The Nature of Learning in Animals

Administrator2 · Jul 6, 2002

PAUL OF EUGENE

The following material is relevant to the discussion Helen and I are having on the nature of learning in animals. I think it is very interesting, fun to read, and I hope you will see fit to add it on for information purposes and perhaps as a spark to discussions. The rest is all quoted material.

From The Territorial Imperative by Robert Ardrey, C. 1966, p 327 and following

…the planarian worm is an aquatic creature so primitive in the evolutionary scale that it lacks a true central nervous system, possesses a brain consisting of nothing but two enlarged ganglia connecting its two lateral nerves, lacks a stomach or rectum or anything resembling a modern digestive system, and while capable of laying an egg is equally capable of dividing itself in two and growing a new head on the front of its old rear section. Since it can grow that head in six days, we may safely assume that the planarian’s brain is an organ of no great planarian concern. And we may also assume that had the planarian worm been a creature of natural invention at any time in the last half billion years, it would have incorporated into its old-fashioned architecture a modern gadget or two. It therefore seems likely that the creature is a leftover from those hazy pre-Cambrian days of evolving life about which we know so little. But when we say that, we talk of ages belonging to the same time scale as that which absorbs the cosmologist. When we look at the planarian we are looking back into the history of life, just as when we observe a quasar we are looking back into the history of all things.

Jay Boyd Best and his colleague Irvin Rubinstein began their Washington experiments with the planarian in 1958. Their initial interest was to discover just how much such an all-but-brainless being could be taught. Most learning-and-memory experiments with the planarian have had a weakness, that the learning has been a matter of inducing a conditioned reflex, the all-purpose tool kit of most American psychologists. But this kind of learning, called "classical conditioning", is losing ground among our more advanced observers of behavior. What intrigued Best was that higher accommodation called "instrumental learning" by which, in pursuit of a desirable goal involving choice of actions, one learns to choose the correct path and reject the wrong. A creature as simple as the planarian worm might conceivably be "taught" by electric shock a reflex to avoid this and accept that. But could this primitive being lacking sex, rectum circulatory system, a modern nervous hookup, a brain that could not be regrown in a few days, learn to choose between the rewarding and the unrewarding? And if so, what was he choosing with?

It took little effort for Best and Rubinstein to demonstrate that the worm could not only learn to choose, but could learn with dismaying aptitude. They constructed a plastic maze, a simple device with a Y-shaped channel connecting three wells. A worm would be placed in one well of the flooded maze, then the water would be drained out. Since the planarian cannot long survive in a dry condition, he would crawl out of the well into his tunnel in search of water. But the Y-shaped tunnel forked. The worm faced two choices. Now the observers would brightly light the well at the end of one branch of the fork and leave the other in darkness. If the worm chose the lighted well, the maze would be instantly flooded as a reward.

A training session for a worm consisted of ten or fifteen trials, and the sessions were held every other day. To take account of any innate preference for light or dark, half of the worms were trained to seek the bright well for water, half the darkened. To eliminate any directional prejudices based on right and left, which well to be illuminated was determined by chance. At the first day’s session all worms chose by chance; success or failure was fifty-fifty. But even at the second session preferences developed; those being trained to move toward light did so more often than toward dark; those being trained to move toward dark did so more often than toward light. By the third session – a speed of learning difficult to believe – most worms hit their peaks and chose correctly four times out of five. Then came out of nowhere the incredible collapse.

It is at this moment that we, like the observers, enter the haunted house of psychological beginnings. Almost without exception every planarian worm, once he attained a success of about 80 percent, began choosing the wrong road in preference to the right. That he "knew" what he was doing was inarguable. Had he simply forgotten his lessons, he would have relapsed to the fifty-fifty original score, determined by chance. But he did not. He dropped to one out of three. He was discriminating against the right choice.

Best describes himself and his colleagues as being appalled. They must have been. It is a great enough mystery that such a creature could learn anything. It is an accomplishment defying one’s understanding that he could learn so rapidly. But that on the verge of total success the planarian worms should uniformly embrace perversity lies entirely beyond explanation. And to make matters worse, further trials brought rejection not only of the right answer, but of the experiment itself. When the maze went dry the worms curled up, refused to go anywhere, and in arrant rebellion opted for inevitable death in preference to further learning.

