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.

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.

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: