Part 1

LITTLE BLUE BOOK NO. 720 Edited by E. Haldeman-Julius

The Intelligence of Invertebrate Animals

Maynard Shipley

HALDEMAN-JULIUS COMPANY GIRARD, KANSAS

Copyright, 1924 Haldeman-Julius Company

PRINTED IN THE UNITED STATES OF AMERICA

THE INTELLIGENCE OF INVERTEBRATE ANIMALS

CONTENTS

Page Introduction 5 Earthworms 14 Starfish 17 Sea-Anemones 18 Mollusks 19 Octopi 20 Crustacea 21 Hermit-Crabs 22 Horseshoe Crabs (Limulus) 24 Spiders and Insects 25 Spiders 25 Beetles 35 Wasps 36 Bees 43 Ants 48 Termites (“White Ants”) 54 Conclusion 55

THE INTELLIGENCE OF INVERTEBRATE ANIMALS

INTRODUCTION

No one doubts today that all Vertebrates, from the Fish to Man, possess more or less intelligence--namely, the power of forming memory associations and of learning by experience. But when we come to the study of Invertebrates (e. g., Insects, Spiders, Mollusks, Worms), we meet with much divergence of opinion among the authorities. Many competent investigators have been led to the conviction that the capacity to learn by experience, to form memory associations, leading to intelligent adjustment of behavior to environment, resides only in those animals which possess a true cerebrum and central nervous system, such as is found only in the Vertebrates. Below these forms, they conclude, lie only “instinctive reactions” to stimuli--“purposeful action without consciousness of purpose” (Hartmann). With increasing complexity of the nervous system, arises the neural mechanism for memory association, the basis of intelligence; and to “inherited habit” (instinct) is added deliberate (intelligent) purposeful adaptation of conduct to a consciously desired end, the underlying motive being avoidance of pain and the attainment of pleasure, or satisfaction.

A simple illustration of the modification of mere instinct by associative memory, plus pleasurable or painful effects, is afforded by Lloyd Morgan’s experiments with chicks.

As is well known, no sooner is a young chick hatched than it begins--by instinct--to peck at all sorts of objects of about a certain size, whether they are edible or not. If, however, one of these objects happens to be a caterpillar of nauseous taste, upon meeting a similar caterpillar a second time the chick appears to remember its first painful experience, and refrains from pecking at it, and may even scrape its bill on the ground as if to wipe off the bad-tasting substance, so vividly is it recalled. This is an example of associative memory and “learning by experience,” avoiding the repetition of acts previously attended by pain or displeasure. “What distinguishes intelligence from instinct is,” says Professor Holmes, “that in the latter the connections between acts are based upon hereditary organization, whereas in the former they are established through experience.... We have in this modification of instincts through the pleasurable or painful effects they produce the beginning of intelligence.”

Such notable psychologists as Mach, Loeb, Holmes, Thorndyke, Morgan, Whitman, Baldwin, and many others accept as a criterion of intelligence in animals this capacity for memory association, constituting what the metaphysicians call _consciousness_.

For most modern psychologists, _an interruption of consciousness is merely an interruption of the activity of associative memory_. They speak of the extent of associative memory in the animal kingdom instead of the extent of consciousness among animals.[1]

If an animal possesses the mechanism for associative memory, then it possesses, unquestionably, the mechanism for intelligence. Just what this necessary mechanism is, and in what group of animals it appears in its simplest form, is at present a debatable question--not to say an unsolved problem.

On the positive side, we may assume that if an animal can “learn by experience”--associate the memory of a previous experience with a present situation, and profit by this association--it possesses intelligence.

On the other hand, failure on the part of an experimenter to train an animal to react in a desired way does not afford proof of the absence of intelligence--of associative memory. It may only prove that wrong methods have been employed by the experimenter.

Some authorities have found evidences of intelligent reaction to stimuli, not only in such Invertebrates as the Crab, Crayfish and Horseshoe Crab, but also in the Octopus, Starfish and even among the lowly group familiarly known as “Worms.”

