previously shown.