Note how simple are the sensory abilities required of the tick. They may have been feeding on reptile blood before the first dinosaurs evolved, but their repertoire of essential skills remains fairly meager. The tick must be crudely responsive to sunlight so she knows which way is up; she must be able to smell butyric acid so she knows when to fall animalward; she must be able to sense warmth; she must know how to inch her way around obstacles This is not asking much. Today we have very small photocells easily able to find the sun on a cloudless day. We have many chemical analytic instruments that can detect small amounts of butyric acid. We have miniaturized infrared sensors that sense heat. Indeed, all three such devices have been flown on spacecraft to explore other worlds—the Viking missions to Mars, for example. A new generation of mobile robots being developed for planetary exploration is now able to amble over and around large obstacles. Some progress in miniaturization would be needed, but we are not very far from being able to build a little machine that could duplicate—indeed far surpass—the central abilities of the tick to sense the outside world. And we certainly could equip it with a hypodermic syringe. (Harder for us to duplicate just yet would be its digestive tract and reproductive system. We are very far from being able to simulate from scratch the biochemistry of a tick.)
What would it be like inside the tick’s brain? You would know about light, butyric acid, 2,6-dichlorophenol, the warmth of a mammal’s skin, and obstacles to clamber around or over. You have no image, no picture, no vision of your surroundings; you are blind. You are also deaf. Your ability to smell is limited. You are certainly not doing much in the way of thinking. You have a very limited view of the world outside. But what you know is sufficient for your purpose.4
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There’s a thump on the window and you look up. A moth has careened headlong into the transparent glass. It had no idea the glass was there: There have been things like moths for hundreds of millions of years, and glass windows only for thousands. Having bumped its head against the window, what does the moth do next? It bumps its head against the window again. You can see insects repeatedly throwing themselves against windows, even leaving little bits of themselves on the glass, and never learning a thing from the experience.
Clearly there’s a simple flying program in their brains, and nothing that allows them to take notice of collisions with invisible walls. There’s no subroutine in that program that says, “If I keep bumping into something, even if I can’t see it, I should try to fly around it.” But developing such a subroutine carries with it an evolutionary cost, and until lately there were no penalties levied on moths without it. They also lack a general-purpose problem-solving ability equal to this challenge. Moths are unprepared for a world with windows.
If we have here an insight into the mind of the moth, we might be forgiven for concluding that there isn’t much mind there. And yet, can’t we recognize in ourselves—and not just in those of us gripped by a pathological repetition-compulsion syndrome—circumstances in which we keep on doing the same stupid thing, despite irrefutable evidence it’s getting us into trouble?
We don’t always do better than moths. Even heads of state have been known to walk into glass doors. Hotels and public buildings now affix large red circles or other warning signs on these nearly invisible barriers. We too evolved in a world without plate glass. The difference between the moths and us is that only rarely do we shake ourselves off and then walk straight into the glass door again.
Like many other insects, caterpillars follow scent trails left by their fellows. Paint the ground with an invisible circle of scent molecule and put a few caterpillars down on it. Like locomotives on a circular track, they’ll go around and around forever—or at least until they drop from exhaustion. What, if anything, is the caterpillar thinking? “The guy in front of me seems to know where he’s going, so I’ll follow him to the ends of the Earth”? Almost always, following the scent trail gets you to another caterpillar of your species, which is where you want to be. Circular trails almost never occur in Nature—unless some wiseacre scientist shows up. And so this weakness in their program almost never gets caterpillars into trouble. Again we detect a simple algorithm and no hint of an executive intelligence evaluating discordant data.
When a honeybee dies it releases a death pheromone, a characteristic odor that signals the survivors to remove it from the hive. This might seem a supreme final act of social responsibility. The corpse is promptly pushed and tugged out of the hive. The death pheromone is oleic acid [a fairly complex molecule, CH3(CH2)7CH = CH(CH2)7COOH, where = stands for a double chemical bond]. What happens if a live bee is dabbed with a drop of oleic acid? Then, no matter how strapping and vigorous it might be, it is carried “kicking and screaming” out of the hive.5 Even the queen bee, if she’s painted with invisible amounts of oleic acid, will be subjected to this indignity.
Do the bees understand the danger of corpses decomposing in the hive? Are they aware of the connection between death and oleic acid? Do they have any idea what death is? Do they think to check the oleic acid signal against other information, such as healthy, spontaneous movement? The answer to all these questions is, almost certainly, No. In the life of the hive there’s no way that a bee can give off a detectable whiff of oleic acid other than by dying. Elaborate contemplative machinery is unnecessary. Their perceptions are adequate for their needs.
Does the dying insect make a special last effort to generate oleic acid, to benefit the hive? More likely, the oleic acid derives from a malfunction of fatty acid metabolism around the time of death, which is recognized by the highly sensitive chemical receptors in the survivors. A strain of bees that had a slight tendency to manufacture a death pheromone would do better than one in which decomposing, disease-ridden dead bodies were littering the hive. And this would be true even if no other bee in the hive were a close relative of the recently departed. On the other hand, since they are all close relatives, special manufacture of a death pheromone can be understood perfectly well in terms of kin selection.
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So here’s a bejeweled insect, elegantly architectured, prancing among the dust grains in the noonday sun. Does it have any emotions, any consciousness? Or is it only a subtle robot made of organic matter, a carbon-based automaton packed with sensors and actuators, programs and subroutines, all ultimately manufactured according to the DNA instructions? (Later, we will want to look more closely at what “only” means.) We might be willing to grant the proposition that insects are robots; there’s no evidence, so far as we know, that compellingly argues the contrary; and most of us have no deep emotional attachments to insects.
In the first half of the seventeenth century, René Descartes, the “father” of modern philosophy, drew just such a conclusion. Living in an age when clocks were at the cutting edge of technology, he imagined insects and other creatures as elegant, miniaturized bits of clockwork—“a superior race of marionettes,” as Huxley described it,6 “which eat without pleasure, cry without pain, desire nothing, know nothing, and only simulate intelligence as a bee simulates a mathematician” (in the geometry of its hexagonal honeycombs). Ants do not have souls, Descartes argued; automatons are owed no special moral obligations.
What then are we to conclude when we find similar very simple behavioral programs, unsupervised by any apparent central executive control, in much “higher” animals? When a goose egg rolls out of the nest, the mother goose will carefully nudge it back in. The value of this behavior for goose genes is clear. Does the mother goose who has been incubating her eggs for weeks understand the importance of retrieving one that has rolled away? Can she tell if one is missing? In fact, she will retrieve almost anything placed near the nest, including ping-pong balls and beer bottles. She understands something, but, we might say, not enough.If a chick is tied to a peg by one leg, it peeps loudly. This distress call makes the mother hen run immediately in the direction of the sound with ruffled plumage, even if the chick is invisible. As soon as she catches sight of the chick, she begins to peck furiously at an imaginary antagonist. But if the fettered chick is set before the mother hen’s eyes under a glass bell, so that she can see it but not hear its distress call, she is not in the least disturbed by the sight of him. … The perceptual cue of peeping normally comes indirectly from an enemy who is attacking the chick. According to plan, this sensory cue is extinguished by the effector cue of beak thrusts, which chase the foe away. The struggling, but not-peeping chick is not a sensory cue that would release a specific activity.7