Binet went farther and wrote a learned work on “The Psychic Life of Micro-organisms,” in which considerable intelligence was attributed to Infusorians. But that was thirty years or more ago.

While no competent writer would assert today that psychic life is entirely absent in the Protozoa (one-celled animals), it is now generally conceded that no adequate proof of intelligent response to stimuli among unicellular animals has so far been forthcoming.[2]

In the opinion of the late Dr. Jacques Loeb, the claim of a number of investigators that associative memory and therefore of intelligence as here defined, is possessed by even such multicellular forms as Worms, Starfish, Sea Urchins, Actinians, Medusae and Hydroids, is unwarranted by the experimental data. “Claims for the existence of such memory in these groups of animals,” remarks Loeb, “have frequently been made, but such claims are either plain romance or due to a confusion of reversible physiological processes with the irreversible phenomena of associative memory. The less a scientist is accustomed to rigid quantitative experiments, the more ready he is to confound the reversible after effects of a stimulus--e. g., the effects due to an increase in hydrogen ion concentration--with indications of associative memory. Learning is only possible where there exists a specific organ of associative memory, the physical mechanism of which is still unknown.”

Loeb admitted that associative memory “exists in most mammals,” also in birds. In the lower Vertebrates this capacity, he thought, was only _occasionally_ found: “Tree-frogs, for example, can be trained, upon hearing a sound, to go to a certain place for food. In other Frogs, _Rana esculenta_, for instance, no reaction is as yet known which proves the existence of associative memory. Some Fishes evidently possess memory; in Sharks, however, its existence is doubtful. With regard to Invertebrates, the question is difficult to determine. The statements of enthusiasts who discover consciousness and resemblance to man on every side should not be too readily accepted.”

We must now add, that equal caution should be used in regard to those authors who contend that intelligence does not exist among Invertebrates, but only “instinctive reactions to stimuli.” To describe an act as “instinctive,” moreover, does not explain much. G. Bohn asks: “What is instinct?” and answers: “A word.”

Mr. Garrett P. Serviss recently received a letter from a citizen of Philadelphia from which I quote the following paragraph:

“You speak of the intelligence of the Spider. Understanding and reasoning go hand in hand with intelligence; there is no intelligence without reasoning or understanding, hence it can be applied to Man. How do you apply it to the Spider? So, as regarding the Bee and the Ant, would you not think that their intelligence is simply ‘instinct,’ peculiar to their species for self-preservation?”

Mr. Serviss replied (in part) as follows:

“I see no reason for denying intelligence to animals ranking below Man in the scale. Both the lower animals and the human species possess what are called instincts, which are said to act spontaneously, without the aid of reasoning. No animal, indeed, possesses a greater number of instincts than Man.

“But if the distinction between instinct and intelligence is to be based on the employment of conscious reasoning or intelligence, this faculty cannot be denied to the lower animals, because I believe that many of them do exercise a power of reasoning, i. e., of drawing conclusions from observation.

“Natural history books are full of instances of exhibitions of intelligence by Dogs, Cats, Elephants, Horses and many other creatures. It is true that some naturalists insist that all of the apparently intentional and reasoned acts of such creatures are merely manifestations of instinct, or unconscious responses to external stimuli, but all naturalists are not of that opinion.”

No, they are not.

Prof. S. J. Holmes says: “Psychologists nowadays with comparatively few exceptions agree in regarding intelligence not as a faculty standing in sharp contrast to instinct, as was formerly taught, but as one resting on a foundation of instinct, and gradually growing out of behavior of the purely instinctive type. The term intelligence is used here in the wider sense as embracing all those forms of profiting by experience through the formation of associations. It therefore includes psychic activity ranging from simple associative memory to complex trains of reasoning.”

Paley, in his “Natural Theology,” defines instinct as “a propensity prior to experience and independent of instruction”; while Spencer (“Principles of Psychology”) states that instinct is a “compound reflex action,” which is terse, if not explanatory.