The harried investigators, faced by the organic equivalent of apples falling upward and straight lines turning corners, bumbled about trying to find ways of appeasing their tiny rebels, who by now had taken charge of the experiment. Perhaps there was something about the kind of plastic used in molding the maze that made the worms unhappy. They found other materials. The worms remained unmoved. Perhaps the mere threat of death in a draught was not enough and the worms were on strike for inexpressible fringe benefits. The scientists added that supreme planarian delicacy, finely chopped liver, to the water in the wells which they were supposed to crawl to. The worms remained adamant, muttering some planarian equivalent of "The hell with it". By this point in the experiment it was not the mentality of the worms being tested but the sanity of scientists, and hysteria hovered close by. When somebody wondered if the worms might have been suffering from claustrophobia, hysteria seemed, in truth, to have closed in. Another maze was built. It offered not merely water-filled wells to save worm life but a new spaciousness at worm’s end, a sense of freedom and elbow room where a worm could feel like a worm. And lo! It worked. It had been claustrophobia. The worms cooperated.

Any scientist in his right mind would with this climax assume that he had seen everything. But by now both Best and Rubinstein had long since lost touch with their right minds. They became infatuated with the possibility that worms who could suffer from claustrophobia might also have suffered boredom from a lesson so easily mastered. Fortunately for the future of psychology there was no one present to point out to the two mad scientists that a creature lacking proper brain, proper nervous system, proper belly, proper sex life, and even proper rectum has nothing under the sun to get bored with. Since no one was looking, they constructed another maze, an exact duplicate of the original, but made of rough plastic instead of smooth.

Now they started the same experiment all over again. They used the smooth maze as before. They trained their worms to head for brightened or darkened wells, each as loaded with claustrophobia as the wells had been in the first place. Predictably, when the worms hit a level of 80 percent success they promptly went into a decline and started choosing wrong answers. But now the scientists clapped them in the maze that would feel rough on their undersides as they crawled along. From that day on, half of the trials were conducted in the smooth maze, half in the rough. A worm had to learn that if he felt smooth plastic against his undersides he must head for the light to reach water, but if he felt himself crawling over rough plastic then to gain water he must head for the dark. In the testing of monkeys and children this is known as the double-ambiguity problem.

One out of every three planarian worms mastered the double-ambiguity problem. Sometimes when they reached the fork they would hesitate, pointing their heads first one way then the other, as if trying to make up their "minds". In animal study this is known as "vicarious trial-and-error behavior." Sometimes, unable to make up their "minds", they would go back to the starting point and begin again. But of the one out of every three who succeeded in mastering the whole problem, none ever grew bored again. None ever showed perversity, none ever rebelled, none ever curled up in tight defiance or muttered, grimly, the hell with it.

Where are we? What forces do we behold when we inspect the mind of worm or man? What is this everlasting scenery that graces our stages? What are these staircases that life has always climbed? What are these beds that life has always slept in, these antique furnishings that seem forever to have been life’s own? We do not know. Our ignorance of the human being is as massive and as measurable as our ignorance of the planarian worm. We are equivalent mysteries, and the man who says otherwise is the supreme ignoramus among us.
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Administrator2 · Jul 8, 2002

HELEN

Fascinating, Paul. I looked all over the net for any followup material on this and only found some kids' science fair projects mentioned (but not even explained). Has there been anything done since 1966 on this?

Administrator2 · Jul 9, 2002

PAUL OF EUGENE

Alas, I don't have anything more to add about planarian worms. But I have some ideas further evaluation of them, tho in the course of my non-experimental day job I'll never have time or opportunity myself . . .

Today, with our better equipment, can we disect the worms cell by cell and count their nerve cells, and measure any differences between trained worms and untrained worms?

Can we simulate the nerve cell connections and thereby duplicate the behavior of the worms in a computer simulation?

I suspect that there has been little follow up because psychology lacks a general theory of consciousness and awareness. Not that I count worms as being conscious or aware but rather that experimental psychologists lack a theoretical framework around which to develop further experiments.