Hartmann’s “purposeful action without consciousness of the purpose” is a contradiction in terms. “Purpose” implies consciousness of end in view. One cannot readily believe that when an Orang-utan builds its platform or “nest” in the boughs of a tree in the jungle it does not purpose (_intend_) to rest and sleep on it; or that when a Beaver cuts down a tree in such wise that it invariably falls in the direction of its _need_ it does not _know_ that it is constructing a hut to live in that will meet the requirements of the situation in a running stream.

Dr. Wm. T. Hornaday, in his authoritative recent work, “The Minds and Manners of Wild Animals,” (1922) says:

“Instinct is the knowledge or impulse which animals or men derive from their ancestors by inheritance, and which they obey, _either consciously or subconsciously_[3] in working out their own preservation, increase and betterment. Instinct often functions as a sixth sense.”

Again: “While avoiding the folly of idealism, we also must shun the ways of the narrow mind, and the eyes that refuse to see the truth. Wild animals are not superhuman demigods of wisdom; but neither are they idiots, unable to reason from cause to effect along the simple lines that vitally affect their existence.... Some animals have more intelligence than some men; and some have far better morals.”

Nevertheless, it is still “correct” to say: “Man alone possesses reason.” Fundamentalists, and even many scientists, find this phrase acceptable. The “Age of Reason” began with the appearance of Man on earth, according to orthodox views. “Instinctive behavior” explains--for many scientists--all acts even of such highly organized creatures as Ants, Bees and Wasps. Below this come “tropisms”--obligatory movements made by the organism as a whole in response to the varied stimuli of its environment.

Then we have the category of “purely reflex” actions of the organism--the definite but unconscious reaction of the organism to stimulation of certain nerve-cells.

In the higher microscopic organisms it is admitted that any one of several reactions to a given stimulus might _occur_, the organism “trying” (unconsciously) one reaction after another, on the hit or miss, or “trial and error” method. Man, of course, learns by some faculty other than “trial and error”--maybe.

Finally, and lowest in the scale of animal evolution, we come to the Amœba, a unicellular organism apparently lacking even in a rudimentary nervous system. But this microscopic speck of carnivorous protoplasm seeks and _pursues_ its zigzagging prey!

While there is no proof that psychic life begins only with pluricellular animals, thus denying any sort of consciousness of purpose to even the highest groups (Ciliata) among unicellular organisms (Protozoa), it must be admitted that no conclusive evidence of the presence of mind in these lowly organisms has yet been presented. I shall therefore turn at once to the Metazoa (many-celled animals) for examples of the intelligence of Invertebrates; beginning with the lowest in which manifestations of mind are said to appear, namely, the Earthworm.

FOOTNOTES:

[1] Cf. Loeb, Jacques, “Comparative Physiology of the Brain and Comparative Psychology,” New York, 1900.

[2] For an excellent discussion of this problem see Holmes, Prof. S. J., “The Evolution of Animal Intelligence,” Pages 63-89, New York, 1911; and Jennings, Prof. H. S., “Behavior of Lower Organisms,” New York, 1906. See also, Day and Bentley, “A Note on Learning in Paramœcium,” _Journal of Animal Behavior_, 1, 67, 1911; and Watkins, G. P., “Psychical Life in Protozoa,” _American Journal of Psychology_, 11, 166, 1900.

[3] Italics mine.

EARTHWORMS

In the preceding introduction it was stated that a certain degree of intelligence had been attributed to animals as low in the scale of evolution as Earthworms. No less an authority than Charles Darwin was responsible for this conclusion.[4] This great naturalist had observed that these lowly creatures had developed the peculiar habit of plugging up their burrows with dead leaves. He noted that leaves were drawn into the burrows by methods best suited to their particular shape. For example, linden leaves were drawn in by their tips, while no attempt was made to pull in leaves of the rhododendron by this method, these leaves being larger at the tip than at their base. On the other hand, pine needles, which frequently occur in pairs, with a common base, were never seized by the small end, since the separated ends of the needles would cause trouble. They were invariably attacked at the compact basal end, which is smaller than the mouth of the burrow.

“Instinct” may guide Worms in this nice discrimination. But Darwin tested them with materials unknown to them or to their ancestors. He cut up paper into triangular forms and placed it at the disposal of the Worms. To his astonishment the brainless creatures almost invariably seized the bits of paper by the most acute angle in carrying them to their burrows. Darwin therefore concluded that an intelligent choice of means to end had been made. Similar experiments were later made by Hanel, and Darwin’s results were verified; but the apparently intelligent reactions of the Worms were interpreted as “more or less complex reflexes in relation to the form and chemical nature of the objects drawn in.” As to which of these two interpretations is more in harmony with the observations, I leave to the reader’s own judgment.

Generally speaking, it is probably best to accept the guiding principle formulated by Prof. Lloyd Morgan, namely, “In no case may we interpret an action as the outcome of the exercise of a higher psychical faculty, if it can be interpreted as the outcome of one which stands lower in the psychological scale.”[5]

Darwin’s conclusion seems to be justified by some experiments quite recently carried out by Professor Heck of the University of Prague, who gathered together for his purpose some five hundred Worms. The Worms were introduced into a passage shaped like a capital T, carved from a block of wood, and covered with a glass plate so that the movements of the animals might be watched. When they came to the junction, about half of them turned one way and half the other. Then the apparatus was arranged so that those Worms which took the left-hand passage received a mild but probably disagreeable shock. At first they did not seem to know what to make of this; but after they had all been through the experience about 200 times, they nearly all took the right-hand turn. When the electrodes were then moved to the right-hand passage, the Worms learned to shift to the left-hand after only 65 trials--evidently showing something beyond the operation of mere chance.

Commenting on this attitude of Earthworms to learn by experience, a writer in _The Scientific American_ (April, 1924) remarks:

“In the human sense, Earthworms have no brains; their nervous systems consist of a series of little ganglions, or nerve centers, on the under side of the Worms and connected with each other by nerve fibers. If the Worms were cut in two, the fragments still showed the ability to distinguish between the safe and the unpleasant road to travel, indicating that the Earthworm remembers in every one of its ganglions, and that it is able to learn and profit by experience.”

In other words, the phenomena of associative memory, hence the capacity to learn by experience, seems to occur not only in animals devoid of cerebral hemispheres--long regarded as the sole seat of intelligence--but in organisms possessing no cerebro-spinal nervous system. In Invertebrates the mechanisms which allow associative memory “will probably be found in the supra-œsophageal ganglion” (Loeb).

“The Earthworm has no specialized sense organs, it has neither eyes to see, nor nose to smell, nor ears to hear with. Still, although it is apparently deaf, it is not devoid of the power of appreciating those stimuli which in us excite the sensation of sight or smell. A strong light suddenly turned on the anterior end of the body will cause the Worm instantaneously to withdraw into its burrow, and Worms readily recognize the presence of such favorite food as onions and raw meat. Their sense of touch is well developed and they are very sensitive to vibrations; for instance, a stamp of the foot on the ground will cause all those in a certain radius to disappear into their burrows. It is further possible that Earthworms possess other senses with which we are totally unacquainted.”[6]

It is quite evident, from what has been said above, that remarkable responses to environmental stimuli are made by animals quite devoid of a brain and lacking in those sense organs popularly assumed to be necessary to such responses of the organism as have just been described.

FOOTNOTES:

[4] See his classical work, “The Formation of Vegetable Mould Through the Action of Worms, with Observations on Their Habits,” New York, 1883.

[5] Cf. Morgan. Prof. C. L., “Animal Life and Intelligence,” 1891; “Habit and Instinct,” 1896; “Animal Behavior,” 1900.

[6] Shipley and MacBride, “Zoology,” 4th Ed., 1920.

STARFISH

Memory, according to Romanes, begins with the Echinoderms--e.g., Starfish, Sea-anemones, etc.; and Preyer’s extensive experiments with Starfish led him to believe that he had “discovered indubitable indications of intelligent action” in the case of Ophiurus (“brittle star”). The question is still under debate, with the weight of authority on the side of Loeb, Jennings, Gaser and others, whose experiments led them to the opposite conclusion.