That's just a fancy way of repeating that we are ultimately vastly ignorant about these things.

Administrator2 · Jul 12, 2002

HELEN

I agree that we are ignorant of a great many things, Paul. Let me at least ask this -- where did you get the information you posted? It does not seem to be written the way I would expect in a regular journal but seems instead to be some kind of popularized account. Is there any verification of this material itself that can be referenced? As I said, I could not find anything about it on the web.

In the meantime, having worked somewhat with animals in both a psychology lab and in our own home, I would venture to say that there is a difference between what we might call conditioned responses and the type of learning involved when we train a dog or horse (PLEASE don't talk to me about training cats! They train us!). And all that is in turn, in my opinion, gapingly apart from intellectual learning that takes place with humans.

Administrator2 · Jul 13, 2002

PAUL OF EUGENE

The book is "The Territorial Imperative" by Robert Ardrey. You can buy it today - here's a link to that book at Amazon.com.

http://www.amazon.com/exec/obidos/ASIN/1568361440/inktomi-bkasin-20/002-4632614-2525634

The excerpt I quoted is typical of Ardrey's interesting and lucid writing style. Note how much of the experiment he manages to convey and still keep the reader interested all the way through. You can learn a lot about animal morality, evolution, and such, in spite of its age. Please consider adding it to your library! There are some books that simply wear well with time and this is one of them. The story of the experiments on planarian worms is NOT the main thrust of the book, which is how the theme of territory plays out across multiple species, including man. I just thought the experiments he so eloquently described were interesting.

Now its only fair to warn you Ardrey's work is strongly pro-evolution and he directly states time and again positions you have opposed. Think of it as an investment in learning what the other side thinks like.

I know what you mean about cats! I have observed cats in my back yard who are very indignant that I don't feed them and water them. Seemingly, once in a while the cats issue a "deed" to my house and then the winning cat comes over to claim his just dues, free food and water and medical care from us humans that live in his house. We don't have pets or keep pets and the cats eventually give up.

Starlings nest in our neighborhood every spring. Until we put up a permanent grill, a pair would always try to nest the the drier vent hole, which is up under the eave. Two different years, a pair started doing this and we stuffed newspaper in the hole to block them. One year the birds kept hanging around, seeming trapped in attachment to the location for the longest time and then finally gave up and we presume nested elsewhere. The next year, a cute young couple started to nest there again and we stuck the newspaper up there again and apparantly they complained to somebody in authority, because an older, larger starling came over and looked over the whole situation very carefully. This couple did not take near as long to give up and go elsewhere.

Sure looked like a little bit more than mere conditioned response was going on to me!

Administrator2 · Jul 14, 2002

HELEN

Paul, hi again! I did not say that conditioned responses were all that animals had. I said they were different from what we call learning where training some animals is concerned and certainly different from the intellectual learning we give our children and, hopefully, continue ourselves.

As far as the planaria are concerned, I would want to see some kind of official write-up, at least, of what happened. I would want to try to duplicate it or see it duplicated. This is the sort of thing which is wide open to both testability and falsifiability, and that should be done for it to be verified. Fascinating tales are great, but they do not always give the facts necessary for determining what was actually going on.

And yes, the birds learned. I have no doubt about that. But it is still a wee bit different from studying and passing a test on the history of the Roman Empire…

Administrator2 · Jul 16, 2002

PAUL OF EUGENE

At Helen's request I checked out Ardrey's footnotes and his book provides the following reference on the quote I provided above as his source:

Best, Jay Boyd: "Protopsychology", Scientific American, Feb 1963

Administrator2 · Jul 18, 2002

HELEN

Thank you Paul. I am wondering, if this experiment was actually as reported, why it did not inspire a whole host of repeats and further experiments with other very simple life forms?

I am going to try to get hold of the original article. The implications of learning and "preferences" without a brain are fascinating.

If this is indeed true of planaria, then when one is cut in half so that a new half regenerates, would both new planaria then 'remember' what the original learned?

I can't believe the implications of this have slipped by the scientific establishment!

The Nature of Learning in Animals

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The Nature of Learning in Animals

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