Thomson finds that Starfish learn to meet new difficulties in new ways. If they cannot surmount their difficulties one way, they will try another.[7]

Starfishes are nearly always hungry and they consider Sea-urchins a delicacy. But Sea-urchins are armed with small but sharp “three-bladed screws” on their backs. Knowing this, the Starfish deliberately strip these blades away and proceeds to devour the Sea-urchin with its elastic mouth.

Holmes observes that “the behavior of Echinoderms is certainly complex and plastic to a remarkable degree,” but he concludes that the power of forming associations in this group is very doubtful.

FOOTNOTES:

[7] See Thomson, Prof. J. Arthur, “Secrets of Animal Life,” 1919.

SEA-ANEMONES

Some authors find evidences of intelligence in the Cœlenterata, which includes Hydroids, Jelly-fish, Sea-anemones, etc. The Sea-anemone, possessing no nerve-ganglia, when dislodged from its partnership with the Hermit-crab will quickly attach itself to the Crab’s leg and again climb up on to the back of the shell, in which the crustacean makes its “home.”

Professor J. Arthur Thomson observes that the Sea-anemone “is in some cases more than quiescent in regard to the partnership,” and adds that while responsiveness to the touch of the Hermit-crab may have come to be ingrained in its early constitution, “it is difficult to think clearly of its racial establishment.”

The behavior of some Cœlenterata, as Holmes remarks, “is often highly plastic and capable of being modified in many ways as the result of previous experience.” This is true also of the Vermes (“worms”) and Echinodermata. “We do not intend to deny the existence of intelligence in the groups mentioned; we think it not improbable that intelligence of a primitive sort may be discovered, at least in the more highly developed members of these divisions; but at the present time we can only grant the Scotch verdict of ‘not proven’.”[8]

FOOTNOTES:

[8] See, on this phase of the subject, Holmes, “The Evolution of Animal Intelligence,” Chapter IX, 1911.

MOLLUSKS

Among the Mollusks, not only the highly organized Cephalopods (Cuttle-fish, Octopus, etc.), but even the lowly Oyster, and the more active Snail and Slug appear to possess associative memory.

Prof. A. H. Cooke (Cambridge Natural History, Vol. III), declares that Oysters can learn from experience. Says he:--

“As soon as an Oyster is taken out of the sea, it closes its shells, and keeps them closed until the shock of removal has passed away, or perhaps until the desirability of a fresh supply of water suggests itself. The men take advantage of this to exercise the Oysters, removing them from the sea for longer and longer periods. In time this has the desired effect; the well-educated Mollusk learns that it is hopeless to ‘open’ when out of the water, and so keeps his shell closed and his gills moist, and his general economy in good condition.”

A certain degree of intelligence has been attributed to Snails. Miss Elizabeth Lockwood Thomson, for example, experimented extensively with these Mollusks and found that they are educable--that they can learn by experience.[9]

FOOTNOTES:

[9] Miss Thomson’s experiments are described in “Behavior Monographs,” Vol. III, No. 3, 1917, Cambridge, Mass.

OCTOPI

Schneider, Uexküll and Kollman all testify that the Octopus possesses at least a rudimentary intelligence. Romanes agrees with these authorities in attributing to this Mollusk “unmistakable evidences of consciousness and intelligence.”[10]

“That Loligo (Octopus) and related higher Cephalopods have an extreme agility, resourcefulness, and caution is already fully recognized by naturalists, though abundant observations and experiments are still much needed,” says Prof. John Muirhead Macfarland, in his “The Course and Causes of Evolution” (1917).

A young Octopus in the Naples aquarium was seen by Schneider to attack a Hermit-crab living within a shell upon which were several Sea-anemones. Upon approaching the Crab the Octopus was stung by the Anemones and quickly retreated. Thereafter it avoided contact with the Crab. It had learned by experience that Anemone-protected Hermit-crabs are “good things to let alone.” In the course of time, however, Octopi learn to extract the Crabs from their shells without being stung by the nettling cells of the Anemones. They also learn to capture large Crabs and Lobsters without getting pinched.

FOOTNOTES:

[10] Romanes, C. J., “Animal Intelligence,” 8th Ed., Page 29, 1904.

CRUSTACEA